ISRM 2023 - PUBLICATIONS

T18: Early Career Forum (Young Researchers)Andor NÉMETH, Ákos TÖRÖKBudapest University of Technology and Economics, Faculty of Civil Engineering, Department of Engineering Geology and Geotechnics, Budapest, HungaryMechanical behavior of granitic rocks under elevated temperatures: implications for underground radioactive waste disposal safety and tunnelling1999 The study focuses on heat-induced physical property changes ingranitic rocks, which are vital for the stability of underground spaces such as tunnels or radioactive waste disposal chambers. Monzogranite from Bátaapáti Radioactive waste repository was tested at different temperatures (22 °C, 250 °C, 375 °C, 500 °C, 625 °C, 750 °C) for P and S-ultrasound velocities, bulk density, Duroskop rebound, uniaxial compressive strength, and modulus of elasticity. Analysis revealed temperature-related physical deterioration via test results. Significant changes occurred above 500 °C, and physical deterioration of the monzogranite was drastic at 750 °C. This data could predict the heating temperature in granitic rocks under unknown conditions, aiding the design and global monitoring systems. | radioactive repository, granite, heat treatment, mechanical properties
Keynote lectureNiketa UKAJ, Christian HELLMICH, Stefan SCHREINERInstitute for Mechanics of Materials and Structures, TU Wien, Vienna, AustriaThe Mechanics of Pandemics: Empowering Boltzmann creep for the prediction of COVID-19 fatality trends1000 Ever since Boltzmann’s landmark paper from 1874, integro-differential equations for viscoelasticity have been a cornerstone for reliable quantification of the time-dependent response of solid mechanical systems: their creep strains depend on the accumulated effect of all load events having taken place before. This naturally includes rock mechanics, both as regards its narrower meaning of rock creep testing, and its broader sense of creeping tunnel support systems such as shotcrete shells in the context of the New Austrian Tunneling Method. When the COVID-19 pandemic evidenced often sobering performance of traditional epidemiological models [where the system response only depends on the current state of the system, and not on the entire history], the question arose whether the Boltzmann integro-differential equations may be as efficient for “virus loads”, as they have proved to be for classical mechanical loads. Evaluating infection and fatality data from more than 100 countries, this question was affirmatively answered. Here we go one step further, and discuss recently obtained results for “aging pandemics” in analogy to aging creep experienced in shotcrete systems where the material maturation due to the hydration reaction evolves at a similar pace as the creep strains do. We observe exponentially decaying fatality rates throughout the first thousand days of the COVID-19 pandemic, with a characteristic time of around 180 days in the case of Austria. | SARS-CoV-2, COVID-19, concrete creep, viscoelasticity, integro-differential equations, optimization
T12: New developments in rock supportManuel ENTFELLNER, Helmut WANNENMACHERImplenia Österreich GmbH, AustriaNew yielding elements made of high-strength expanded polystyrene (HS-EPS)1100 Yielding elements as a part of the shotcrete lining represent state-of-the-art tunnelling in overstressed weak ground conditions. These elements avoid overstressing of the shotcrete lining during the early curing process, where the displacement rates are highest and the shotcrete strength/stiffness lowest. A novel yielding element of High-Strength Expanded Polystyrene (HS-EPS) is introduced, which overcomes existing systems’ drawbacks. This innovative system is lightweight and allows for rapid installation. Furthermore, the modular setup of the element permits an easy on-site adaption to react to in-situ deformation patterns and changing ground conditions. Recent experiences from applications in alpine base tunnels in overstressed weak ground conditions are presented. | Tunnelling, Yielding Principle, Overstressed Weak Ground, Squeezing Ground, Yielding Elements, HS-EPS
T13: Numerical methods in rock engineeringMyong Song SONG (1), Un Chol HAN (2), Kun Ui HONG (1), Il Yong KANG (2), Yong Il RI (3)1: Faculty of Mining Engineering, Kim Chaek University of Technology, Democratic People's Republic of Korea (North Korea); 2: School of Science and Engineering, Kim Chaek University of Technology, Democratic People's Republic of Korea (North Korea); 3: Faculty of Anthracite Mining Engineering, Pyong Song University of Coal Mining, Democratic People's Republic of Korea (North Korea)Forecast of Mine Inflow using In-situ Well Test and Visual Modflow in an Underground Mine1102 Water inrush in mining field is considered as one of the major dangerous factors for production safety and worker’s life in coal mines. In this paper for underwater flow, repeat measurements of water level is essential to water inrush forecasting, so the control point drawdown must be clearly calculated in accordance with the mining construction plans, dewatering period and drainage time. We determined optimal parameters in relation to the water inrush forecasting using the PEST-ASP module in Visual MODFLOW in order to get accurately the groundwater flow distribution at the control points, including normal and maximum water inrush. Comparing simulation results and in-situ data of water inrush, the relative error was lower than 0.74%, showing that this method is the most reasonable one for forecasting water inrush in a coal mine. | Numerical Simulation, water Inrush, Visual MODFLOW, Pumping well
T16: Underground storage for liquid and gaseous mediaDuo WANG (1,2), Xiao LI (1), Hang YUAN (3), Guanfang LI (1)1: Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China; 2: SINOPEC Petroleum Exploration and Production Research Institute, Beijing, China; 3: School of Geophysics and Information Technology, China University of Geosciences, Beijing, ChinaShale gas accumulation mechanism in the shallow burial depth: Insights from mechanical properties and methane adsorption capacity1105 The shallow burial depth shale gas reservoirs have great significance for low-cost development. Petrophysical characteristics and methane adsorption capacity are fundamental factors that control shale gas enrichment. We investigated petrophysical characteristics and methane adsorption capacity based on lithology and burial depth. Several samples from reservoirs and sealing formation were analyzed to elucidate the enrichment mechanism, applying N2 and CH4 adsorption, petrophysical test, and micro CT scanning. The results indicate that the combination of high clay content calcareous siltstone and shale has obvious sealing capacity comparing to siliceous shale, and less fractures could be induced because of uplift. Besides, a shallow shale gas enrichment model was proposed, methane adsorption capacity is highly related to the burial depth, in the ultra-shallow depth (<700 m), a rapidly decreasing trend can be observed under a normal pressure condition, while there is no obvious decline of the adsorption capacity in the overpressure reservoirs. | shallow shale gas; enrichment mechanism; petrophysical characteristics; methane adsorption
T13: Numerical methods in rock engineeringMansour SHARAFISAFA (1,2), Zeinab ALIABADIAN (1), Akira SATO (1), Luming SHEN (2)1: Graduate School of Science and Technology, Kumamoto University, Japan; 2: School of Civil Engineering, The University of Sydney, Sydney, AustraliaFDEM modelling of hydraulic fracturing in jointed rocks1106 Hydraulic fracturing has been widely used in tight reservoirs to generate fractures to improve conductivity and productivity. However, presence of discontinuities such as joints, faults, bedding, and cementations, the complex interaction between the HFs and theses geological features influences the efficiency of an injection treatment. Considering the mechanical differences between natural fractures (NFs) and rock matrix, the type of interaction varies and demands a detailed study to explore such behaviour, specifically for the filled joints. In this study, the combined finite-discrete element method (FDEM) is used to investigate the influence of the pre-existing joints and their filling material on hydraulic fracture (HF) propagation. The coupled hydromechanical model is used to allow for the fluid flow through the rock mass. Models with some filled joints are built and HF propagation is modelled to investigate the interaction type. The results reveal strong influence of the fillings on the HF interaction and propagation. | FDEM, Hydraulic fracture, Filled joints, Interaction
T05: Digitalization & AutomatisationMingliang ZHOU (1), Le ZHANG (2), Jiayao CHEN (3), Minglun TAN (2), Hongwei HUANG (1)1: Tongji University, Shanghai, People's Republic of China; 2: Qingdao Guoxin Jiaozhou Bay Second Submarine Tunnel Co., Ltd., Qingdao, China; 3: College of Civil Engineering, Beijing Jiaotong University, Beijing, ChinaQuantitative Risk Assessment of Rock Tunnel Faces Using Stacked Deep Learning and Multi-Source Data1110 Quantitative tunnel face risk assessment is the characteristic challenge of rock tunnel excavation projects. This study establishes a multi-source database and proposes a stacked deep learning method for the quantitative tunnel face risk assessment. Both contact and non-contact methods are used to collect various data sources such as face images, site geological information, and rock mass properties. Thirteen multi-source variables describing the rock tunnel faces were considered as inputs, and Rock Mass Rating (RMR) system was adopted to generate the target output. The proposed model architecture combines a range of well-performing models to make accurate predictions of the tunnel face rock mass rating. Overall, this study establishes a comprehensive tunnel face risk assessment framework that leverages various data sources and stacked deep learning. The experimental results from a tunnel project in China demonstrate that our stacking deep learning model performs well in assessing rock tunnel face stability. | Rock tunnel, Face stability, Machine learning, Risk Assessment, Multi-source Data
T03: Deep geothermal energyYandong YANG (1,2), Duli YAN (1), Feifei HUANG (1), Hualin LIAO (2)1: Yan‘an University, People's Republic of China; 2: China University of Petroleum (East China）Hot dry rock breaking with PDC bit under various of impact loads1111 Deep dry hot rock geothermal energy is a new type of renewable energy, which is environmental friendly and abundant. The ROP improvement is one of the bottleneck faced in deep hot dry rock drilling. Regarding to the high temperature, strength of hot dry rock, the combination of downhole impact drilling tools and PDC bits has become an effective method to increase the ROP of hot dry rock, and the waveform of the impact load generated by percussive drilling tool is an important factor influencing the ROP of the hot dry rock. Therefore, a 3D polycrystalline diamond compact (PDC)bit-hot dry rock model is established, in order to evaluate the ROP of dry hot rock under the coupling of impact loads. The research results shows that ROP improvement rate of rectangle impact load is the best，which could provide a theoretical basis for the design of rock breaking percussive drilling tool. | Hot dry rock, percussion drilling, rock breaking, energy transfer efficiency, impact load
T04: Deep mining and tunnellingSanjay SINGHHarmony Gold, South AfricaDynamic response of the rock mass where the orebody dip changes1113 Mining at depth in a South African gold mine, poses common risks and hazards. Many seismic events have, in the past and present, resulted in the loss of life of several employees. Most of these were inexplicable, and no consideration was given in any study where the orebody being normally weaker in relation to the surrounding rock mass is a result of a catastrophic event, merely by the change in its dip. From the investigations it was deduced that when there is a change in the dip of the orebody the surrounding rock mass characteristics allow the orebody to behave in a similar manner as a steeply dipping fault. The following is an attempt to set the scene, analyze and draw conclusions when an orebody dip changes and thus ensuring the transfer of knowledge. | Dynamic, response, rock, orebody, dip, change
T15: Rock and rock mass propertiesSrđan KOSTIĆJaroslav Cerni Water Institute, SerbiaEstimation models for deformability of marlstones based on their physical and mechanical properties and for variable load range1114 In present paper we establish the correlation between the field determined values of elasticity E and deformability modulus D of marlstones and their laboratory determined physico-mechanical properties. Laboratory results which are taken into consideration are the following: unit weight, moisture content, uniaxial compression strength, cohesion, friction angle, maximum and minimum pressuremeter load range, as input parameters, and elasticity and deformability modulus as output parameters. Statistically significant correlations are determined by applying multiple linear regression method and ANOVA test. Established correlations indicate that both for E and D properties for undisturbed rock samples (cohesion, unit weight, uniaxial compression strength) do not have significant effect, while friction angle has strong positive effect both on E and D. Mostiure content have negative effect on E and D. Minimum/maximum load stress have opposite effect on E and D, meaning that deterioration of rock mass in situ with the increase of stress has negative effect on D. | pressuremeter, marlstone, elasticity modulus, deformability modulus
T13: Numerical methods in rock engineeringHamza MHAMDI ALAOUI, Richard GIOT, Dimitri PRÊT, Philippe COSENZA, Stephen HEDANIC2MP, Université de Poitiers, CNRS, HydrASA, Poitiers, FranceNumerical modelling of the swelling of clayey geomaterials by a multiscale approach1115 The swelling of clay materials finds its origin at the different scales and is governed by two phenomena: crystalline and osmotic swelling. In this work, we propose a multi-scale numerical model that considers both swelling regimes. The model in its first version is based on a phenomenological approach to formulate the different interactions that occur in the interlayer space with respect to the disjoining pressure and the interparticular pores considering capillarity effects. The model is newly implemented in Code_Aster Finite Element software for hydro-mechanical coupling. The aim of this paper is to enhance the first model at its first implementation by adding: interparticular osmotic swelling along with the first existing aspect namely the capillarity effects at the interparticular pores scale. The validation of the updated model focuses on the swelling mechanism existing in constant-volume conditions in terms of swelling pressure. The model showed good accuracy compared to experimental results. | Multi-scale modelling, Disjoining pressure, Homogenization, Osmotic swelling, Clay minerals
T10: MonitoringKazuo SAKAI (1), Toshifumi AKAKI (1), Yoshimi OHNISHI (1), Shigeru TANAKA (2), Tomonori HORIDOME (2)1: Taisei Corporation, Japan; 2: Toa Elmes, JapanDevelopment of tunnel pre-displacement measurement method by fiber optic sensing1117 The authors developed a measurement method by the fiber optic sensing which can evaluate vertical and lateral displacements ahead of the tunnel face. The method uses some fiber optic cable sensors named All Grating Fibers capable of evaluating the longitudinal strains along the cable with high positional resolution and accuracy by the Optical Frequency Domain Reflectometry method. The cable sensors are fixed with inflatable packer tubes in a square pipe inserted in a steel forepole drilled from the face and can be retrieved after the measurement. One advantage is therefore the fact that fibers can be repeatedly used in other pipes. This paper outlines the developed tunnel pre-displacement measurement method by the fiber optic sensing. Results of laboratory experiments and field measurements conducted in a motorway tunnel construction project are also presented. | Pre-displacement measurement, Fiber optic sensing, All Grating Fiber, Optical Frequency Domain Reflectometry
T13: Numerical methods in rock engineeringShahriyar HEIDARZADEH (1), Ali SAEIDI (2)1: SNC-Lavalin, Canada; 2: University of Quebec at Chicoutimi (UQAC)Numerical Modelling-Based Methodology for Generating Fragility Curves of Underground Tunnels under Static Loading1119 We present a method to assess the robustness of underground tunnels against brittle failure by creating vulnerability functions based on rock mass quality and static loading intensities. Using a Monte Carlo Simulation and FLAC3D, we simulated multiple models of a tunnel in rock masses with varying qualities and subjected to different static loads. Fragility curves were constructed using a stress-based failure criterion to measure the severity of brittle damage. Mathematical approximations were used to generate vulnerability functions linking occurrence probabilities of damage states to loading intensities. Results showed that fragility curves offer a numerically developed tool for design engineers to predict different damage states based on variations in rock mass quality and in situ stress state. | Fragility curves, underground tunnels, vulnerability functions, brittle damage, FLAC3D
T13: Numerical methods in rock engineeringKe GAO (1,2), Weibing CAI (1,2), Shugang AI (1,2)1: Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, Guangdong, China; 2: Department Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology, Southern University of Science and Technology, Shenzhen, Guangdong, ChinaA continuum-oriented finite-discrete element method (cFDEM) for rock fracturing simulation1122 The combined finite-discrete element method (FDEM) has been extensively used for rock fracturing simulation. The zero-thickness intrinsic cohesive elements are commonly implemented in FDEM and pre-inserted in the rock model between adjacent finite elements prior to simulation. However, because of the different constitutive laws for cohesive and finite elements, the rock model domain may deform like a discontinuum in the elastic stage (abbreviated as dFDEM). This could cause unrealistic material deformation and also reduce computational efficiency. Here, we propose a novel node binding algorithm to ensure the continuum behavior of materials prior to fracture onset (abbreviated as cFDEM), which can also automatically achieve the explicit separation of fracture surfaces without using complex node splitting algorithm. We validate the robustness of the proposed cFDEM and demonstrate its advantage compared to dFDEM. The work provides a novel perspective for rock fracturing simulation in FDEM. | Combined finite-discrete element method (FDEM), Node binding algorithm, Rock fracture, Numerical simulation, Cohesive zone model
T15: Rock and rock mass propertiesJørgen Steen STEENFELTCOWI, DenmarkOptimization of UCS testing of limestone rock1123 Assessment of strength and stiffness of rock is difficult due to the huge variability in these parameters. This is due to the often very heterogeneous nature of the rock. As large-scale testing is often prohibitively expensive or difficult to achieve in practice, the assessment relies on testing smaller specimens, typically from boreholes. The current paper provides guidelines for evaluation and interpretation of rock strength and stiffness based on UCS, Point Load and Brazil tests as a function of size, height/diameter ratio of specimen and rock strength. Based on currently available standards and literature the empirical conversion equations for tests with non-standard D and H/D values are referenced and evaluated. | Limestone strength, UCS, height/diameter ratio, non-standard specimens
T15: Rock and rock mass propertiesYadong XUE (1), Lushan SHU (1), Kai SHEN (2), Yongfa GUO (3)1: Department of Geotechnical Engineering College of Civil Engineering, Tongji University, Shanghai, China; 2: School of Civil Engineering, Central South University, Changsha, China; 3: China Railway Eryuan Kunming Survey, Design and Research Institute Co., Ltd, Kunming, ChinaStudy on the mechanical characteristics of rock-concrete Brazilian disc based on DEM1125 The rock-concrete interface is usually considered the weakest structural zone in tunnel lining structures. To study the tensile failure of the rock-concrete interface, the Brazilian splitting tests were carried out on sandstone-concrete Brazilian discs using the digital image correlation (DIC) system. The laboratory tensile strength and failure process are consistent with numerical simulation. Then, the tensile behavior of the interface with different roughness was simulated using MatDEM software. Results show that the tensile strength of rock-concrete disc is insensitive to the sawtooth number. The tensile strength increases with increasing sawtooth angle due to increasing total contact area and interlocking effect. When the sawtooth angle is more than the critical value, the tensile strength increases rapidly due to the formation of the breaking sawtooth. | Rock-concrete interface, Brazilian splitting test, Interface tensile failure, Interfacial roughness, MatDEM
T13: Numerical methods in rock engineeringPaul Michael COUTO (1), Daniel Francois MALAN (2)1: Cartledge Mining and Geotechnics, Australia; 2: University of Pretoria, South AfricaNumerical modelling of pillars with weak alteration layers using the TEXAN code1126 At Everest Platinum Mine, pillar failure occurred in 2008 owing to a weak alteration layer in the pillars. A numerical back analysis was conducted to ascertain design parameters for the ground conditions. The displacement discontinuity code, TEXAN, proved to be useful to simulate the pillar failure. The capability of the code to simulate irregularly-shaped pillars on a large scale was indispensable for this analysis. Furthermore, the built-in limit equilibrium model allows the pillar spalling and failure to be simulated. The model contains a parting at the hangingwall and footwall contacts which appears to be attractive to simulate the effect of the alteration layer. The model was calibrated using data, observations and other information from Everest Platinum Mine. This calibrated model allowed for the study of possible layouts when similar ground conditions are encountered in future. | Pillar design, pillar strength, weak alteration layer, limit equilibrium model, displacement discontinuity numerical modelling
T15: Rock and rock mass propertiesDavide ELMOUniversity of British Columbia, CanadaThe Bologna interpretation of rock bridges: what is real and what has the potential to be real?1127 This paper presents a provocative discussion on the subject of rock bridges and, by extension, on the topic of rock mass strength. We believe that there cannot be innovation in rock engineering if we are not open to looking at problems from a different perspective, even though that means abandoning practices that are considered industry standards for better or worse. The Bologna Interpretation of rock bridges states that one can only know where a rock bridge is once one measures it. And to measure it, you need the rock mass to fail. This interpretation highlights the indeterministic nature of rock bridges: they become real only when we look at them. Before failure, there are no actual rock bridges, only potential rock bridges which exist everywhere at once. | Rock Bridges, Bologna Interpretation, Rock Mass Strength
T03: Deep geothermal energyMarlene VILLENEUVE (1), Ben KENNEDY (2), Anette MORTENSEN (3), Elodie SAUBIN (2), Aliaa HAMMOUD (1)1: Montanuniversität Leoben, Leoben, Austria; 2: University of Canterbury, Christchurch, New Zealand; 3: Landsvirkjun, Reykjavik, IcelandInforming deep geothermal reservoir rock mass properties from drilling data - experience from Krafla, Iceland1128 During geothermal drilling it is important to know the quality of the rock mass for well completion, mud weight selection, interpreting features of interest, to characterise the subsurface in the absence of core. In deep geothermal drilling, tens to hundreds of meters are drilled without cutting retrieval and, therefore, without insight into the rock mass. Wireline logs are commonly used to interpret the subsurface, however, these data are typically collected after drilling an interval. Despite their increasing development, studies using drilling parameters and logging-while-drilling to interpret the rock mass in high-temperature, deep geothermal environments remain rare. In this paper we present a method where the drilling parameters from previous drilling at Krafla are used to assess the quality of the rock mass, with particular focus on its effect on drillability. This demonstrates how methods from geotechnical drilling and tunnelling can inform geothermal drilling. | Supercritical fluid, drilling performance, ROP, WOB, fractures
T05: Digitalization & AutomatisationDavid HACKER (1), Martin ZEINDL (2)1: Dipl.-Ing. Bernd Gebauer Ingenieur GmbH, Germany; 2: Landesbaudirektion Bayern, GermanyProject management in connection with a digital construction site with BIM in tunneling1129 The special features of tunneling create great potential for utilizing the advantages of the digital construction site and the BIM method during construction. The approach was applied to the execution of an approximately 600 m long road tunnel for mining excavation. Data sources, such as the digital tunneling documentation, were combined in a central live data management system and used efficiently, especially for project controlling and risk management. In addition to an As-planned model, an As-Built model was created during construction implementation on the basis of the digital construction site data. Each volume based calculation of time (4D) and costs (5D) conducted for the project was in accordance with the construction contract guidelines and specifications. These calculations formed the basis for checking monthly invoicing, performing precise target/actual comparisons and transparently presenting forecasts. | Digital Construction Site, BIM, Tunneling, Project Controlling, Monitoring Dashboard, Data Management
T04: Deep mining and tunnellingAlexey SHARIPOV, Amoussou ADOKOSchool of Mining and Geosciences, Nazarbayev University, KazakhstanAn investigation of the effect of rock brittleness on rockburst prediction in seismically active mines1130 The aim of this paper is to investigate the effect of the brittleness indices (B1 and B2) on the rockburst damage potential classification performance using Artificial Neural Network classifiers. Rockburst incident cases from seismically active mines are used to implement the proposed ANN models. Several scenarios were considered. The performance of the models was evaluated and the results indicated that the brittleness index has a great influence on the predictive performance of the models, especially for severe rockburst cases. The classification rates vary between 60-88% depending on the scenarios. Overall, showed a slight higher impact on the model accuracies compared to. The classification results showed some superiority over existing studies. It is concluded the results of the present study can be useful in managing ground prone to rockburst. | Rockburst potential damage, rock brittleness, ANN classifiers, rockburst intensity, mine seismicity
T13: Numerical methods in rock engineeringSimon Heru PRASSETYO (1), Ganda Marihot SIMANGUNSONG (2), Yofi OKATRISZA (3), Imam SUBCHI (4)1: Mining Engineering, Institut Teknologi Bandung, Bandung, Indonesia; 2: Mining Engineering, Institut Teknologi Bandung, Bandung, Indonesia; 3: Commitment-Making Officer for Cirebon-Kroya Double-Track Railways, Directorate General of Railways, Ministry of Transportation of the Republic of Indonesia, Jakarta, Indonesia; 4: Project Manager for the Kebasen Tunnel Construction, PT. Adhi Karya (Persero) Tbk, Jakarta, IndonesiaNumerical modeling and monitoring of blast-induced ground vibration of the Kebasen railway tunnel in Indonesia1131 This paper presents the findings of numerical analysis and monitoring of blast-induced ground vibration of a rock tunnel for the Kebasen railway tunnel in Indonesia. The numerical analysis uses the blast load approach that calculates the magnitude of the equivalent blast load to be imposed on the excavation boundary according to the blasting sequence. This dynamic simulation is conducted using 2-D numerical software called FLAC. The results of the numerical simulation are consistent with the PPV and ground vibration curve from the field monitoring and provide site-specific PPV equations for the Kebasen tunnel. This paper suggests that a safe blasting design can be produced based on preliminary numerical analysis, particularly when site-specific blast-induced ground vibration data are not readily available. | Rock tunnel, blast load, blast-induced ground vibration, peak particle velocity, numerical model, Kebasen railway tunnel
T06: Geological investigation and characterizationAletta Gertruida HARTZENBERG (1), Daniel Francois MALAN (2)1: SRK Consulting, Canada; 2: University of Pretoria, South AfricaStructural mechanisms contributing to large-scale hangingwall instabilities on the UG2 reef horizon1133 The platinum mines in the Bushveld Complex of South Africa are characterized by a structurally complex rock mass. The mining activities in the narrow hard rock reefs are labour intensive with manual drilling, blasting, and cleaning methods. The underground personnel operate near the mining face where there is an increased risk of falls of ground. The presence of geologic structures in the stopes contributes towards hangingwall and pillar instabilities. The resulting falls of ground and large collapses may result in fatalities, significant ore reserve write-offs and even mine closure. Weak clay-like (alteration) zones contribute to these instabilities but are typically overlooked by mining personnel as it is not commonly encountered, and it is therefore not identified as a hazard. This paper summarizes the findings from case studies that investigated the impact of these structures, as well as suitable remedial strategies that may significantly reduce the risk of instabilities and improve mining safety at these operations. | structural complexity, hangingwall instability, pillar instability, ground penetrating radar
T13: Numerical methods in rock engineeringRichard WITASSE (1), Jean-Francois BRUCHON (2), Sebastien BURLON (2)1: Seequent, The Netherlands; 2: Terrasol, FranceConsideration of Creep Deformation in Deep Underground Gallery Excavation in Claystone1134 This article deals with the numerical analysis of long-term behaviour of deep underground tunnel structures in claystone with “ductile lining” using PLAXIS 2D. The constructed gallery is a 2.6 m radius circular made of yielding sprayed concrete lining and is constructed at a depth of 500 m in a uniform claystone mass subjected to creep deformations. A visco-elastoplastic model has been used for describing the mechanical behaviour of the claystone. To prevent the development of excessive axial forces in the lining, yielding elements within the sprayed concrete lining have been used. They are modelled using a user-defined material model and special attention is dedicated in this article to the numerical formulation of such constitutive modelling. This article will finally present the short-term and long-term closure evolution results obtained in this context and highlight the good agreement between experimental measurements and numerical predictions, indicating the accuracy of the implemented creep law. | PLAXIS 2D, creep model, tunnel, rock
T13: Numerical methods in rock engineeringSebastien BURLON (1), Jean-Francois BRUCHON (1), Richard WITASSE (2)1: Terrasol, France; 2: Seequent, The NetherlandsA Model Benchmark Exercise for the 2D Analysis of a Tunnel Excavation in Rock1135 The Hoek-Brown with softening model (HBS model) has been recently added to the PLAXIS material library. This was a good opportunity to experiment the PLAXIS software capabilities for underground excavation in rock where usually FLAC is often being used. An example related to a 2D excavation analysis of a tunnel in a rock mass is presented. Extensive elements of comparison are proposed with an identical analysis run in both PLAXIS 2D and FLAC 2D to analyse the possible differences due to the implementation specificities. Results obtained will be presented in terms of tunnel convergence, structural forces in shotcrete and axial forces in rock bolts for which very good agreement between both solutions is observed. | Rock, FLAC, PLAXIS 2D, tunnel, finite element
T07: Geological risks and natural hazardsÖmer AYDAN (1), Yuki MURAYAMA (2), Takashi ITO (1), Naohiko TOKASHIKI (1)1: University of the Ryukyus, Okinawa, Japan; 2: Chuden Engineering ConsultantsThe assessment of dynamic stability of rock slopes with hexagonal jointing through shaking table tests and dynamic limiting equilibrium method (DLEM)1137 The authors investigated the dynamic stability of rock slope consisting of hexagonal blocks through model tests on shaking table and evaluate their stability through dynamic limiting equilibrium method (DLEM). Experiments indicated that the failures may be toppling or sliding and, they may be of active or passive modes. Critical acceleration levels can be estimated from the limit equilibrium method if frictional properties of rock blocks and the geometry of model slopes together with appropriate consideration of failure modes. | Hexagonal jointing, dynamic limiting equilibrium method, dynamic, static, shaking table, slope
T12: New developments in rock supportIryna KOVALEVSKA, Volodymyr BONDARENKO, Hennadii SYMANOVYCH, Ivan SHEKA, Yevhenii TSIVKADnipro University of Technology, UkraineModeling the rational parameters for innovative fastening systems in mine workings using composite materials1138 The leading methodologies (mathematical modeling and computational experiment) for studying geomechanical models to represent the state of systems "rock mass - reinforced rocks - innovative support system" in complex mining and geological conditions are considered. Mathematical modeling of carbon fiber-reinforced plastic arch support (CFRP) was carried out. A comparative analysis of the stress and strain state of the system "rock mass - support made of composite materials" with the stress and strain state of the existing roof support system in the mine was carried out. A laboratory simulation was carried out to determine the carrying capacity of the new shoring structure by creating a model on a 3D-printer in accordance with the basic principles of geometric similarity theory. The reliability of the calculations carried out and the results obtained has been substantiated by comparing the data of the computational experiment and the laboratory simulation. | carbon fiber-reinforced plastic, mine workings, composite material, support, stress-strain state, physical and mechanical properties
T04: Deep mining and tunnellingKamilya OMIRZHANKYZY, Ali MORTAZAVISchool of Mining & Geosciences, Nazarbayev University, Astana, KazakhstanA numerically based geomechanics risk assessment of the cut and fill underground mining method1139 The study of rock pillar stability is a common concern in mining engineering. It is critical to enhance predictive research of the mining effect and improve design to avoid catastrophic failures in mines operating at great depths. This results in the creation of pillars that must be retrieved during subsequent phases of excavation, typically under conditions of extreme stress. The purpose of this work is to examine the geomechanical parameters affecting pillar stability and behavior under the complicated nature of the rock mass in-situ, boundary conditions, and operational complexities associated with the cut-and-fill mining method at great depths. To evaluate the pillar deformation mechanisms, a comprehensive Finite Element Analysis was conducted. The obtained results are discussed and presented in terms of pillar stress and displacement fields. A parametric analysis was conducted to compare and determine the significance of geomechanical design parameters on pillar behavior, stability, and bursting potential. | Geomechanics Design, Pillar Stability, Risk Assessment, Cut and Fill method
T13: Numerical methods in rock engineeringYingcai HOU (1), Lushan SHU (1), Kai SHEN (2), Yadong XUE (1)1: Department of Geotechnical Engineering College of Civil Engineering, Tongji University, People's Republic of China; 2: School of Civil Engineering, Central South University, Changsha, ChinaThe shear behavior of the rock-concrete interface with different angles: A DEM simulation1140 During the whole life of a tunnel lining, the concrete-rock interface is one of the weak areas. To study the shear strength of concrete-surrounding rock interfaces, a direct shear test with a flat interface was carried out. The mechanical properties of contact surfaces with different sawtooth parameters were simulated via MatDEM based on the discrete element method. The four tooth angles (0°, 15°, 30°, and 45°) and eleven normal stresses (0.5~1.5MPa every other) were simulated. The results show that the shear strength increases with increasing normal stress for all four sawtooth angles. As the sawtooth angle increases, the shear strength increases due to the increasing cohesion and contact area. When the sawtooth angle is 15°, the failure occurs mainly along the interface. The fractures develop from the interface and the sawtooth is cut off when the angle is greater (30°and 45°) due to the mechanical occlusion. | Concrete-rock interface, Shear behavior, Sawtooth angle, Direct shear test, MatDEM
T13: Numerical methods in rock engineeringJan Abram MARITZ, Daniel Francois MALANUniversity of Pretoria, South AfricaA numerical modelling study of the effect of pillar shape on pillar strength1141 Bord and pillar layouts are typically designed using square or rectangular pillars. Pillar cutting is poor in many hard rock mines and many pillars have an irregular shape. This may affect pillar strength. The “perimeter rule” is commonly used for rectangular pillars to determine an “effective width”, but its applicability to pillars with irregular shapes has never been tested. This paper describes numerical modelling to investigate the effect of pillar shape on pillar strength. A limit equilibrium model, implemented in a displacement discontinuity code, was a valuable approach explored in this study. Preliminary evidence indicates that the perimeter rule should not be used for irregularly-shaped pillars. For rectangular pillars of increasing length, the numerical model correctly predicts an increase in pillar strength for an increasing in length. However, the increase in strength predicted by the modelling is higher than that predicted by the perimeter rule. | Pillar strength, Perimeter rule, Limit equilibrium model, Irregular pillar shape
T01: Challenging rock engineering projectsJoachim MICHAEL (1), Lisa WILFING (2)1: Prof. Quick und Kollegen - Ingenieure und Geologen GmbH, Germany; 2: Boley Geotechnik GmbH, GermanyComplex tasks to evaluate the feasibility of two railway tunnel variants in terms of tunnel construction1142 The expansion/new construction of the railway line "Hanau-Würzburg/Fulda-Erfurt" is one of 13 infrastructural projects of the Deutsche Bahn AG that are to be implemented with high political priority. The new DB-Line Gelnhausen-Fulda is a sub-project of this infrastructure project with a section of approximately 42 km (variant IV) respectively 48 km (variant VII) and hence, the planned construction of up to 80 percent of each variant in a tunnel. From a geotechnical point of view, two route variants are examined in detail regarding feasibility of the tunnel construction and taking hydrogeological and natural aspects into account. Both variants have a very high impact and require very different requirements on the planning and selection of suitable tunneling methods. In this article the relevant geotechnical, geophysical and rock-mechanical investigations and findings are presented in detail as the basis of the decision-making process in finding the most economical and operational suitable route variant. | Tunnel, Geotechnical Investigation, complex ground conditions, Building information modeling
T18: Early Career Forum (Young Researchers)Michael ALBER (1), Leandro ALEJANO (2), Tobias BACKERS (3)1: Alber GeoMechanics / Ruhr University Bochum, Germany; 2: University of Vigo, Spain; 3: Ruhr University Bochum, GermanyHow to form competent rock engineers1143 The profession of a rock engineer is not defined in any academic curriculum. We discuss the professional requirements for civil engineering or mining engineering applications and recommend the necessary classes to form a competent rock engineer. Emphasis is placed on the knowledge about the creation of the appropriate geological and geotechnical model through abstraction of results from site investigation and rock mechanical principles. Design analysis and constructability are further important parts in rock engineering education. The key challenge is, however, to recruit students into entering this rewarding professional career and to provide proper education to them. As most universities tend to hire basic scientists there is little conveyance of personal experience from rock engineering practitioners and little appreciation for rock engineering works. | Rock Engineering, Education, Professional requirements, Career satisfaction
T07: Geological risks and natural hazardsDinesh JAGANIYA, Manish SHAH, Usha PATELDept. of Applied Mechanics, L D College of EngineeringEvaluation of natural foliation effect on deformation characteristic and shear strength parameters of Chamoli (Uttarakhand) rock using a Triaxial system1144 In major part of the Chamoli, high degree of metamorphic rock are identified. The objective of this research paper is to examine the effect of natural foliation of Chamoli rock on shear characteristics and failure patterns through different anisotropic angles using an automated triaxial system. In present study, seven anisotropic angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) were simulated on a cylindrical specimen of diameter 50mm and length of 100mm based on the natural foliation of rock. From the experimental results and analysis based on Mohr-Coulomb and modified Hoek-Brown criteria, it is observed that the strength of rock decreased from 0° to 30° and the rock strength is continuously increased from 30° to 90°. Simulation of failure patterns in tested specimens are matched to anisotropy planes from 0° to 30°. As per above conclusion the natural foliation (anisotropic) behaviour is catastrophically affected on a strength and failure modes of Chamoli rock. | Anisotropic rocks, Natural foliation, Chamoli rock, metamorphic rocks, Modulus anisotropy, Triaxial system
T03: Deep geothermal energyKohei TAKUMA (1), Yuto WATANABE (1), Kiyotoshi SAKAGUCHI (1), Kazumi OSATO (2), Amane TERAI (3), Noriaki WATANABE (1)1: Tohoku University, Japan; 2: Geothermal Energy Research and Development Co., Ltd. (GERD), Japan; 3: Japan Organization for Metals and Energy Security (JOGMEC), Tokyo, JapanCarbon dioxide (CO2) fracturing of volcanic rocks under geothermal conditions1146 An enhanced geothermal system that uses carbon dioxide (CO2) for both reservoir creation and thermal energy extraction has been attracting attention in Japan. For this system, CO2 fracturing is conducted to create highly permeable fractures in low-permeability reservoirs, for instance, consisting of volcanic rocks. However, there is no previous study on CO2 fracturing of volcanic rocks under geothermal conditions, and possibility and characteristics of such fracturing are therefore unknown. Here we present results of CO2 fracturing experiments on andesite and basalt at 250 °C and a confining pressure of 30 MPa. It is demonstrated that CO2 fracturing occurs at a lower pressure than water fracturing and produces a more complex fracture pattern with a substantial permeability improvement. Additionally, it is shown that CO2 fracturing with water, in which CO2 is chased and pressurized by water, can produce larger-aperture fractures (i.e., larger permeability improvement) with keeping the advantage in CO2 fracturing. | carbon dioxide, fracturing, volcanic rock, enhanced geothermal system, breakdown pressure, fracture pattern
T12: New developments in rock supportYasuhiro YOKOTA (1,2), Kensuke DATE (1,2), Atsushi SAINOKI (3), Masako ISHII (2,4), Kazuhiko MASUMOTO (2,4), Mori UTSUNO (2)1: KAJIMA Technical Research Institute Singapore, Singapore; 2: KAJIMA Corporation, Japan; 3: Kumamoto University; 4: Kajima Technical Research Institute, JapanReinforcement effect of deformation-controlled tunnelling supports based on three-dimensional tunnel excavation analysis1147 In recent years, many tunnel excavation projects are planned despite swelling ground conditions and/or great depths subjected to high ground pressure around the world. In such cases, there is a risk that the high ground pressure will exceed the loading capacity of the conventional rigid supports, leading to brittle failure. Accordingly, the authors have been developing new deformation-controlled supports that can reduce stress acting on steel supports, shotcrete, and rock bolts by gradually resisting high ground pressure while controlling tunnel deformation. Here, we report on a study of support specifications suitable for actual tunnel excavation, performed by developing the constitutive model of deformation-controlled supports and analyzing 3D tunnel excavation. | Tunnel, simulation, deformation-controlled support, steel support, shotcrete, rock bolt
T13: Numerical methods in rock engineeringMeng WANG, Zhan YU, Jianfu SHAOUniversity of Lille, CNRS, FranceNumerical modeling of cracking process in partially saturated porous media and application to rainfall-induced slope instability analysis1148 Rainfall-induced landslides are one of the major natural catastrophes causing heavy economic and human loses. In this study, a new numerical model is proposed by considering crack initiation and propagation and hydromechanical coupling. For the description of cracking process, a new phase-field model is developed for porous media with hydromechanical coupling process. In particular, a new evolution law is proposed by considering both tensile and shear cracks as well as mixed-mode. The effects of pore pressure and capillary pressure on cracking evolution are further taken into account. Moreover, the intrinsic permeability of rock is also modified by the induced cracks. The proposed model is implemented in the framework of finite element method. It is applied to the analysis of rainfall-induced landslides. An example based on real case is considered. Progressive deformation and cracking process is investigated and analyzed. | Cracking, Porous rocks, Phase-field method, Hydromechanical coupling, Rainfall-induced landslides
T03: Deep geothermal energyWeiren LIN (1), Osamu TADAI (2)1: Kyoto University, Japan; 2: Marin Works Japan LTD, JapanRelationship between thermal conductivity and porosity in sedimentary soft rocks by an experimental approach1149 Relationship between thermal conductivity and porosity in sedimentary rocks are required for understanding the fundamental characteristics of rock thermal property in geoscience and geoengineering areas. To examine the relationship by laboratory experiments, we used core samples collected from a deep ocean drilling program called Nankai Trough Seismogenic Zone Experiment by Integrated Ocean Drilling Program. The thermal conductivity of the core samples was measured at high pressure to simulate subduction by reducing the sample porosity. The experimental results revealed a clear inverse relationship between thermal conductivity and porosity of the sedimentary rocks. | Sedimentary soft rock, Thermal conductivity, Porosity, High pressure, Laboratory experiment
T15: Rock and rock mass propertiesXiwei ZHANG, Lei SHINortheastern University, Shenyang, ChinaDevelopment and functional verification of an ultra-deep drilling core geological environment true triaxial apparatus1150 Given that the drilled core diameter decreases with increasing depth and there is no true triaxial apparatus for testing the complete stress–strain behavior and long-term deformation behavior of small-sized cores, a geological environment true triaxial apparatus was developed. The apparatus was mainly designed to obtain the complete stress–strain curves of hard rock specimens measuring 25 mm×25 mm×50 mm, while also considering the measurement of long-term deformation. This device focuses on solving technical problems such as inaccurate measurement of specimen deformation, low stiffness of the apparatus, mutual interference between pressure chamber oil pressure and actuator pressure.The deformation behavior of Xiling ultra-deep drilling cores was measured using this apparatus. | ultra-deep drilling core; true triaxial test; complete stress–strain; time-dependent failure
T15: Rock and rock mass propertiesJian YANG (1,2), Li-Yun FU (1,2)1: Shandong Provincial Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China); 2: School of Geosciences, China University of Petroleum (East China)Temperature- and pressure-dependent dynamic and static elastic moduli1151 The differential characteristics of temperature- and pressure-dependent dynamic and static elastic properties are investigated in a range of temperature and confining pressure for porous sandstone. Results show that the dynamic and static Young’s moduli increase against confining pressure, whereas the dynamic one decreases and the static one increases against temperature, respectively. The ratios of static and dynamic elastic properties for the Young’s modulus decrease against the ratio of thermal stress to confining pressure. The opposite result is observed for the Poisson’s ratio. We demonstrate that the progressive crack closure of primary microcracks associated with the limited expansion of cement material is dominant in the range of experimental pressure and temperature, instead of the development of new microcracks during thermal treatments. Therefore, the axial and radial strains decrease with increasing pressure and temperature, which reduces the static Poisson’s ratio but increases the static Young’s modulus. | Dynamic and static moduli, Temperature and pressure dependence, Microcracks, Strain amplitudes
T12: New developments in rock supportRoberto LUIS (1), Rico BRÄNDLE (1), Gabriel VON RICKENBACH (1), German FISCHER (2), Sergio MARK (2)1: Geobrugg AG; 2: Geobrugg Andina SpARational design for tunnel ground support with membranes based on the geomechanically classification of Q by Barton1153 The parameters to consider for an optimal solution for the design of underground rock support are the lifetime of the tunnels, the use of the tunnels, the safety level, and the cost. One of these design systems was developed by Barton. Nevertheless, the system has some limitations when it comes to dynamic ground conditions or higher static loads. With new ground support high-tensile steel membranes, the focus shifts from the bolt only, to an underground rock retention system where the membrane plays a significant role. An optimal load transfer from rock mass to the support system, be it dynamic or static, can be reached by high tensile steel meshes, that allow a wider bolt spacing. The proposed extension of the Q System considers the severe conditions the mining industry faces to get the ore from increasingly deep stops. | Q System, rock support, ground conditions, ground support membranes, tunnel safety, high tensile steel membrane
T15: Rock and rock mass propertiesZhen YE (1), Qian LIU (2), Qiang XU (1), Xiujun DONG (1), Feng PU (1)1: State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, China; 2: Graz University of Technology, AustriaA practical approach to determining the basic friction angle of natural and rough discontinuities in carbonate rock slopes1154 This study investigates the suitability of an adapted portable shearing box to measure the shear-induced dilation of a discontinuity and how the basic friction angle can be reliably derived from the shear data with dilation. Results show that samples with significant roughness are required. The reliability of the resulting basic friction angle depends on both the magnitude of the applied normal loads and the horizontal base length used to calculate the angle of dilation. We have developed data processing techniques to identify the optimal horizontal base length. The proposed method was successfully applied to estimating the basic friction angle of discontinuities that control the blocks stability in Kaili carbonate slope. | Adapted portable shear box, horizontal base length, dilation angle, basic friction angle
T06: Geological investigation and characterizationScott KIEFFER, Qian LIUGraz University of Technology, AustriaBlock in Point Cloud Data (BLOCKinPCD): A digital characterization system for rock outcrops1155 The extraction of 3D block structure from a point cloud is a nontrivial but important task in rock engineering. Block in Point Cloud (BLOCKinPCD) is a novel processing system that converts the point cloud data of rock outcrops into 3D rock structure. The workflow and processing functions include: (1) spatially identifying and extracting the point clouds of each discontinuity set; (2) quantifying the geometric parameters of each set (orientation, spacing and persistence); (3) characterizing the in-situ block system by assembling the block-forming sets into discrete fracture network; (4) quantifying the volume distribution of the block system and (5) evaluating the stability of blocks intersecting the excavation surfaces. As shown herein, BLOCKinPCD has been successfully applied to outcrops exposed in rock slopes and tunnel excavations. | Remote measurement, point cloud, rock structure, block system
T15: Rock and rock mass propertiesHasan ARMAN, Safwan PARAMBANUnited Arab Emirates University, College of Science, Geosciences Department, Al Ain, United Arab EmiratesStudy on the relationship between uniaxial compressive strength and elastic properties of limestone with various sample diameter1157 Uniaxial compressive strength (UCS), elasticity modulus (E) and Poisson’s ratio (υ) are critical design parameters in engineering. This study investigates the relationship between the UCS, Et (slope of the line tangent at 50% of the UCS) and υ of limestone core with various diameters. Core samples with a diameter of 25, 38, 48, 54 and 63mm were prepared for the UCS tests with strain gauges. The results were analyzed using linear regression between UCS and Et and υ with different sample diameters. The regression analysis results show that the Et has weak to strong positive and negative correlations with the UCS for sample diameter. The correlation between the υ and UCS is variably weak to strong for sample diameters of 38, 63, 25, 48 and 54mm. In general, the mean Et and υ decrease with increasing sample diameter increments, however, no meaningful trends are found for the UCS case. | Uniaxial compressive strength, Modulus of elasticity, Poisson’s ratio, Limestone, Sample diameter
T15: Rock and rock mass propertiesRabin Kumar SAMAL, Gangavarapu Teresa DES DE MONA, Sunita MISHRADepartment of Mining Engineering, IIT Kharagpur, IndiaBehaviour of a pre-defined crack propagating under dynamic tensile loading condition1158 Crack propagating at the rock-tool interface is of paramount importance while designing an excavation process. The present study aims to analyze the behavior of a crack propagating in brittle material like sandstone rock in comparison to ductile material like Aluminum alloy. A three-dimensional finite element model of split Hopkinson pressure bar setup was developed with a pre-cracked dog bone-shaped specimen to understand the behavior of crack using two non-linear strain rate dependent constitutive models, i.e., the Johnson-Cook model and Drucker Prager model. The numerical results were first validated with the experimental ones and then the effect of the crack parallel to the loading direction was studied under dynamic tensile loading conditions. The results show that the peak stress values are more at the center and tip of the crack for aluminum alloy than for the intact aluminum alloy specimens. However, it is completely opposite for sandstone rock. | Brittle material, dynamic loading, FE model, pre-crack, SHPB, tensile loading
T15: Rock and rock mass propertiesAbhishek MOHAPATRA, Anjali KUMARI, Sunita MISHRADepartment of Mining Engineering, IIT Kharagpur, IndiaNumerical Analysis of Thermo-Mechanical Characterization of Indian Sandstone under Dynamic Compressive Loading Condition1161 It is quite impractical to ascertain the in-situ mechanical behavior of rocks subjected to high temperature and high confining pressure under dynamic loading conditions. Hence, the present study aims to numerically determine the thermo-mechanical properties of Kota sandstone rock under dynamic compressive loading conditions using a split Hopkinson pressure bar (SHPB) device. Thereafter, a numerical model is developed similar to the experimental setup used for the dynamic characterization of Kota sandstone using a commercially available finite element (FE) software package, ABAQUS. The specimen size of Kota sandstone was modeled with a 54 mm diameter and 0.5 slenderness ratio as taken by Mishra et al. (2019). A thermally sensitive strain rate-dependent constitutive model is adopted to validate the numerical parameters with experimental results tested at room temperature. The effect of the temperature and loading rate on the mechanical behavior of the Kota sandstone rock is studied numerically and stated herein. | Dynamic Loading, Finite Element, SHPB, Strain Rate Dependent, Temperature, Drucker-Prager
T15: Rock and rock mass propertiesMeng-Chia WENG (1), Hoang-Khanh LE (1), Hung-Hui LI (2), Chih-Shan LEE (1), Chia-Chi CHIU (3)1: National Yang Ming Chiao Tung University; 2: National Defense University; 3: National Taipei University of TechnologyInfluence of microscopic composition on the strength of rock-like materials under various loading rates1162 This study investigated the dynamic strength and failure mode of rock-like materials considering the effect of microscopic composition and loading rate. A series of uniaxial compressive tests and SHPB tests were conducted on specimens, which contained 40% and 60% grain contents by volume and two types of cementation material (gypsum and weak gypsum). The results indicate a lower grain content and, correspondingly, a higher matrix volume, yields a higher quasi-static strength. The dynamic strength is related to not only the grain content but also the degree of grain breakage. Moreover, inter-granular fractures mainly occur under quasi-static compressive conditions, and the failure mode becomes trans-granular when the strain rate is high. Specimens with lower grain content exhibited fewer fractures and larger fragments than those with higher grain content. Considering the influence of matrix property, the weak-gypsum-cemented specimens exhibited higher dynamic increase factor and lower strength than the gypsum-cemented specimens. | Rock-like material, spilt-Hopkinson pressure bar (SHPB) test, dynamic strength, strain rate
T13: Numerical methods in rock engineeringAlec TRISTANI, Lina-María GUAYACÁN-CARRILLO, Jean SULEM, Sebastián Ariel DONZISEcole des Ponts ParisTech, FranceApplicability of Artificial Neural Networks (ANN) for equilibrium state prediction in tunnel excavation1163 Simplified 2D analysis of ground support interaction using the convergence-confinement method, although useful in preliminary stages of tunnel design, may be inadequate for complex situations which necessitate 3D numerical simulations with high computational efforts and costs. An alternative approach based on machine learning is proposed here in order to evaluate the stresses and displacements at equilibrium in the lining of a supported tunnel. Based on data previously obtained by numerical simulations, the Bagging Method applied to Artificial Neural Networks (ANNs) is used. We consider a circular tunnel excavated in a Mohr-Coulomb elastoplastic medium. The analysis accounts for a large range of ground conditions, support characteristics, lay distances and tunnel radius. The results show that ANNs models perform well with the small dataset used here and can be considered as a useful alternative to complex 3D numerical simulations. | Deep tunnels, Machine learning, Numerical simulations, Bagging, Surrogate models
T03: Deep geothermal energyHeng ZHENG (1), Ersi XU (2), Jie LI (3), Jin CHEN (3)1: Yangtze University, People's Republic of China; 2: Engineering technology research institute of Southwest Oilfield company; 3: Engineering technology research institute of Xinjiang Oilfield companyStudy on the fracture propagation in geothermal during the hydraulic fracturing based on a coupled thermal-hydraulic-mechanical modeling1165 In this paper, a coupled thermal-hydraulic-mechanical modeling was proposed based on the linear elastic fracture mechanics to understand the effect of thermal stress field on fracture propagation. Due to a cooling zone was formed in the matrix when the fracturing fluid injection, the rock had a shrink dramatically when the temperature reached the threshold value. The simulations indicated that when the temperature increased to 180℃ from 155℃, the breakdown pressure and extension pressure decreased by 14.56% and 13.27%, and the total fracture length of multiple fractures propagation increased by 28.51%, which demonstrated that increasing the temperature difference can not only decrease the breakdown pressure and extension pressure, but also can offset the stress shadow caused in multiple fractures extension. This research was helpful for the hydraulic fracturing design when the horizontal well with multiple stage fracturing was adopted in the development of geothermal systems. | thermal stress, hydraulic fracturing, thermal-hydraulic-mechanical, thermo-elastic deformation, volume shrinkage
T03: Deep geothermal energyYujie ZHU (1,3), Chen XU (2,3), Yingguo HU (1), Xiaoli LIU (3), Enzhi WANG (3)1: Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water, Changjiang River Scientific Research Institute, Wuhan, China; 2: Changjiang Institute of Survey Planning Design and Research, Wuhan, China; 3: Tsinghua University, Beijing, ChinaInfluence of stress state based on hydraulic-mechanical coupling and water loading path on fault activity1166 In the exploitation of shale gas and enhanced geothermal energy, reservoir water storage and carbon dioxide storage projects, induced earthquakes are closely related to the activity of primary faults. A fractured cylinder sample with 60° inclination is adopted in the indoor test.The shearing test is used to explore the impact of different stress critical conditions and pore water pressure loading paths on the triggering mechanism and mechanical behavior of fault activity, providing reference for the reservoir impounding plan. The test shows that when the increased pore water pressure is the same, the higher the critical pressure, the greater the displacement of fault sliding and the more energy released. Pore pressure under different path loading has influence on the process of fault dislocation, but has less effect on the displacement of the fault. The stress state and pore water pressure determine the fault displacement. | Stress state, HM coupling, loading path, induced seismicity
T13: Numerical methods in rock engineeringTimo SAKSALATampere University, Tampere, FinlandNumerical prediction of thermal weakening effects on granite rock1167 This paper presents a numerical method to predict the temperature weakening effects on granite rock. Thermally induced cracking is modelled in the continuum sense by using a damage-viscoplasticity model based on the rounded Rankine surface. The governing thermo-mechanical problem is solved with an explicit staggered method. Rock heterogeneity is described as random clusters of finite elements assigned with the constituent mineral, here Quartz, Feldspar, and Biotite, material properties. The temperature dependence of the minerals is accounted for up to 800 C, i.e. well beyond the Curie point (573 C) of Quartz. The simulations demonstrate that the present approach can accurately predict the experimental weakening effects on the rock strength and stiffness as well as the macroscopic failure modes in tension. Moreover, it does so in a noncircular way, i.e. not using the laboratory data on rock strength as an input data in the constitutive description. | Thermal weakening, Rock strength, Granite, Thermo-mechanical problem
T15: Rock and rock mass propertiesDeepanshu SHIROLE (1), Gabriel WALTON (2), Ahmadreza HEDAYAT (3), Sankhaneel SINHA (4)1: Indian Institute of Technology Delhi, India; 2: Department of Geology and Geological Engineering, Colorado School of Mines, Golden, USA; 3: Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, USA; 4: Department of Geology and Geological Engineering, Colorado School of Mines, Golden, USAEvaluation of the dilatant behavior of a crystalline rock using full-field optical imaging and ultrasonic monitoring1170 Experimental study of rock specimens under uniaxial stress path has shown that ultimate failure in rocks occurs after the onset of crack coalescence associated with dilatancy. Typically, rock dilatancy is represented by estimation of averaged specimen-scale total volumetric strains (ε_v). However, in previous studies, full-field ε_v (i.e. variations throughout a specimen) has not been rigorously analyzed. Accordingly, in this work, the full-field deformation measurement method of 2D-DIC (digital image correlation) is implemented to characterize evolution of dilatative (ε_v<0) and contractive (ε_v>0) strains in Stanstead granite specimens under uniaxial loads. In-sync, ultrasonic monitoring was also conducted to non-destructively monitor damage in the specimen. Results showed that full field strains evolve in a heterogeneous manner, with some regions showing dilation, and some showing contraction. Also, increases in ultrasonic amplitude during the initial stages of testing were shown to be linked to the occurrence of contractant strains. | mage correlation, ultrasonic monitoring, dilatancy, contraction
T17: Rock slope engineeringArmin RODUNER, Helene LANTER, Manuel EICHERGeobrugg AG, SwitzerlandLatest developments to increase the quality of flexible rockfall protection barriers1171 To ensure that flexible rockfall barriers are able to effectively stop the dynamic impact of rockfall, several guidelines have been introduced worldwide since 2001. However, long-term experience shows that other, “natural”, load cases happen which are not covered by guidelines or certification tests. Proposed substitute scenarios, for these natural load cases, are now treated by means of 1:1 field tests to increase the quality of rockfall protection systems and to offer more safety through additional test procedures. At the same time, the more stringent requirements are intended to meet all the guidelines and practical instructions applicable in Europe. In this paper, the different guidelines are discussed, the load case scenarios and their requirements are described in detail and the adaptations to the rockfall protection systems are presented. | Rockfall, 1:1 field tests, Flexible protection barrier, Multiple Loading
T07: Geological risks and natural hazardsJeane Mokgadi MATSOBANE (1), Bryan Philip WATSON (2)1: Sibanye Stillwater, South Africa; 2: The University of the Witwatersrand, South AfricaAssessment of face area hangingwall stability in a hard rock bord and pillar mine1172 The aim of this project was to assist Triggered Action Response Plan teams to issue rapid yet comprehensive support recommendations in a production environment. The research was conducted in a shallow tabular hard-rock environment in a bord and pillar mining configuration. The assessment included evaluations of bord hangingwall behaviour under various geotechnical conditions, bord spans, face advances per blast, and the influence of the last line of permanent support. The results showed that the effectiveness of the last line of support is influenced by keyblock dimensions, particularly the perimeter exposure of these blocks in the hangingwall. A reduction in span and advance per blast were found to be beneficial in reducing the height of the potential falls of ground. A set of common failure conditions has been assessed and discontinuity orientations description is provided. The description of the condition is accompanied by recommendations of support configuration or suitable spans. | Face area, TARP, FOGs, Hangingwall, span
T06: Geological investigation and characterizationJorge TERRON-ALMENARA, Charlie C. LINorwegian University of Science and Technology (NTNU), Trondheim, NorwayPerformance of the empirical method with rock mass classification systems to derive optimal rock support design in poor rock mass conditions1173 The empirical method has been traditionally used for the design of permanent rock support in hard rock tunnels. Engineering classification systems have typically assisted empirical design with the description and classification of rock masses, together with recommendation of permanent rock support. In this sense, rock mass classifications have generally performed well, including poor ground conditions. However, research and studies during the last decades together with recent case records have shown that there is room for improvement when the empirical classifications are utilized in poor ground conditions. Some of the mentioned limitations are addressed in this article, through the study of a database with more than one hundred case records of monitored tunnels with empirical support design and excavated in poor ground conditions. The results indicate that a convenient design approach in poor ground conditions should involve the study of the ground behavior in the more traditional empirical method. | Empirical method, rock mass classification, poor ground conditions, rock support, ground behavior
T15: Rock and rock mass propertiesDanielle PAJIEP (1,2), Jian-Fu SHAO (2), Nathalie CONIL (1), Mountaka SOULEY (1), Philippe GOMBERT (1)1: National Institute for Industrial Environment and Risks; 2: University of LilleHydromechanical characterization of Château-Landon chalk behavior1176 The paper deals with the effect of water saturation degree on the stress–strain response of a high-porosity and pure chalk, the Chateau-Landon chalk. A general experimental methodology is presented, including hydrostatic and triaxial compression tests performed under drained conditions with loading paths combining variations of stresses and water saturation degree to characterize the hydromechanical behavior of this porous material. | Chalk, hydromechanical behavior, water saturation, porous
T09: Long term behaviour of underground structuresFrederico LARA (1), Lina-María GUAYACÁN-CARRILLO (1), Jean SULEM (1), Jana JABER (2), Jan CORNET (2), Gilles ARMAND (2)1: Laboratoire Navier/CERMES, Ecole des Ponts ParisTech, Université Gustave Eiffel, CNRS, Marne la Vallée, France; 2: ANDRA, Meuse/Haute-Marne Underground Research Laboratory, Bure, FranceInfluence of different support systems on drifts closure evolution in Callovo-Oxfordian claystone1177 At the Meuse/Haute-Marne Underground Research Laboratory several research programs have been dedicated to: (1) knowledge improvement of the Callovo-Oxfordian claystone response to the excavation; (2) development of the different disposal systems. In order to increase the understanding of the rock mass formation and support interaction, a drift composed of different support systems has been monitored for several years. As this one is oriented along the minor horizontal principal stress, the measurements exhibit an anisotropic closure of the cross section with the vertical convergence being higher than the horizontal one. It is thus of interest to evaluate the effect of flexible support composed of compressible wedges and of the final concrete lining on the closure evolution. Also, extensometers measurements and the stresses on the temporary support are analyzed in different zones of the drift. Finally, the results are compared to those obtained from other drifts excavated in similar conditions. | Convergence measurements, Tunnel excavation, Tunnel lining, Deep geological repository, Callovo-Oxfordian claystone
T13: Numerical methods in rock engineeringBenoît PARDOEN, Christos MOURLASUniversity of Lyon, ENTPE, LTDS, FranceMultiscale modelling of rock behaviour around underground works with an insight of microstructural characteristics influence1179 Rock behaviour conditions the stability of deep underground exploitations. The excavations generate deformations, damage, and fractures in the surrounding rock. At engineering scale, phenomenological constitutive models are often considered; however, macroscale behaviour takes its origin from small-scale properties. Their influence on material deformations and damage across scales remains complex. Therefore, the behaviour of a clay rock is modelled at two scales. The excavation and damaged zones around galleries are reproduced at large scale. The excavation-induced fractures are modelled with shear bands. The approach is enriched with microstructural characteristics of mineral inclusions and clay matrix. The material mesostructure and behaviour are embedded in a representative elementary volume. A double-scale numerical framework (FEM×FEM) with computational homogenisation relates small- and large-scale behaviours, as deformations and failures. The damage and cracking developments at micro/meso scales allow to predict macroscale shear banding. The results highlight the possibilities of double-scale computing to predict underground structure behaviour. | Damage, shear failure, double-scale modelling, microstructural characteristics, excavation
T13: Numerical methods in rock engineeringRuilin YANGOrica, United States of AmericaIntegral system of monitoring and modeling for blast optimization1180 Most mines seek fine fragmentation for down-stream operations to maximize mineral abstraction with minimized energy cost, e.g., mine-to-mill blast optimizations. On the other hand, maintaining stable highwalls and undisturbed nearby community is highly desirable. To obtain fine fragmentation, it is often required to design blasts with favorable energy concentration through explosive loading or blasthole delay timing. Blast designs have potential to increase blast vibration in general. To achieve the optimization, an integral system for accurate monitoring and reliable modeling of full blast design parameters for rock fragmentation and blast vibration is required. Current technology in the literature falls short for each of the needs. This paper presents an integral system, which includes the accelerometer-based blast vibration monitoring system, the multiple seed waveform blast vibration model, and the multiple blasthole fragmentation model. The three components together complete a close loop of the needs for blast optimization. | Near-Field Blast Vibration Monitoring, Near Field Blast Vibration Modelling, Full Blast Design Parameter Fragmentation Modelling
T08: Hydropower projects and damsYi LUO, Hangli GONG, Qiaoliang LI, Xinping LIWuhan University of Technology, People's Republic of ChinaStudy on dynamic response characteristics of cave-type excavation of high and steep dam abutment slope1182 The numerical simulation is carried out for the dynamic response characteristics of cave-type excavation at the left dam abutment of Zhongyu Hydropower Station. The results show that within the range of 20~100 m from the explosion source in the vertical direction, both the peak vibration velocity and the maximum principal stress of the particle present extremely obvious elevation amplification effect. Due to the influence of the ground stress and the excavation contour of the dam abutment, different layered blasting excavation and excavation unloading have different effects on the deformation and displacement of the surrounding rock of the dam abutment. In addition, during the excavation in a certain layer, the displacement change rate of the particles on the upstream and downstream sides of the dam abutment is usually first fast and then slow, and there will be obvious inflection points. | high and steep dam abutment slope, cave-type excavation, blasting vibration, dynamic response, elevation amplification effect
T15: Rock and rock mass propertiesLichun JIA, Qicong XU, Chongjun HUANG, Lei LI, Xiao WEI, Changhong ZHOUDrilling & Production Technology Research Institute, CNPC Chuanqing Drilling Engineering Company Limited, People's Republic of ChinaThe dynamic tensile strength and failure characteristics of transversely isotropic shale under impact Brazilian test1183 To comprehensively understand the failure behaviors under dynamic loading, a series of SHPB tests are conducted on deep Longmaxi shale under different loading rate at seven loading-bedding angles β. The results indicate that both static and dynamic BTS increase with the angle β. But the dynamic BTS are far greater than the static. However, as the loading rate increases, the anisotropic index decreases gradually. There is a positive correlation between dynamic BTS and loading rate, which is that the dynamic BTS increases with loading rate and the relation between dynamic BTS and loading rate is fitted by a power function with correlation coefficients R2 higher than 0.92. The failure results show that there are four typical fracture patterns, which are central tensile failure as β=0° and β=90°, bedding activation shear failure as β=15°, non-central arc fracture at β=30° and 45°, mixed mode fracture as β=60° and 75°, respectively. | Longmaxi shale, transversely isotropic, split Hopkinson pressure bar (SHPB), dynamic Brazilian tensile strength (BTS), failure patterns
T07: Geological risks and natural hazardsChia-Chi CHIU (1), Wen-Jie SHIU (2), Ching-Fang LEE (2), Meng-Chia WENG (3), Che-Ming YANG (4)1: National Taipei University of Technology, Taiwan; 2: Sinotech Engineering Consultants Inc., Taipei, Taiwan; 3: National Yang Ming Chiao Tung University, Hsinchu, Taiwan; 4: National United University, Miaoli, TaiwanSystem of highway slope disaster information collection, integration, simulation and judgement1185 Landslide and rockfall disasters frequently occur on road systems. Therefore, analyzing the disaster rapidly and deciding on the remediation method, is the key to reducing the loss. We have developed a ‘Highway slope disaster information collection, integration, simulation and judgment system’ which has three parts: (1) Geohazard rapid report system; (2) Multidisciplinary geological survey; and (3) Site-specific landslide simulation. This paper focuses on theYusui Stream debris flow and the disaster of the Minbaklu bridge as case studies to demonstrate the application of the aforementioned three components in disaster assessment. The key factor such as geological, terrain, distribution of weak plane, volume, process, and landslide mechanism, and finally provide a disaster report to concerned units for the assistance in follow-up decisions. | Slope, Disaster investigation, Information integration, Numerical simulation, Geological investigation
T12: New developments in rock supportBjarte GRINDHEIM (1), Charlie Chunlin LI (1), Are Håvard HØIEN (2)1: Norwegian University of Science and Technology (NTNU), Trondheim, Norway; 2: Norwegian Public Roads Administration (NPRA), Bergen, NorwayFull-Scale Pullout Tests of Rock Anchors in Limestone Testing the Interfacial Bond Strengths1186 Rock anchors are used to stabilise large scale infrastructures. The literature describes four failure modes of rock anchors: (1) steel tensile failure; (2) anchor-grout interface failure; (3) grout-rock interface failure; and (4) rock mass uplift. In this study full scale field tests of rock anchors were performed in a limestone quarry. These tests were designed to test failure mode 2 and 3 with bar anchors, with and without an endplate. The tests of failure mode 2 showed that the shear stress on the anchor-grout interface is highest at the proximal and attenuates towards the distal end at small loads and it becomes approximately uniform at 50% of the ultimate pullout load. The anchors designed to test failure mode 3 had an endplate, they showed that the shear stress on the grout-rock interface was highest at the distal end above the endplate and attenuated upward before slip starts on the interface. | Rock anchor, load transfer, shear stress distribution, bond shear strength, field tests
T04: Deep mining and tunnellingYuehan WANG, Guangyao SI, Joung OHSchool of Minerals and Energy Resources Engineering, University of New South Wales, Sydney, AustraliaCoupled Geomechanical CFD Modelling of Goaf under Goaf Gas Drainage: Impact of Goaf Characteristics1187 Australian mines heavily relied on a series of boreholes to control goaf gas emissions. The use of these boreholes not only reduces greenhouse gas but also recovers a large amount of energy. However, high suction pressure applied on boreholes may cause ventilation air migration from the working face to enter the goaf. The leaked air containing rich oxygen would react with the residual coal in the goaf and accumulate heat, which may cause spontaneous combustion and gas explosion risks. This paper developed a goaf CFD model to analyse the goaf gas distribution and leaked air flow pathways under the impact of intensive goaf gas drainage. Besides, the associated gas explosion risks will be quantified using Coward’s triangle based on the CFD modelling simulation results. Therefore, this CFD model can be used to optimise the drainage efficiency of intensive boreholes while ensuring mining safety during the operation period. | Goaf gas drainage, CFD modelling, goaf permeability, coal oxidation, gas explosion risk
T15: Rock and rock mass propertiesNeil BAR (1,2), Wulf SCHUBERT (1)1: Graz University of Technology, Austria; 2: Gecko Geotechnics LLC, Saint Vincent and the GrenadinesEvaluation of different methods for determining rock masses stiffness1188 Surface and underground excavations in rock are designed for ensuring stability. In many tunnel, underground cavern and rock slope projects, designing to acceptable deformation limits or tolerances is just as critical as stability. Understanding rock mass stiffness and deformability becomes an integral part of ground characterization and subsequent design. Deformation moduli for rock masses are often estimated using empirical methods that may have been developed from limited data, specific ground conditions, and provide a single result representing the behavior of an isotropic, homogeneous rock mass. However, most rock masses are heterogeneous or anisotropic, and deformation moduli can vary significantly depending on the loading direction. This paper reviews available empirical methods for evaluating deformation moduli and compares them with an observational model from monitored slope deformations in siltstones, sandstones and quartzite at a surface and underground mine in Australia. | Rock mass stiffness, empirical methods, deformation modulus
T15: Rock and rock mass propertiesPetar HRŽENJAK (1), Ivana DOBRILOVIĆ (1), Dražen NAVRATIL (2), Biljana KOVAČEVIĆ ZELIĆ (1)1: University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering, Croatia; 2: Croatian Geological Survey, CroatiaShear strength determination of very rough and partially filled extension fractures in thick-bedded and karstified limestones1189 Extension fractures that appear as very rough and irregular and with or without infill material, are common in thick-bedded and karstified limestones for which present-day methods for shear strength estimations are inappropriate. With the aim of determining the shear strength of such discontinuities, field research was carried out, in which large samples of blocks with discontinuities, as well as samples of filling material were prepared, on which then detailed laboratory tests were performed. Based on the obtained results, a modification of Barton’s JRC-JCS empirical model was made in such a way that the friction angle of the built-in filling material in the case of discontinuity with a filling was applied, instead of the residual friction angle. In addition, the joint contact coefficient (JCC) was introduced as the measure of the actual contact area between discontinuity walls by means of which the normal stress on the discontinuity surface can be corrected. | extension fractures, shear strength, friction angle, joint roughness coefficient, joint contact coefficient, Barton’s empirical model
T07: Geological risks and natural hazardsHaojie YANG (1), Gan QI (2), Jili FENG (1), Zhengyuan LIU (1), Dejian LI (1)1: China University of Mining and Technology Beijing, People's Republic of China; 2: China Institute of GeoEnvironment MonitoringFailure mechanism and slip characteristics of landslides on loess plateau by continuous-discontinuous method: A case study1191 This study focuses on the disaster-causing mechanism and sliding characteristics of sudden deep landslides in the loess area of Xiangning county of China. The continuous-discontinuous element method is employed to simulate the overall process of landslides from deformation accumulation to rupture and slip. The results show that the weak out-dip interlayer formed by long-term rainfall infiltration contributes to the landslides. The weak interlayer cannot provide sufficient anti-sliding force. Additionally, the soils at the leading edge exhibit a clear tendency of slipping at the beginning, and the mechanical process of landslide failure is shear-compression on the foot of the slope, shear in the middle, and pull crack at the trailing edge. During the sliding, the trailing edge sliding body obviously lags behind the leading edge sliding body. Finally, it is found that the numerical predictions are good in agreement with the field survey information of the loess landslides. | Landslides, Continuous-Discontinuous Method, Failure Mechanism, Slope Stability
T13: Numerical methods in rock engineeringChristian CANCINO (1), Loren LORIG (1), Augusto LUCARELLI (1), Kabo GABANAKGOSI (2), Otsile BAREI (2)1: Itasca Consulting Group, USA; 2: Debswana Diamond Company, BotswanaSlope support analysis at Jwaneng Mine1195 Jwaneng Mine is an open pit located in Botswana. The eastern wall is characterized by quartzitic shale bedding planes that dip moderately into the pit slope, hence, posing a risk of planar sliding once undercut. The Bench 17 area, located on the eastern wall, hosts one of the two major life of open pit mine switch-backs access to kimberlite. Previous failures in the interim design have reduced the switch-back width, adversely impacting effective haul truck movement. Mine operations developed a plan that optimized switch-back width by installing a 32 m high geogrid reinforced rockfill retaining wall. A study of additional foundation supports was recommended to meet the design acceptability criterion for this area. This paper describes a numerical assessment of the support design. | Slope stability, structural support, support design, numerical modeling
T17: Rock slope engineeringBattista TABONI (1), Gessica UMILI (1), Anna Maria FERRERO (1), Simone BLANC (2), Filippo BRUN (2), Stefano BRUZZESE (2), Luca M. ALBERTELLI (3), Iuri D. TAGLIAFERRI (3)1: University of Turin, Department of Earth Sciences; 2: University of Turin, Department of Agricultural, Forest and Food Sciences; 3: Land & CogeoThe influence of a heavy storm on a slope subject to rockfall phenomena: the Bazena case study1199 The evolution of rockfall phenomena depends on both rock mass and slope characteristics: variations in cover, morphology or vegetation induced by intense weather events can have huge consequences. Investigating these effects is required to assess the effectiveness of existing protection structures. This study focuses on the Bazena case (Brescia, Italy), a slope subject to rockfall phenomena, crossed by a provincial road connecting two valleys. Originally the slope was covered by a coniferous forest, which was almost completely destroyed by an extremely intense storm in 2018. In this context, the ASFORESEE model was applied to understand the value of the protection provided by the forest, over a period of 25 years. The output of ASFORESEE and other evaluations here proposed show that the forest played an active role in protecting the provincial road against rockfall phenomena. This work aims to highlight the potentiality of combining nature-based solutions and flexible barriers. | Rockfall, flexible barrier, nature-based solution, forest, ecosystem service, economic evaluation
T10: MonitoringJiayong TIAN (1), Kanghua ZHANG (2), Jiashu LOU (1)1: National Institute of Natural Hazards, MEMC, People's Republic of China; 2: Tianjin University, People's Republic of ChinaNext-generation high-resolution borehole tensor strainmeters for the measurement of six strain-components based on fully automated interferometric displacement sensors1200 Conventional borehole tensor strainmeters (BTSM) based on the measurement of inner-diameter changes of strainmeters by four capacitance gauges had been developed to measure three strain-components in the horizontal plane. The other three strain components are also important, but are difficult to implement because of large volume of sensors. In order to measure six strain-components completely, we develop a new high-resolution BTSM based on a fully automated interferometric displacement sensor with fibre-based heads of the millimeter dimension,which makes the gauge ultra-compact to implement the four inner-diameter-change measurement and other three-gauge measurements considering the influences of strain components in the plane of vertical normal. Compared with conventional BTSM, the impulse hammer test results show that gauge design of the new BTSM extends measurement resolution from 10-9 to 10-12 and increases the measurement bandwidth greatly, which advances the technology of borehole strain. | High-resolution borehole tensor strainmeters, Fully automated interferometric displacement sensors, six strain-components, Next-generation
T06: Geological investigation and characterizationYasmin Nicole BYRNE, Robert WHITTLECambridge Insitu, United KingdomThe impact of rock strength on the measurement of shear modulus from cavity expansion testing1201 The cavity expansion test is frequently used to determine the shear stiffness of rock. When stiffness is derived from an unload/reload event (cycle) then the process is repeatable and will give consistent values that are unaffected by drilling disturbance. The simplest interpretation of rock stiffness data is to assume the cycle is a linear-elastic event. In practice the response of the rock mass can be complicated by tensile failure and the level of shear stress. If the tensile strength is overcome and failure occurs, fracture growth can give cycles of reducing stiffness, unrepresentative of the rock mass at the insitu state. Material showing shear failure is likely to give a non-linear reduction of stiffness with strain. This includes decomposed and weathered materials. If the material remains largely intact, increasing the applied stress level will often produce a stiffer response with a power law trend. | Pressuremeters, Shear Stiffness, Tensile Failure, Cavity Expansion
T14: Petroleum engineering and carbon sequestrationLichun JIA, Hu DENG, Dianchen LIU, Zhilin LI, Weicheng LIDrilling & Production Technology Research Institute, CNPC Chuanqing Drilling Engineering Company Limited, People's Republic of ChinaAnalysis of fracture initiation pressure of horizontal well in transversely isotropic shale reservoirs1203 This study aims at analyzing the fracture initiation pressure (FIP) of horizontal wellbore in anisotropic shale by considering elastic and strength anisotropy. The FIP is deduced as a function of the anisotropic elastic properties, in-situ stresses, anisotropic tensile strength as well as bedding dip. The results show that the increase of the anisotropy of Young’s modulus, Poisson′s ratio and horizontal in-situ stress induces a reduction of the FIP. While an increase of tensile strength ratio Tv/Th and bedding dip will increase the FIP. It is concluded that the influence of Eh/Ev on FIP is the highest, followed by σH/σh, and then Tv/Th, while the influence of Poisson's ratio is the lowest. For the effect of azimuth of horizontal well, the FIP increases first and then decreases when the horizontal borehole azimuth is far away from the direction of maximum horizontal stress. | shale, transversely isotropic, fracture initiation pressure, modulus anisotropy, Poisson′s ratio anisotropy, tensile strength anisotropy
T07: Geological risks and natural hazardsDaniele SPIZZICHINO (2), Paolo Maria GUARINO (2), Gabriele LEONI (2), Milena DILETTO (1), Edoardo LUSINI (1), Fabio PAGANO (3), Marida SALVATORI (3), Daniela BOLDINI (4)1: University of Bologna, Italy; 2: ISPRA, Geological Survey of Italy; 3: Parco Archeologico dei Campi Flegrei, Pozzuoli (Na), Italy; 4: Sapienza University of Rome, ItalyInstability phenomena affecting the cultural heritage cave of Antro della Sibilla (Cuma, Italy)1204 The present work aims at the analysis of localized instability phenomena affecting the archaeological site of the Sibilla Antro. The cave was excavated by Greek colonists in the formation of Neapolitan Yellow Tuff, a pyroclastic weak rock. This rock is naturally fractured and weakly stratified: for these reasons local instability phenomena occurred along the whole extent of the Antro, worsened by the deterioration of past remediation interventions by passive dowels in the 1980s. Based on a geomechanical field survey and a laboratory characterization of the rock material, a 2D numerical model of the most threatened section was implemented to assess the stress concentration points and the current stability conditions. A proposal is also made for possible low impact measures for safeguard and conservation purposes. | weak rock, cultural heritage, instability, numerical analysis, Sibilla
T15: Rock and rock mass propertiesYudhidya WICAKSANA (1), Suseno KRAMADIBRATA (2), Seokwon JEON (3)1: Institut Teknologi Bandung, Indonesia; 2: Bumi Resources Minerals, Indonesia; 3: Seoul National University, Republic of KoreaEstimation of cutting force considering intermediate dynamic rock strength using multiple linear regression1206 This paper estimates pick cutting force using multiple linear regression considering rock properties determined under intermediate dynamic loading. Existing theoretical and empirical works on rock cutting performance have focused on cutting parameters and static rock mechanical properties. Even though rock cutting is a dynamic event, prediction models that consider dynamic rock properties have not been explored. Earlier research has demonstrated that the cutting mechanism in rock operates under intermediate dynamic conditions in which the strength would improve compared to its static state. Multiple linear regression analyses were performed to estimate the mean and maximum cutting forces of unrelieved cutting tests. This study compared the performance of the suggested models to that of the models produced by Evans, Goktan, and Roxborough & Liu. Statistical analysis showed that the suggested models have a lesser mean squared error to the data population than the theoretical models. | Rock cutting, Cutting force, Pick cutter, Intermediate dynamic loading, Multiple linear regression
T04: Deep mining and tunnellingYuepeng SUN (1), Biao LI (2), Nuwen XU (1), Qi WANG (3), Bei JIANG (3)1: Sichuan University, Sichuan, China; 2: Southwest Petroleum University, Sichuan, China; 3: China University of Mining & Technology (Beijing), Beijing, ChinaStability analysis of surrounding rock mass in underground powerhouse based on octree and catastrophe theory1207 Based on the underground cavern engineering of the left bank of Shuangjiangkou hydropower station, Octree theory is used to define the indexes of the MS spatial aggregation degree and the deviation values of MS frequency and energy, establishes the relationship with surrounding rock mass instability from three aspects of "time, space and strength". The cusp catastrophe model of the MS spatial aggregation degree and the deviation values of MS frequency and energy is established to quantitatively describe the early warning state of surrounding rock mass instability of underground cavern. The results show that the multi-level tree structure and voxels generated based on Octree theory is higher goodness of MS point set in three-dimensional space. The cusp catastrophe model based on the MS spatial aggregation degree and the deviation values of MS frequency and energy can effectively identify the early warning interval and potential damage area of surrounding rock mass, The warning time zone and potential damage zone quantified by this method are highly consistent with the characteristics of MS precursors with high recognition and field investigation results, which fully proves the rationality and applicability of this method. The research results can provide basis and reference for the early warning of surrounding rock instability in the later excavation of underground powerhouse. | Underground caverns; MS monitoring; early warning; Octree theory; Catastrophe theory
T15: Rock and rock mass propertiesSakshi ROHILLA, Resmi SEBASTIANIndian Institute of Technology Ropar, IndiaStudy of stress-dependent dynamic properties of jointed rock using resonant column apparatus1208 Field stress conditions have a significant impact on the mechanical characteristics of jointed rock masses. This paper investigates and discusses the effects of joint spacing and confining pressure on the dynamic properties of a jointed rock mass. The RCA was used to test jointed gypsum material at varied confining pressures and strain amplitudes. The normalised shear modulus and material damping ratio curves for various joint spacings and confining pressures have been produced. The modified hyperbolic and Ramberg-Osgood models were used to fit curves based on experimental data collected at various shear strain amplitudes and confining pressures. This study presents the best-fitted parameters showing the link amongst shear modulus and shear strain, in addition to damping ratio and shear strain for varied joint spacing. The eminence of confining pressure on shear modulus and damping ratio at various strain levels has been studied using the power function. | Jointed rock, Shear modulus, Damping ratio, Confining pressure, Joint spacing
T13: Numerical methods in rock engineeringGiuseppe CAMMARATA (1), Davide ELMO (2), Sandro BRASILE (3)1: Seequent, The Bentley Subsurface Company, Milan, Italy; 2: University of British Columbia, NBK Institute of Mining Engineering, Vancouver, Canada; 3: Seequent, The Bentley Subsurface Company, Delft, The NetherlandsModelling brittle rock mass behaviour in deep underground excavations1209 Thorough knowledge of brittle phenomena around underground excavations is of paramount importance for predicting the extension and shape of the failed zone and assisting in assessing adequate support and reinforcement systems. This behaviour is difficult to capture in conventional continuum modelling approaches, requiring the development of advanced constitutive models. A continuum constitutive approach based on the Hoek-Brown failure criterion and enhanced by introducing a softening rule to replicate the brittle behaviour of rock masses and associated failure due to dilatating sharing has been recently proposed. In this paper, this new Hoek-Brown with Softening model is adopted to predict the progressive brittle failure of the Lac du Bonnet granite at the Underground Research Laboratory Mine-by test tunnel. The results confirm the capability of the constitutive approach to replicate the brittle behaviour associated with strain localization. | Brittle rock failure, Continuum numerical models, Hoek-Brown with Softening, Mine-by test tunnel, Deep underground excavations
T06: Geological investigation and characterizationAbdelmadjid BENRABAH, Luis JORDA BORDEHORE, Salvador SENENT DOMINGUEZTechnical University of Madrid (Universidad Politécnica de Madrid), Madrid, SpainA review of the application of empirical methodologies for preliminary analysis of natural caves1210 Geomechanical classifications have been used for the analysis of tunnels and mines since the 1970's. The database generated is huge: all types of lithologies, countries and works. However, there are few studies on its application to caves. The geotechnical stability of natural and anthropic caves (troglodytes) is a very little studied subject and of vital importance from the point of view of safety: there are thousands of caves that can be visited in the world, as well as cave houses, cellars and underground hotels and restaurants. We propose a review of the application of empirical methodologies for analysis of natural and anthropic caves. Both rock mass classifications CGI and Q index are too conservative, even in some cases alarmist. Stable caves appear as transitional or even unstable in graphs (Q) and rock classes (CGI). | Cave Geomechanical Index (CGI), Scaled Span, Q index, Rock Mass Classification, troglodyte
T09: Long term behaviour of underground structuresMensan Dèlwindé Gildas Cedric AGBOLI, Dragan GRGIC, Albert GIRAUDUniversité de Lorraine, CNRS, Laboratoire GeoRessources, Nancy, FranceSelf-sealing experiments with water and gas injection on Callovo-Oxfordian claystone under X-ray tomography1211 Self-sealing tests with water injection were performed on artificially fractured core samples of the Callovo-Oxfordian claystone using an X-ray transparent triaxial cell. 3D X-ray scans and permeability measurements were performed continuously to assess the evolution of fracture volume and permeability. The impact of sample orientation (parallel and perpendicular to the bedding plane), calcite content and gas injection was analyzed. It resulted that the higher the calcite content, the less effective the self-sealing process. No significant influence of the sample orientation on the self-sealing process was identified. Self-sealing is generally fast at the beginning of the test and then stabilizes after one month. The initial permeability of the healthy claystone is partially restored, which is a promising result concerning the restoration of the initial sealing properties of the host rock. Injection of an inert gas has a delay effect on the self-sealing process due to the crack desaturation. | X-ray tomography, self-sealing, permeability, claystone, calcite content
T07: Geological risks and natural hazardsAline CONCHA-DIMAS (1), Ivan FABREGAT GONZALEZ (2)1: Institut Geològic de Catalunya. Presently: Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain; 2: Institut Cartogràfic i Geològic de Catalunya, Barcelona, SpainGeomechanical and hydrogeological characterization of fracture systems in Banyoles Karst caprock units, Catalunya1214 Banyoles karst systems, located in NE Catalonia, is tectonically controlled, and associated to an artesian aquifer. This karst system is formed at the surface by a cap layer of competitive marls and calcareous rocks above a highly dissolving thick unit of gypsum with depth larger than 20 m. The voids left by upward water flow of the artesian aquifer generates sinkholes at the surface. First, we analyzed aerial photographs to describe the latest karst activity from 1945 up to the present. Secondly, we performed eighteen scanline surveys to describe the cap-rock structure (Jv and RQD) and describe hydraulic aperture and transmissivity (ac, Tf) of each joint set. In the cap rock units, we found up to 7 fracture systems that define medium-large block size. Two fractures have the highest Tf values, order of magnitude between 10-1 and 10-3, critical for the generation of collapses where the gypsum unit is shallow. | hypogenic karst, cap-rock units, unitary block size, hydraulic aperture, transmissivity, Banyoles Lake
T04: Deep mining and tunnellingJörg-Martin HOHBERGIM/IUB Engineering AG, SwitzerlandPrediction of long-term deformation and dimensioning of support in squeezing rock under high overburden1219 Large infrastructure projects such as the railway base tunnels crossing the Alpine ridge are designed for a minimum service life of 100 years. The running tracks are adjustable to a few centimeters only and may be replaced after 50 years, but the tunnel lining must stay intact over the entire life span with secured clearance. The primary feature of such tunnels is their flat alignment for energy-efficient high-speed traffic of heavy trains, accepting long tunnel drives with high overburden of 1,500 m or more. Despite optimization of the horizontal alignment to avoid difficult rock conditions at best, the scarce geological reconnaissance leaves ample room for surprises such as faults, carst or squeezing rock. | Deep tunnels, squeezing rock, numerical methods, FEM, long-term behaviour
T05: Digitalization & AutomatisationYupeng CAO (1), Weiren LIN (1), Feng ZHANG (2)1: Graduate School of Engineering, Kyoto University, Japan; 2: Department of Civil Engineering, Nagoya Institute of Technology, JapanAn example of calibrating physical parameters in a constitutive model based on machine learning framework1221 In order to more accurately describe the behavior of geological materials, constitutive models with increasing complexity are being developed. The increase in the number of parameters and equations makes engineering applications difficult. On the other hand, data-driven machine learning approaches have shown great potential in addressing this issue. Therefore, from a data perspective, this paper recapitulates and discuss the task and framework of machine learning. For the parameter calibration task, 1-Dimensional Convolutional Neural Networks (1D-CNN), Recurrent Neural Network (RNN), Genetic Algorithm (GA), and Particle Swarm Optimization (PSO) were tested under the framework of representation learning and optimization. In the preset computing environment, the normalized RMSEs of representation learning are 0.21 and 0.17, and the calculation takes less than 0.1 second. Optimization frameworks perform better with RMSEs of 0.04 and 0.07, but cost over 10 hours. Finally, the advantages and disadvantages of each framework are discussed. | Machine Learning. Constitutive Model. Parameter Calibration. Representation
T13: Numerical methods in rock engineeringSergio PALMA (1), Rodolfo MORALES (2)1: Universidad Técnica Federico Santa María, Chile; 2: Universidad de ChileMathematical model to describe the movement of rocks due to gravity in block caving mining1222 Chuquicamata, located in northern Chile, has recently started operating as an underground mine using the Block Caving method. In this work, a new mathematical model is proposed to explain the phenomenology observed in the gravitational flow of fractured rocks in block caving mining. We propose that the tensional state and gravity originate a driving force greater than the resistance developed at the boundary of the group of fluidized rocks. The dynamics is controlled by a dimensionless number Y obtained as the ratio between the driving and resisting forces. If the frictional force at the interface has a viscous component proportional to the relative speed of the fluidized rocks, an analogous equation to Darcy’s law for the flow of a Bingham fluid in a porous medium is recovered. The model was numerically solved using FEM, achieving an adequate reproduction of the results of Fullard et al. (2019), for the velocity field. | Block caving mining, fractured rocks, granular, velocity field
T15: Rock and rock mass propertiesSair KAHRAMAN (1), Egemen SAYGIN (2), Mustafa FENER (3)1: Hacettepe University, Turkey; 2: RPM Global-Turkey; 3: Ankara University, TurkeyThe influence of microwave treatment on the Cerchar abrasivity of igneous rocks1223 This study investigates the effect of microwave treatment on the Cerchar abrasivity index (CAI) of igneous rocks such as granite, syenite, and gabbro. First the mineral contents and percentages of each rock were determined. Then, microwave treatment was applied on the specimens broken in the indirect tensile strength for 180s at the microwave powers of 2 kW and 6 kW. The evaluation of the test results shows that the CAI values of the specimens decrease with increasing microwave power. The CAI losses increase generally with the increasing surface temperature and the microwave power depending on the mineral contents. Concluding remark is that microwave treatment decreases the CAI values of igneous rocks. However, further study should be carried out to determine the CAI loss for different rock types at different exposure times and microwave powers. | Cerchar abrasivity, Igneous rocks, Microwave treatment, Mineral contents
T06: Geological investigation and characterizationGeorg H. ERHARTER (1,2), Tom F. HANSEN (1), Shengwen QI (3), Neil BAR (4), Thomas MARCHER (2)1: Norwegian Geotechnical Institute, Oslo, Norway; 2: Graz University of Technology, Institute of Rock Mechanics and Tunnelling, Graz, Austria; 3: Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Aademy of Sciences, Beijing, China; 4: Gecko Geotechnics, Cairns, AustraliaA 2023 perspective on Rock Mass Classification Systems1224 Dozens of rock mass classification systems (RMCS) have been developed since the 1950s for applications like tunnelling, mining or rock slopes. The abundance of systems and ongoing discussions amongst scholars and practitioners are symptomatic of the complexity of the problem and show that the community has not converged to commonly accepted procedures. Based on an online survey, this study aims to give an overview of the international spread of RMCS in use. The survey shows that GSI, RMR and the Q-system are the dominating systems in the world for underground engineering- and slope-related applications and thus have managed to prove their practical applicability throughout up to five decades. Conversely, the survey highlights that almost no system developed in the past 25 years has become internationally accepted, thus raising the question of whether today's RMCS can still live up to technological and scientific standards in 2023? | Rock Mass Classification, Tunnelling, Slopes, Mining, World Map
T08: Hydropower projects and damsRujiu ZHANG (1), Wenyu ZHUANG (1), Jianjun XU (2), Liang YIN (2), Haining WEI (2), Yaoru LIU (1)1: Tsinghua University; 2: POWERCHINA Huadong Engineering Corporation Limted.Deformation behavior analysis of an arch dam during initial impoundment based on clustering and panel data regression1228 Deformation behavior analysis is crucial for ensuring safe operation of the arch dam. This study investigates the deformation distribution and influencing factors of an arch dam in southwest China based on k-means clustering analysis and panel regression models. Results show that dam deformation is closely related to the impounding process and reservoir water level is the main influencing factor. The deformation of some monitoring points near the dam foundation are also affected by aging component. The effects of temperature are negligible in the short term. In general, the studied arch dam is in a condition for safe operation; the abnormal deformation of some monitoring points is basically affected by unbalanced hydraulic thrust, whose magnitude is small and tends to be stable. Analysis results also validate the applicability of cluster analysis and panel regression model in the evaluation of arch dam deformation behavior during initial impoundment. | arch dam, deformation behavior, panel data, k-means cluster, initial impoundment
T15: Rock and rock mass propertiesKai ZHANG (1), Ling ZHU (2), Li CHENG (3), Qingchao LYU (4), Yaoru LIU (1)1: Tsinghua University, People's Republic of China; 2: Hydropower Engineering Technology Research Center, Academy of Science and Technology, China Three Gorges Corporation; 3: China Renewable Energy Engineering Institute; 4: Powerchina Northwest Engineering Corporation LimitedEffect of normal stress on dynamic friction weakening of granitic rock joints under cyclic shear1229 The friction strength evolution of rock joints subjected to cyclic dynamic loads is very vital to the safety and stability assessment of rock engineering during earthquakes and rock bursts. In this paper, cyclic shear experiments under different normal stress were carried out for granite joints based on a shaking table apparatus. The frictional behavior under cyclic shear, especially the dynamic evolution of friction strength, was investigated and the effect of normal stress on friction strength weakening was quantified. Based on experimental results, a hysteresis model is used to characterize the dynamic friction behavior of planar joints under cyclic shear. This model relates the evolution of friction strength to the number of cycles of cyclic shear. As the normal stress increases, the strength weakening ratio increases correspondingly, while the critical number of cycles (at which the residual strength is reached) remains essentially unchanged. | Rock joints, Dynamic friction, Cyclic shear, Normal stress
T14: Petroleum engineering and carbon sequestrationLichun JIA, Dengyun LU, Gui TANG, Changhong ZHOUDrilling & Production Technology Research Institute, CNPC Chuanqing Drilling Engineering Company Limited, People's Republic of ChinaAnalysis of time-dependent wellbore instability with a porochemothermoelastic coupling model in tight gas reservoirs1233 Maintaining wellbore stability is a significant task during drilling. This study investigates time-dependent wellbore stability of a tight gas reservoir in central Sichuan Basin of China with a porochemothermoelastic model. The results show that breakout regions gradually enlarge and equivalent collapse pressure increases with exposure time. The breakout enlarge drastically in the first 5d and following a slowly enlargement from 5d to 10d and 30d. And the equivalent collapse pressure is higher than the mud density 1.45g/cm3 at inclination 46° to 80° for t=0d and at inclination 33° to 90° for exposure time 5d, 10d and 30d. Consequently, the mud density 1.65 g/cm3 of borehole inclination above 33° is recommended to stabilize the borehole. | porochemothermoelastic, wellbore stability, tight gas reservoirs, time-dependent
T13: Numerical methods in rock engineeringXin ZHANG, Guangyao SI, Joung OHUniversity of New South Wales, AustraliaThe correlation between aperture evolution and induced seismicity during simulated hydraulic fracturing in lab-scale coal samples1234 This paper successfully simulated the hydraulic fracturing process in lab-scale coal samples and induced seismicity using the self-developed code in particle flow code (PFC). Numerical simulations of fluid injection, fluid transport and seismic response are achieved simultaneously. The code has been applied to simulate water injection into an intact coal sample and coal samples with one pre-existing fracture. Model results satisfy observations from theoretical assumptions and laboratory experiments, which justifies the reliability of the proposed self-developed code. They indicate that hydraulic fractures on the side of the sample with a pre-existing fracture present different cracking propagation pattern compared to the other side with no pre-existing fracture. The pattern can be used to predict the impact of pre-fractures on the seismic extension-to-compression ratios and the aperture of hydraulic fractures. | Hydraulic fracturing, Seismicity, Pre-existing fracture, Particle flow code
T13: Numerical methods in rock engineeringXu LI, Guangyao SI, Joung OH, Ismet CANBULATUNSW, AustraliaPhase-field model of compressive and tensile fractures in ductile sandstone, calibrated by P wave velocity measurement and moment tensor inversion1235 Recently, a novel approach (phase field damage model) enabled the simulation of compression and tension-induced cracks quasi-statically and captured crack propagation within the FEM (finite element method) framework. However, the application of the phase-field damage model is restricted by the calibration of the crack diffusion parameter, which cannot be directly measured. In this study, we proposed a new elastoplastic phase-field damage model, calibrated from the AE (Acoustic emission) moment tensor inversion and ultrasonic wave velocity measurement. The phase-field damage variable is determined from P wave velocity measurement and acoustic moment tensor inversion. Specular decomposition is performed on the damaged tensor to distinct tensile and compressive microcracks. The evolution between tensile and compressive phase-field damage variables is hence to be considered independently. The proposed model shows great consistency with the laboratory observations and the application of the proposed model in COMSOL software enables to capture the quasistatic propagation of both tensile and shear fractures. | phase-field damage, seismicity, rock mechanics
T15: Rock and rock mass propertiesZhiqiang LIU (1,2), Linlin WANG (1,2), Shihui YU (1,2)1: China University of Petroleum-Beijing, People's Republic of China; 2: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China 2 China University of Petroleum, Beijing, ChinaLow-temperature Thermal diffusion in Rocks1236 At low temperature, frost weathering due to the freezing/thawing process of pore water can fracture bedrock permafrost, which is of crucial importance in engineering. We focus on the low-temperature thermal diffusion that is primarily fundamental but poorly investigated. The experiment and simulation investigations are conducted on sandstones subject to low-temperature conditions. It shows that the heat capacity of sandstones is more sensitive to temperature at the condition of the low temperature than that at the condition of the high temperature. The thermal conductivity of dry sandstone decreases with temperature at the condition of high temperature. However, it reveals that the thermal conductivity increases with temperature at the condition of low temperature. Besides, the temperature evolution curve for the water-saturated sample remains quasi-constant with the time when the phase transition occurs, which is governed by the pore-size distribution. | Heat transfer, Low temperature, Phase transition, Thermal conductivity
T16: Underground storage for liquid and gaseous mediaSophie MESSERKLINGER (1), Mikkel SMAADAHL (2), Daniel PÖTSCH (3), Carlo RABAIOTTI (2), Erich SAURER (4)1: University of Applied Sciences Upper Austria, Austria; 2: Eastern Switzerland University of Applied Sciences, Switzerland; 3: Salzburg AG, Salzburg, Austria; 4: Skava Consulting ZT GmbH, Salzburg, AustriaLarge rock caverns for heat storage in district heating networks – A comparative study for the city of Salzburg1237 Large heat storages play a key role for the implementation of renewable energy and industrial waste heat in heat distribution networks. One option is to use underground space for large heat storages. In this paper a case study for large underground heat storages in the heat distribution network of Salzburg is presented. Possible locations for large underground heat storages along the existing heat distribution network were identified, also based on the geological conditions. Two locations were selected and the temperature distribution in the underground around the heat storage cavern was numerically simulated using COMSOL with the aim to determine the energy losses and the temperature change at the ground surface. The results showed that the energy losses can be reduced considerably by >70% compared to insulated steel tank storages and that the surface temperatures are not much influenced by the heat storage below. | heat storage, rock cavern, shaft, numerical simulation, energy losses
T15: Rock and rock mass propertiesXunhui XU (1), Weiren LIN (1), Han BAO (2), Peijie YIN (2)1: Kyoto University; 2: Chang'an UniversityFlow simulation in digital rough fractures by considering anisotropic roughness and geometrical combinations1238 Anisotropic flow behavior in rock fractures is playing an important role in resource exploitation and engineering. To better understand the relation between flow behavior and geometrical features of fractures, digital fractures with 3 roughness were generated based on the spectral method. Simulation was conducted on 3 constant velocity inlets. From the results, flow behavior in 4 fracture pairs all show anisotropy in opposite directions. Different flow behaviors of the walls swapped fracture pairs indicate the influence of normal vectors of fracture asperities. Ratios of the roughness parameter M between upper and lower fracture walls are correlated to flow pressure gradient. | Rock fracture, flow simulation, anisotropy, pressure gradient, roughness
T15: Rock and rock mass propertiesPeiwang CAO (1), Tao ZHOU (2), Rui LI (1), Jianbo ZHU (2)1: State Key Laboratory of Hydraulic Engineering Simulation and Safety, School of Civil Engineering, Tianjin University, Tianjin, China; 2: Institute of Deep Earth Sciences and Green Energy, College of Civil and Transportation Engineering, Shenzhen University, Shenzhen, ChinaEffect of loading rate on dynamic mixed mode I/II fracture behavior in rock1239 Dynamic mixed mode I/II fracture of rock is quite common in rock engineering due to various dynamic disturbances. However, the understanding of rate effect of mixed mode I/II fracture behavior in rock is still at its infancy. To investigate mixed-mode fracture under different loading rates, the split Hopkinson pressure bar tests were conducted on cracked straight through Brazilian disc sandstone specimens. The results show that the crack propagation velocity, mode I and mode II stress intensity factors, dissipated energy increase with increasing loading rate. The effect of loading rate on crack propagation path is slight. The changes in micromorphology of rock may be the main reason for the rate effect of fracture. Findings in this work can help understand the dynamic mixed mode I/II fracture in rock engineering subjected to high loading rates. | Mixed mode I/II fracture, Stress intensity factor, Rate effect, Rock material
T13: Numerical methods in rock engineeringUn Chol HAN (1), Kum Il PAK (2), Kun Ui HONG (2), Chol RI (2), Il Yong KANG (1), Shang Guk CHOE (3), In Jun RI (3), Yong Il RI (4)1: School of Science and Engineering, Kim Chaek University of Technology, Democratic People's Republic of Korea (North Korea); 2: Faculty of Mining Engineering, Kim Chaek University of Technology, Democratic People's Republic of Korea (North Korea); 3: Shangnong Mine, Democratic People's Republic of Korea (North Korea); 4: Faculty of Anthracite Mining Engineering, Pyong Song University of Coal Mining, Pyongsong, Democratic People's Republic of Korea (North Korea)Numerical analysis of pillar stability for safe mining of a combined mine based on three-dimensional solid model1240 In this paper, we propose a fast and a convenient modeling technique that combines the unique advantages of ANSYS and FLAC3D in numerical calculation and those of SURPAC in 3D modeling. First, the relationships between the data structures of the model files for SURPAC, ANSYS and FLAC3D were examined, and the transformation technique of integrated 3D solid model was given via Excel. Then, the proposed method was applied for analyzing the pillar stability for sublevel open stope method in 0# upper level of the target mine. From the simulation results, heights of the upper and lower chain pillars, width of interchamber pillar for the stope were all set to 8 m, and length and height of the stope were 60 m and 50 m, respectively. Finally, we have verified the validity and feasibility of the proposed model transformation technique and the accuracy of numerical simulation could be further improved. | Integrated 3D solid model, Numerical simulation; SURPAC, FLAC3D, model transformation
T14: Petroleum engineering and carbon sequestrationNazir MAFAKHERI BASHMAGH (1), Weiren LIN (1), Abbas KHAKSAR MANSHAD (2)1: Kyoto University, Japan; 2: Petroleum University of Technology, IranDetermining the Magnitudes of Maximum and Minimum Horizontal Stresses from Borehole Data: Comparison Between Borehole Failure Approach and Poroelastic Strain Model1246 This paper compares the magnitudes of horizontal stresses estimated by the poroelastic horizontal strain model and borehole breakout approaches in one of the oil wells near the Zagros suture zone. First, the poroelastic horizontal strain model was utilized for determining the magnitude of maximum horizontal stresses, using vertical stress, pore pressure, and physical properties of the rock determined based on wireline logs. Then, the breakout approach was employed to determine the magnitude of horizontal stresses. The R2 of the linear regression between the two methods for minimum and maximum horizontal stress was 0.74 and 0.71, respectively. Even though there are different correlations in some depths, the consistency is generally significant, and stress regimes in both methods were consistent in almost all intervals. The results show this method's capability to calibrate the poroelastic strain method using the breakout approach continuously. | Rock failure, In situ stress, poroelastic strain model, Borehole compressive failure
T06: Geological investigation and characterizationCatherine DORÉ-OSSIPYAN (1,2), Jean SULEM (1), Michel BORNERT (1), Alexandre DIMANOV (2), Patrick AIMEDIEU (1), Vincent DE GREEF (2), Andrew KING (3)1: Laboratoire Navier, Ecole de Ponts Paristech, France; 2: Laboratoire de Mécanique des Solides, Institut Polytechnique de Paris, France; 3: Psiche beamline, Synchrotron Soleil, Saint Aubin, FranceMulti-scale analysis of a porous carbonate rock under triaxial conditions1247 The formation and evolution of deformation bands in a carbonate rock with high porosity is investigated by performing in situ triaxial experiments with high-resolution synchrotron X-Ray Computed Tomography by placing a specifically designed testing device directly in the tomograph. The processing of images by Digital Volume Correlation techniques provides insight on the deformation modes of the samples for various loading conditions. In more porous specimens with a homogeneous microstructure, many subhorizontal compactant deformation bands sequentially initiate, propagate, widen and fully saturate the volume of the rock sample after a few percent of overall strain. This leads to a rather uniform compaction of the sample. In contrast, denser samples with a more heterogeneous microstructure exhibit discrete deformation bands, in limited number. These bands propagate and widen, leading to strong localization of the deformation which remains restricted to certain parts of the sample. | in situ triaxial test, compaction bands, carbonate rocks, Digital Volume Correlation
T07: Geological risks and natural hazardsChristian BINDER, Anna FREUIS, Michael SCHREINER, Mathias SMESNIKAFRY Austria GmbH, AustriaRockfall hazards – Risk assessment, benefit/cost analysis and the design of flexible rockfall protection systems1248 Rockfalls are a major threat to society and infrastructure in mountainous regions. The extension of settlement areas, linked with an increase in traffic combined with the people’s need for safety while driving on roads, make rockfall risk assessments and the employment of technical rockfall protection solutions indispensable. However, it is impossible to eliminate all economic and social risks caused by rockfall in mountainous regions. Risk assessments combined with benefit/cost analysis aim to reduce the risk in a structured and transparent framework to an acceptable level while maintaining cost efficiency. Technical risk reduction solutions like flexible rockfall barriers, etc. are effective but costly considering the initial investment and maintenance. This paper discusses the methodology and elements of a conducted risk assessment along with a benefit/cost analysis and how the same was used in the decision-making process of a rockfall hazard mitigation project for a section of a federal road in Austria. | Natural Hazards, Rockfall, Risk Concept, Risk Assessment, Benefit/Cost Analysis
T09: Long term behaviour of underground structuresRaphael SCHARF (1), Bernhard PICHLER (1), Roman HEISSENBERGER (2), Bernd MORITZ (2), Christian HELLMICH (1)1: Institute for Mechanics of Materials and Structures, TU Wien (Vienna University of Technology), Vienna, Austria; 2: ÖBB - Infrastruktur AG, Streckenmanagement und Anlagenentwicklung, Fachbereich Bautechnik - Tunnelbau, Graz, AustriaData and analytical mechanics: a new look on NATM tunnels1251 Hybrid methods, i.e. combinations of deformation measurements with structural and material mechanics have been successfully used, for more than 20 years, for the New Austrian Tunneling Method (NATM), and beyond. This contribution extends these developments with respect to the mechanical behavior of such structures for more efficient evaluation of long-term behavior. In detail, internal shell-specific forces derived from the principle of virtual power are analytically linked, based on an aging viscoelastic material model, to radial and circumferential displacement components which were measured at selected points of the tunnel shell. For the Sieberg tunnel the data-driven analytical mechanics model evidences virtually uniform ground pressure distributions, leading to a ﬁrst rapidly increasing, and then mildly decreasing utilization degree of the shotcrete shell. | analytical mechanics, New Austrian Tunneling Method, aging viscoelasticity, shotcrete
T15: Rock and rock mass propertiesSamer ABOU KHEIR (1), Andrea BROGIATO (1), Patrick LIGNIER (2), Angelo LAMBRUGHI (3), Gabriele DE CARLI (4), Mark DIEDERICHS (5), Ivan CHING (6), Damiano FRONTINI (7)1: Tractebel Engineering S.A, Gennevilliers, France; 2: Tractebel Engineering S.A, Lyon, France; 3: Webuild S.p.A, Milan, Italy; 4: Webuild S.p.A, Rome, Italy; 5: Queen’s University, Kingston, Canada; 6: Snowy Hydro Limited, Cooma, Australia; 7: Future Generation Joint Venture, Cooma, AustraliaAssessment of the creep behavior of siltstone for the Snowy 2.0 hydropower station using multistage uniaxial and triaxial creep tests1252 The creep behavior of the siltstone rock type formations at the site of the Snowy 2.0 hydropower station was studied through multistage uniaxial and triaxial creep tests. The tests were conducted for up to 4 months to assess the effect of creep on the siltstone and to evaluate the impact on the short-term parameters. Samples were collected from boreholes located 650-850 meters beneath the surface from the Ravine Beds Unit formation and found to be composed of siltstone with interbedded sandstone (70/30% average). The siltstone was characterized by medium strength, a stiff matrix, and low porosity. The results of the creep tests showed negligible secondary creep deformations after full development of the primary stage. Additionally, the effect of confining pressure on creep behavior and deformation amplitude was also investigated. These tests provide valuable information to better understand the behavior of the siltstone rock type and its impact on underground excavation. | multistage triaxial creep test, multistage uniaxial creep test, siltstone, hydropower station, creep behavior
T13: Numerical methods in rock engineeringThedy SENJAYA (1), Ridho Kresna WATTIMENA (1), Nuhindro Priagung WIDODO (1), Devi KAMARATIH (1), Nisrina Zaida ULFA (2)1: Bandung Institute of Technology, Bandung, Indonesia; 2: PT Aneka Tambang Tbk, Jakarta, Indonesia2-Dimensional and 3-Dimensional Drawdown Analysis of Sediment Dam1253 This study analyzes the stability of four sediment dams (A, B, C, and D) at PT XYZ, using two-dimensional and three-dimensional limit equilibrium methods. The scenarios considered are existing condition, rapid drawdown, one empty pond, and pond at full capacity containing water/slurry from mining activities. The results indicate that the factor of safety is lowest in the rapid drawdown scenario, followed by one empty pond, existing condition, and full capacity ponds. The average difference in factor of safety between the existing condition and rapid drawdown is 0.31. The presence of water/slurry increases the normal stress on the dam, resulting in a higher factor of safety for the full ponds scenario. Surface-altering optimization is also used to enhance the accuracy of analyses. The study emphasizes the importance of considering multiple scenarios when conducting geotechnical analysis for sediment dams, especially changes in water level. | dam stability, sediment dam, limit equilibrium method, rapid drawdown analysis
T04: Deep mining and tunnellingYang ZOU, Ping ZHANGLuleå University of Technology, SwedenAssessment of energy release and redistribution on excavation instabilities for underground mining1254 Energy considerations are essential for the evaluation of violent failures which are commonly encountered as mining goes deeper. To address the relationships among different energy components, a series of numerical models were conducted by using 3DEC and a script was developed for energy visualization. The theoretical and numerical results of the ratio between the released kinetic energy and the excavated strain energy were compared under elastic and plastic models. The distribution of stored elastic strain energy and dissipated plastic strain energy in the vicinities of openings with different shapes were also investigated. Furthermore, the efficiency of a latest destressing method as a proactive measure for seismic management was evaluated based on the energy redistribution patterns. This research can improve the understanding of the energy evolution near excavations and contribute to the evaluation of burst-proneness of excavations as well as effectiveness of rockburst mitigation measures. | Rock burst, Released energy, Dissipated energy, Destressing, Seismic management
T13: Numerical methods in rock engineeringHsin Chen CHOU, Cheng Han LIN, On Lei Annie KWOK, Yu Chao LIN, Ming Lang LINNational Taiwan University, Taipei, TaiwanFinite element analysis-aided performance examination of the umbrella arch method for tunneling through weak zone1255 The umbrella arch support is frequently used as the tunnel face support system in difficult ground conditions. The Dong'ao Tunnel of Taiwan, which traverses through two thrust faults and a series of well-developed fractured zones, provides an important database for developing an assessment approach based on numerical analyses. This study implements three-dimensional finite element analyses to evaluate and optimize the utilization of the umbrella arch method in the weak zones. Results show that the deformation of the excavation face at the vault can be reduced by approximately 40% with the installation of an umbrella arch system. Parametric analyses indicated that the spacing of the forepoling pipes dominates the ability to control the deformation, followed by pipe diameter and distribution angle. This study reveals that the finite element analyses can aid the performance examination and enable a more informed decision when the umbrella arch method is used for tunneling through a weak zone. | 3D finite element analysis, umbrella arch method, design optimization, weak zone, Dongao Tunnel
T15: Rock and rock mass propertiesAndrew Garnet CORKUM (1), Derek KINAKIN (3), Diego MAS IVARS (2)1: Dalhousie University, Canada; 2: BGC Engineering Inc, Canada; 3: SKB and KTH, SwedenIntact Strength Determination of Rock Containing Mesodefects using the Leeb Hardness Test1256 The strength of rock blocks containing structural flaws and defects, such as veins and healed fractures (mesodefects) is particularly important for sparsely jointed rock masses under high stress. The conventional UCS test is often unsuitable for providing an accurate measure of the intact strength for rock containing mesodefect and it is difficult to conduct tests on suitably large specimens to account for mesodefects. The Leeb Hardness (LH) test is proposed to provide a quantifiable estimate of intact strength for mesodefected rock. The LH test is a lightweight, compact rebound test that has been correlated to rock strength with a large database (~400 test records) of various rock types over a wide strength and hardness range. The effects of conducting LH tests in the proximity of mesodefects has been examined and the LH test has been used in this study to estimate the true intact rock strength of defected rock cores. | Leeb Hardness test, defects, intact rock strength, DFN
T10: MonitoringFerenc DEÁK (1,4), Ákos TÓTH (2), Tomas MÁRIK (3)1: SeklerGeo, Hungary; 2: TunnelTech Ltd., Hungary; 3: Geoinspect Ltd., Cech Republic; 4: Budapest University of Technology and Economics, HungaryDetermination and validation of Longitudinal Displacement Profile by in situ measurements at the M85 motorway tunnel1258 Tunnelling is an obviously three-dimensional process. Tunnelling in yielding ground also generates a 3D, bullet shaped zone of plasticity in soft rock, but also generates a bullet shaped fracture zones in the brittle rock masses. Longitudinal displacement profiles (LDP) characterize and describe the displacement history during tunnel excavation, including that occurring ahead of the tunnel face. Experimentally determined LDP provide a valuable database for validation of the tunnelling approaches. This study is presenting the in-situ measurements of two geotechnical instrumentation sections which includes MPBX extensometers and NATM pressure cells from the shallow depth M85 motorway tunnel which is excavated in soft ground and is situated beside Sopron city (Hungary). The measurement results give us opportunity to validate the LDP and to verify the tunnel support interaction with the tunnel excavation. The results show good qualitative and quantitative agreement ahead of the tunnel face. | Longitudinal Displacement Profile, MPBX extensometer, NATM pressure cell, deformation, excavation
T04: Deep mining and tunnellingAli HASHEMI, Neda DADASHZADEH, Kathy KALENCHUKRockEng Inc., CanadaAn implicit numerical modeling approach for destress blasting design optimization for tunneling and mine development in high stress conditions1259 Tunnelling and underground mine development in high-stress conditions are exposed to potential rockburst hazards. Rockburst risk management may include multiple hazard control and/or exposure management strategies. Rockmass preconditioning, such as destress blasting, is a tactical approach to hazard control by introducing blast-induced fractures to the rockmass. Introducing fractures softens the rockmass and reduces potential stored strain energy. This paper explores a case study where a large-magnitude rockburst occurred in the floor of a mine tunnel located approximately 2km below the surface, in a strong, massive rockmass. Subsequently, destress blasting was implemented in all active development headings for risk mitigation. This paper presents a geotechnical study to optimize the utilization of destress blasting. A detailed numerical modeling investigation with implicit representation of blast damage is done using a calibrated FLAC3D model. The influence of destress blast design on rock burst hazard potential is numerically studied and discussed. | Rockburst, Destress Blasting, Risk Management, Numerical Modeling
T17: Rock slope engineeringDragana SLAVKOVIĆ (1), Aljoša MITIĆ (2), Miloš MARJANOVIĆ (3)1: Institute of transportation CIP, Nemanjina6/IV, Belgrade, Serbia; 2: Central road laboratory LLC, Zivorada Petrovica 13, Novi Sad, Serbia; 3: University of Belgrade, Faculty of Mining and Geology, Djusina 7, Belgrade, SerbiaComparing different rock mass classifications using field and point cloud data on a rock cut1261 Classifying rock masses implies a systematic quantification of various field data, lately including point clouds acquired using LiDAR or photogrammetric techniques. They have been proven useful for extraction of additional information and more confident rock mass classification in inaccessible parts of the slope. In this work, a rock cut along the railway Knjaževac – Zaječar in Serbia was analyzed using conventional field mapping and data extracted from point clouds. Basic RMR, SMR and Q-slope classifications were used for rock mass characterization. Extraction from the point cloud was applied beyond the accessibility line (>2 m), and included determination of RQD, joint spacing and orientation. The rock mass is split into three zones, wherein RMR score equaled 64, 57, and 56 for Zone 1, 2 and 3, respectively, whereas SMR score equaled 49, 42, and 41, respectively. A better distinction between the zones was achieved using Q-slope score, totaling 1.75, 0.66 and 0.31, respectively. | Rock Mass Classifications, RMR, SMR, Q-slope, LiDAR
T04: Deep mining and tunnellingEmeline LHOUMAUD (1), Yann GUNZBERGER (1), Jannes KINSCHER (2), Marianne CONIN (1)1: GeoRessources lab, Université de Lorraine - CNRS, Mines Nancy, Campus ARTEM, Nancy, France; 2: Institut National de l’Environnement Industriel et des Risques (INERIS), Campus ARTEM, Nancy, FranceOrigin of seismic repeaters in a deep mine: what do we learn from in-situ investigation coupling geology, geomechanics and geophysics?1262 Seismic repeaters (i.e. seismic events with highly similar waveforms) have been observed in the deep mine of Garpenberg, Sweden. In natural seismology, repeaters are commonly associated with the presence of aseismic slip (i.e. creep) on fault planes, loading seismogenic asperities. This raises questions regarding what these asperities and creeping zone consist of and how they behave from a mechanical point of view. A local monitoring network has been installed in situ, close to the source area of one family of repeaters at 1km depth, with the objective of identifying the origin of these repeaters. The network comprises boreholes, geophones and strain cells. We show that the presence of a fault plane with creeping portions and an asperity is compatible with field data. We also discuss the difficulty of clearly identifying the origin of the repeaters, as we couldn’t reach the seismic asperity itself, even with such a local network. | Induced seismicity, seismic repeaters, deep mining, in-situ investigation
T07: Geological risks and natural hazardsMatthias J. REBHAN (1), Hans-Peter DAXER (1), Markus SCHUCH (2), Franz TSCHUCHNIGG (1), Roman MARTE (1)1: Graz University of Technology, Austria; 2: ÖBB Infrastruktur AG, AustriaDevelopment of a double-corrosion-protected self-drilling micropile for the foundation of rockfall protection structures1263 The construction of protective structures is one of the most important tasks of engineers in the field of natural hazard management. In addition to the often adverse environmental conditions during the installation of these structures, the inspection and the maintenance of such constructions is associated with a high level of effort. This paper presents a newly developed foundation method in the form of a self-drilling, double-corrosion-protected micropile. This component is expected to make a significant contribution in ensuring the durability of protective structures and a sufficient planned service life of more than 30 years. In addition, a brief outlook into the field of loads on protective structures and the suitability and acceptance testing of micropiles is given. Finally, the current status of the further development of the newly conceived micropile and the possibilities that such a system can offer are discussed. | micropiles, rockfall protection, corrosion, corrosion protection, foundation
T07: Geological risks and natural hazardsAhmed HOSNI, Claire MYR, Bastien COLAS, Isabelle HALFON, Yannick THIERY, Karim BEN SLIMANEBRGM, 3 avenue Claude Guillemin, Orléans, FranceStudy of the influence of anthropogenic galleries on the chalk cliff stability at Normandy region (France)1264 The chalk cliffs are regularly subject to mass collapse phenomena in Normandy region (France). These instabilities represent some problems to manage for local authorities. In some cases, the chalk cliffs contain one or more galleries of anthropogenic origin and hazard assessment should integrate these particular contexts. Numerical modelling was developed in 2022 in order to quantify the influence of galleries on cliff’s stability. We studied the behavior of the {cliff + gallery} set according to parameters as the dimensions of galleries, their direction in comparison to the cliff direction (parallel or perpendicular), the superposition of exploited levels, the rock mass discontinuities, the mechanical properties of the overburden layers, etc. A scoring method is presented based on attribution of scores to the main parameters to determine the gallery influence on cliff’s stability. | Chalk, Cliff, gallery, stability, fracture, collapse, numerical model, distinct element method, plastic, mechanic, scoring
T01: Challenging rock engineering projectsAfshin ARABZADEH, Xavier DONTIGNY, Marianne DEBELNouvLR, CanadaThe effect of TBM tunneling on the surface and underground deformations under Montreal-Trudeau international airport (YUL) runway1265 The Réseau Express Métropolitan (REM) is a light rail system that spans 67 km and will link the Pierre-Elliot-Trudeau International Airport to the greater Montreal area. As part of the system, a 3 km tunnel starting at the Marie-Curie station is being built by a TBM machine with a diameter of 7.37 m to join the airport station. The tunnel alignment passes under airport runway 06L/24R. To estimate the effects of TBM tunneling on surface subsidence under runway 06L/24R, a 2-D numerical analysis was conducted using the FLAC-2D code. Moreover, to monitor the surface and ground movements by TBM tunneling, geotechnical instruments as well as radar imagery InSAR system were installed along the tunnel alignment. The numerical modelling results show that the induced ground surface settlements for runway 06L/24R caused by TBM tunneling is negligible and the results obtained from geotechnical instruments were validated against the numerical analysis findings. | TBM tunneling, numerical analysis, geotechnical instruments, surface subsidence, underground movement
T12: New developments in rock supportHonghao CHEN (1), Hamed Lamei RAMAND (1), Imrana KABIR (1), Onder KIMYON (1), Ren CHEN (1), Naresh KUMAR (1), Cindy GUNAWAN (3), Peter CRAIG (2), Ismet CANBULAT (1), Micheal MANEFIELD (1), Serkan SAYDAM (1)1: University of New South Wales, Australia; 2: Jennmar Australia; 3: University of Technology SydneyPrevention of catastrophic corrosion failure of rockbolt and cable bolt in underground coal mines1268 The catastrophic corrosion failures of rockbolts and cable bolts in underground coal mines have been reported from several mines in the past few decades. Many of the failed bolts have been in service for a short period. The preliminary studies have found that the failures occur by hydrogen-induced stress corrosion cracking (HISCC) and microbial-induced corrosion (MIC). In these types of failures, the local environment where the bolt was installed is the key to initiating and accelerating the corrosion process. This study investigates the capabilities of polymer coating and galvanising technologies for preventing bolt corrosion failures. We use our previously developed HISCC and MIC reproduction method to reproduce the corrosive environment in the lab. The laboratory study shows the benefit of polymer barrier coating compared to galvanising in an extreme environment, and it also has good resistance to MIC. | Ground support safety, corrosion, rockbolt, cable bolt, stress corrosion cracking, microbiological induced corrosion
T17: Rock slope engineeringHiroyuki HONDA (1), Yasuhiro MITANI (1), Hisatoshi TANIGUCHI (1), Ibrahim DJAMALUDDIN (2), Yurino KAWAURA (1)1: Kyushu University, Japan; 2: Hasanuddin University, IndonesiaRock slope stability management along the road by machine learning through databasing disaster prevention records1269 In the maintenance of roads through mountainous terrain, inspections for rockfall and rock collapse are not conducted on all the targeted roads, thus resulting in disasters outside the scope of the inspections. In this study, 0.5 m Laser Profiler (LP) along National route 210, Oita, Japan, with a total length of 100 km is applied to generate Digital Elevation Model, and the division of slope units is created based on the inclination angles and their distribution. Secondly, the database is prepared by the inspection records (2006-2021) that machine learning will use as training data to create a risk evaluation model. Finally, we were able to extract potentially dangerous slopes that have not been inspected so far in the study area and clarified the inspection priority. | steep cliff, rockfall, rock collapse, road disaster prevention record, supervised learning
T13: Numerical methods in rock engineeringShuai ZHANG (1), Yongcun FENG (1), Tao XIE (2), Qi HE (1), Hai LIN (2)1: China University of Petroleum,Beijing, China; 2: Tianjin Branch, CNOOC (China) Co., Ltd., Tianjin, ChinaThe effect of temperature on lost circulation through induced fractures - a fully coupled THM model1271 The exploitation of deep oil and gas resources has attracted increased attention. When drilling, a high frequency of lost circulation results from the features of high temperature, high pressure, and high stress, where the temperature is an important factor that cannot be disregarded. The effect of temperature on drilling fluid loss law as well as the influence of temperature difference on fracture initiation, fracture geometry, and fracture extension rate is investigated using a fully coupled Thermal-Hydrological-Mechanical (THM) model built using the finite element method. The simulation results demonstrate that the temperature effect can dramatically lower the lost flow rate. Only when the flow rate is low does temperature dominate the lost fracture extension, which is then divided into the flow-rate dominance stage and temperature dominance stage under high flow rates. | Lost Circulation, THM, Fracture Propagation, Dynamic Circulation, Finite element method
T13: Numerical methods in rock engineeringKazuya ISHITSUKA, Hitoshi MATSUI, Weiren LIN, Nana KAMIYA, Yoshitaka NARAKyoto University, JapanSeismic velocity estimation using a digital rock without segmentation - tips for accurate calibration and estimation1272 Estimating physical properties of rocks from X-ray CT images is useful when preparation of rock core specimens for lab measurement is difficult. In this study, we examined and extended the recently-proposed segmentation-less method to construct digital rock model for seismic velocity estimation. We first examined the effectiveness of the method to two sets of CT images of Berea sandstone with voxel resolutions of 7 and 11 μm, respectively. We further applied the method to Kumamoto andesite to examine its effectiveness to a volcanic rock. Our results showed that the method successfully estimated P-wave velocity of these cases. The setting of the parameters to link CT values to mineral phase was important, and the parameter setting was linked with the internal structure of the volcanic rock. A proper knowledge of pore and mineral properties of the rock of interest is useful for accurate seismic velocity estimation by the segmentation-less method. | Digital rock, Seismic velocity, X-ray CT, Sandstone, Andesite
T04: Deep mining and tunnellingHongpu KANG, Yanjun FENG, Fuqiang GAOChina Coal Research Institute, People's Republic of ChinaApplication of hydraulic fracturing for destressing mining-induced stresses in underground coal mines1273 Hydraulic fracturing (HF) has emerged as a widely used ground control strategy in Chinese coal mining practice, often employed in combination with ground support techniques. HF campaigns can be broadly categorized into two types based on the size of the targeted region: local campaigns, which are applied to smaller areas such as the roof above a coal pillar, and large-scale campaigns, which encompass a broader area, such as the entire width of a longwall panel. This paper presents two case studies that examine the use of both local and regional HF as a ground support strategy in Chinese coal mines. The field studies demonstrate that HF is effective in reducing or redistributing mining-induced stresses, preconditioning hard rock strata, and, in some cases, decreasing mining-induced microseismicity. | hydraulic fracturing, underground coal mine, destressing, case study
T14: Petroleum engineering and carbon sequestrationShouding LI (1,2,3), Zhiquan YU (4), Supeng ZHANG (1,2,3), Jianming HE (1,2,3), Zhaobin ZHANG (1,2,3), Xiao LI (1,2,3)1: Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China; 2: College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China; 3: Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing, China; 4: Inspur Group Co Ltd, Jinan, ChinaMechanical anisotropy and tension-shear characteristics of shale in Pengshui area, Chongqing1277 As an unconventional energy, shale gas is being developed widely. As one of the core means of development for shale gas, hydraulic fracturing is greatly affected by the mechanical properties of shale, especially its anisotropy and shear characteristics related to the activation of natural structural planes. In this paper, the law of anisotropy characterized by wave velocity and its ratio of shale is summarized through the analysis for the velocity of P-wave and S-wave, the strength characteristics of shale under tension-shear condition is also obtained through the mechanical tests on shale samples in different directions. | Shale, mechanical characteristics, anisotropy, tension-shear
T06: Geological investigation and characterizationYusuke HIRATSUKA, Sou KUMAMOTO, Hajime YAMAMOTOTaisei Corporation, JapanDevelopment of "T-DrillPacker" measurement system for groundwater inflow rate and pressure in advanced boring1279 Large groundwater flow into the tunnel during construction of a mountain tunnel can cause crucial problems. It is therefore important to investigate the location, flowrate, and hydraulic pressure of the flow paths ahead of the tunnel face in advance to tunnel excavations. One of the effective ways to characterize the flow paths is measurement of flowrate and pressure in the advanced horizontal boreholes using a packer system. However, with the conventional method, it is often difficult to carry out the installation of packer systems due to the risks of borehole collapse and delay in the construction schedule caused by pulling out the drilling string before packer installation. Therefore, the authors have developed a new measurement system that can be installed packer without pulling out the drilling tools. This paper describes the concept of this system, and a result of its successful application to a mountain tunnel construction site. | NATM, Advanced boring, Groundwater inflow rate, Hydraulic pressure, Packer system
T04: Deep mining and tunnellingFuqiang GAO, Guiyang YUAN, Xiangyuan PENGChina Coal Research Institute, People's Republic of ChinaExperimental study of coal bursts caused by decrease of local mine stiffness1281 The crucial role played by local mine stiffness (LMS) in the occurrence of rock strainbursts has been widely acknowledged. To prevent rockbursts, it is essential to comprehend the evolution of LMS during mining operations. Unfortunately, existing studies on this subject are largely limited to theoretical and numerical methods. To address this research gap, we conducted an experimental investigation using an in-house developed equipment. The aim was to generate strainbursts resulting from excavation-induced stress concentration and LMS reduction. In this study, we simulated the excavation process and associated disturbances using real coal blocks in a laboratory setting. The results of our experimental investigation provide a novel approach for producing strainbursts that arise due to the progressive reduction of local mine stiffness during mining operations. | strainbursts, local mine stiffness, experimental study, stress concentration
T13: Numerical methods in rock engineeringKun Ui HONG (1), Chung Song CHOE (1), Chung Il KIM (1), Un Chol HAN (2)1: Faculty of Mining Engineering, Kim Chaek University of Technology, Democratic People's Republic of Korea (North Korea); 2: School of Science and Engineering, Kim Chaek University of Technology, Pyongyang, Democratic People’s Republic of KoreaFailure characteristics of rock mass around sublevel and shrinkage stopes in steep thick orebody using Surpac and 3DEC1283 This paper assesses the fracture development characteristics of the rock mass around the sublevel and shrinkage stopes under steep thick orebody using 3DEC and Surpac, and redetermines the boundary of the protective pillar area for the dressing plant. A 3D solid model was constructed using a laser detector and Surpac, transformed it into a 3DEC numerical model, and then the settlements and failure zones of the rock mass around the stopes were analyzed using generalized Hoek–Brown failure criterion. At that time, the mining characteristics of the orebody are 50–100m long, the bed height is 50m, the ore body thickness (M) is 10–30m and the slope angle is 60°. From the simulation results, the relative error between the simulated and the measured data was less than 10%. Finally, the mineable reserves of more than about 2 million tons in the protective pillar area can be obtained. | Fracture development characteristics, Stope stability, 3DEC, Surpac
T13: Numerical methods in rock engineeringMichel VARELIJA (1), Michael NÖGER (1), Philipp HARTLIEB (1), Peter MOSER (1), Dominik DENDL (2)1: Montanuniversitaet Leoben, Austria; 2: DSI UndergroundThe effect of different rock mass properties on deformation distribution detected with intelligent rock bolts in underground mining1284 Significant changes in stress distribution are caused by the mining excavation process, which could lead to instabilities. The conventional approach involves the installation of rock bolts along with other support measures. Technological advancement enables upgrading these bolts with low-cost sensors for measuring deformation and monitoring the overall bolt condition. The objective of this study is to show the potential of such intelligent rock bolts. To achieve this, we analyzed deformation readings obtained from simulated intelligent bolts in a simplified mining scenario, considering the effects of joint spacing, orientation, and the K factor. We used Itasca's Software 3DEC to simulate data acquisition based on standard measurement bolts which are already available but differ in measurement capacity from the new development proposed here. This approach has the potential to identify deformation patterns associated with specific failure mechanisms related to different geological structures. | Intelligent rock bolts, numerical modelling, deformation measurement, discontinuities
T06: Geological investigation and characterizationJ.C. GRESS (1), M. FERREIRA (1), R.M. FAURE (2)1: Hydrogéotechnique, Fontaines, France; 2: Ecole Nationale des Travaux Publics de l'Etat, Vaulx en Velin, FranceRelations between elastic waves speeds and densities1285 For civil engineers, working on rocks, it is important to understand how density varies in the rock mass volume. Direct in-situ measurements are not easy, because of very often coring difficulties. The in-situ measures of elastic waves speeds can be interesting, but we need strong correlations between speeds and rock densities. Many researchers have worked on the subject but none has given physical relationships explaining the relations they had observed. Working on Nafe and Drake empirical curves, it is possible first to find an empirical relationship between Poisson ratio and density. Then, will be presented physical relationships existing between these two types of speed and rock density. Based on them, a relationship between rock mass elastic modulus Emr and density will be proposed. And finally comparing it to the one given by Hoek, linking Emr and the Geological Strength Index GSI, a relationship between GSI and density will be deduced. | Waves, speeds, densities, elasticity, modulus
T09: Long term behaviour of underground structuresMountaka SOULEY (1), Minh-Ngoc VU (2), Gilles ARMAND (2)1: National Institute for Industrial Environment and Risks (Ineris), France, France; 2: Radioactive Waste Management Agency (Andra), FranceLong term behaviour based on a weakness planes approach: Constitutive model and application to a Meuse/Haute-Marne (France) URL drift1287 A constitutive model considering the natural and induced anisotropies in the short- and long-term behaviour is proposed by combining the elasto-visco-plasticity for rock matrix and weakness planes. The main assumption is that the failure of claystone material is due to the failure of the rock matrix and the fracturing along weakness planes. For intact matrix: (i) the short-term response includes the main mechanisms (transversely isotropic elastic, hardening, softening and residual plastic strain, brittle-ductile transition) evidenced in laboratory investigations, (ii) the long-term behaviour is based on Lemaître's model in agreement with the laboratory tests. The time-dependent response of weakness planes is described by the Maxwell’s model with a threshold. After checking the model on simple stress paths, its operational character is successfully demonstrated on the GCS drift (the more difficult to reproduce the overall observations). The computed convergences (and their ratio) and plastic zone extensions are consistent with the in-situ observations. | Constitutive model; Weakness planes, Plasticity, Time-dependent behaviour, M/H-M URL drift
T10: MonitoringSharla COETSEE (1), Priyanka NARSHAI (1), John-Philip TAYLOR (2)1: Reutech Mining, South Africa; 2: Reutech Radar Systems, South AfricaAn overview of RAR application for pit slope monitoring: with a focus on spatial and temporal resolution1289 An overview of Real Aperture Radar (RAR) for pit slope stability monitoring is provided, with a specific focus on spatial and temporal resolution based on the physics utilised by the system. For the purpose of this paper, the RAR system discussed is the Reutech Mining Modular Movement and Surveying Radar (MSR). The system is deployed at a position whereby it is mechanically steered to conduct sequential interferometric measurements to delineate deformation data from the pit slope. The area that may be scanned is definable, and comprises 186° in azimuth and 129° in elevation. The sample acquisition time (temporal resolution) is dependent on the scan rate. The spatial point resolution is defined by user selected options. The radar is georeferenced in order to allow for 3D identification of synthetic map points and therefore the interrogation of data from potential areas of concern, which may indicate instability of the pit slope. | Real Aperture Radar (RAR), spatial and temporal resolution, monitoring, deformation, instability
T17: Rock slope engineeringMarco BARLA (1), Santina AIASSA (2), Francesco ANTOLINI (2), Alessandra INSANA (1), Andrea PERINO (2)1: Dept. Of Structural, Geotechnical and Building Engineering, Politecnico di Torino, Italy; 2: Geosolving srl, Torino, ItalyDiscontinuum modelling of slope instability as a support tool for risk management1291 The definition of threshold values within an early warning system for monitoring of an instability phenomenon in nearly real time represents a key step. Several approaches exist in literature, among which numerical modelling for the simulation of instability scenarios is the least common. The present paper illustrates how discontinuum numerical modelling can be used as a support tool for risk management with reference to a slope instability case study. The aim is to investigate the displacement rate that can anticipate the instability phenomena. To highlight the reliability of the models, back-analysis of a past instability event is carried out and a time-scaling coefficient is defined, and eventually validated, to match numerical results and monitored data. Based on such results, that reproduce the slope displacement trends from triggering to collapse, thresholds and related timespans to be adopted within the existing monitoring system are suggested. | Slope Stability, Discontinuum Modelling, Risk Management, Thresholds
T17: Rock slope engineeringRyan Alexander ZIEBARTH (1), Andrew G. CORKUM (1), Ian R. STILWELL (2), Derek KINAKIN (2)1: Dalhousie University, Canada; 2: BGC Engineering IncA Parametric Study Illustrating the Effects of Moderately Anisotropic Rock Strength on the Stability of Large Slopes using Limit Equilibrium Analysis1292 Accounting for moderately anisotropic conditions where one or more dominant structure sets affect slope stability analysis is challenging. Most analysis methods and software assume isotropic behaviour that better suits randomly jointed rock masses. Some methods for assessing anisotropic formations (bedding, schistosity, etc.) exist, but the computationally expensive Synthetic Rock Mass approach is the only method to capture moderately anisotropic behaviour. Therefore, guidance is needed to identify when a rock mass is moderately anisotropic. The limit equilibrium method software Slide2 was used to perform a parametric study on the Generalized Anisotropic strength model for a hypothetical rock slope. The key contributors to determining if a rock mass is moderately anisotropic were the shear strength (cohesion only) of the weak plane was a quarter or less of the intact strength, the angular distance between two joint sets was approximately 30°, and the angle of anisotropy was within 15° of the slope face. | Rock mass strength, Anisotropy, Slope Stability, Slide2
T07: Geological risks and natural hazardsFelipe GOBBI (1), Bruno DENARDIN DA ROSA (1), Dione Henrique DIAS (1), Fabio BERTUOL (1), Nataly AYUMI TOMA (1), Adoniran COELHO (2)1: FGS Geotecnia, Brazil; 2: ValeURUCUM Mine: Rockfall protection and monitoring system1294 The access to Urucum mine is at the base of the Morraria de Urucum, composed of sedimentary rocks, a very steep rockface. Several rockfalls events in the past required that the company take action to mitigate risks, leading to a diagnostic and protective measures. Initially, the analyzes were based only on a point cloud, due access restrictions related to the pandemic period, resulting in a preliminary design of rockfall barriers and drainage. With the conceptual design, an extensive field mapping was performed, and the project revised, culminating in a drastic reduction of necessary interventions. The optimization it was possible through identification of differential weathering in the jaspilite strata, which allowed a new geomechanical model, better probabilistic analysis of block size distribution and thousands of rockfall simulations. This case is an interesting example of how the use of modern tools helps in projects, but it shows that they should be used with caution. | Rockfall, field mapping, point could, rockfall barrier, probabilistic analysis
T01: Challenging rock engineering projectsTanja SATTLER (1,2), Kurosch THURO (2)1: Baugeologisches Büro Bauer GmbH, Germany; 2: Technical University of Munich (TUM), GermanyAdvancements in drillability prediction for conventional hard rock drill and blast tunnelling – implementing automation into the equation1295 With tunnelling projects being part of critical infrastructural development, it is of uppermost importance to schedule the construction for an on-time delivery. Specifically, a reliable drillability prediction is indispensable to forecast advancement rates adequately. With the drillability being a very complex entity, predicting advancement rates is challenging, potentially leading to extensive additional cost and operational delays. Based on a case study from an Austrian tunnelling project, various influencing factors were examined. Comparing predicted with actual drilling velocities, it was shown that the actual drilling rates remained behind the expectations by about 20 %. The analysis clearly shows that the geological conditions are not responsible for these shortcomings, but the working process and the machine parameters including the degree of automation being significant factors of influence. | drillability, penetration prediction, drilling automation, collaring, drill and blast tunnelling
T18: Early Career Forum (Young Researchers)Ardita MALAJ, Skender ALLKJA, Iljana KERO, Julian BELLIU, Besian XHAGOLLIALTEA & Geostudio 2000, AlbaniaSkavica Hydropower plant, one of the most important energetical projects to be constructed in Albania1298 Skavica area is in the north-eastern part of Albania. This article aims to characterize the soils and rocks met in the area under study following the national and international building codes and standards, focusing on the characterizations of rock formations. The main works for the geological and geotechnical study for Skavica HPP project, included the data received recently from A.L.T.E.A. & Geostudio 2000 company investigation. These works comprised a careful geological mapping; geological drillings; trial pits; sampling; field testing (SPT, Lugeon test, Le franc test, borehole optical readings, seismic measurements including refraction and reflection measurements; geophysical measurements, electrical measurements etc...); laboratory testing. This article will present and include all of the findings of our study; the interpretation of field and laboratory testing results and recommendations of the engineering measures to be taken to ensure dam stability and reservoir water conservation. | geological investigation, rock formation, rock characterization, field testing, laboratory testing, dam stability
T13: Numerical methods in rock engineeringManuel Bernhard WINKLER (1), Thomas MARCHER (1), Ali YAZ (2)1: Graz University of Technology, Graz, Austria; 2: Instanbul Technical University, Istanbul, TurkeyAn iterative scheme for the determination of the conformal mapping coefficients used in closed-form solutions for tunnels with arbitrary geometry1300 In case of tunnels with arbitrary geometries, solutions for stresses and displacements in the tunnel exterior might be derived with the aid of the conformal mapping technique of the complex variable method. Thereby, the physical tunnel domain is mapped onto a fictitious unit circle domain on which the elastic potentials, as part of the final solution, are evaluated. The used mapping function involves complex mapping coefficients. In this paper an overview of analytical solutions for stress and displacements fields around tunnels is provided, from the early Kirsch solution to the solutions involving the complex variable theory and conformal mapping. A possible solution procedure for the determination of these mapping coefficients based on an iterative process including the solution of linear systems of equations is presented. The proposed solution procedure can be utilized for the determination of the mapping coefficients of various conformal mapping functions as defined in different closed-form solutions. | analytical solution, complex variable theory, conformal mapping, mapping coefficients
T03: Deep geothermal energyJustin MATTHEIS, Catharina DREXL, Martin POTTEN, Georg Maximilian STOCKINGER, Kurosch THUROChair of Engineering Geology, Technical University of Munich, GermanyBorehole stability in geothermal reservoirs – A combined laboratory and numerical approach1302 Despite the well-known geothermal potential in the North Alpine Foreland Basin, large scale exploration is still limited by the economic risk of well instabilities originating from inadequate prediction of the heterogeneous rock mass conditions in the reservoir. One decisive factor is the rocks toughness against fracture propagation. Hence, analogs to the reservoir rocks are subject to Semi-circular Bend tests to determine the required energy for tensile fractures (mode I) and accordingly Double-edge Notched Brazilian Disk tests for shear fractures (mode II). The subsequent finite-discrete numerical simulations, in which the experimental results are implemented, show varying fracture patterns in the rock mass caused by drilling. The fracturing depends on the rock type, the pre-existing discontinuities, and the stresses in up to 5 km depth. Further expansion of this investigation to other scenarios and rock types, paired with a reliable geological prediction, reduces the associated risks for deep geothermal projects. | geothermal reservoir characterization, borehole stability, fracture energy, laboratory tests, numerical FDEM modeling; North Alpine Foreland Basin (SE Germany)
T06: Geological investigation and characterizationMaria Teresa CARRIERO (1), Anna Maria FERRERO (2), Maria Rita MIGLIAZZA (1), Battista TABONI (2), Gessica UMILI (2)1: Department of Structural, Geotechnical and Building Engineering, Polytechnic of Turin, Turin, Italy; 2: Department of Earth Sciences, University of Turin, Turin, ItalyRoughness measure of a large in situ discontinuity surface by non-contact survey1303 Roughness of rock joint surface plays a key role in the stability conditions of rock slopes and it is commonly assessed on small portions of the outcropping surface or laboratory samples. However, roughness is naturally dependent on the considered scale, the analyzed surface sector (surface heterogeneity), and the direction of measurement (surface anisotropy). Therefore, the scale effect, heterogeneity and anisotropy should be quantitatively assessed to understand their role in shear resistance variations. This paper describes the surveys carried out on an extensive natural discontinuity in a slope along the Elva Valley Road (Northwestern Italy) subject to frequent and intense instability phenomena. A digital surface model (DSM) of the entire surface was obtained through UAV (Unmanned Aerial Vehicle) photogrammetric technique and the resulting point cloud was analyzed in order to measure the spatial variability of the surface roughness considering the different directions and the surveying interval. | Roughness, scale effect, Morphology, Non-contact survey
T15: Rock and rock mass propertiesMilorad JOVANOVSKI, Jovan Br. PAPIC, Igor PESHEVSKIUniversity Ss. Cyril and Methodius, Faculty of Civil Engineering, Republic of North MacedoniaPhysical modelling of bimrocks in large scale direct shear apparatus1304 Complex geological mixtures as bimrocks, composed of core block inclusions randomly distributed in a weaker matrix, are challenging issues for a proper characterization in a large scale relevant for rock mass range, as the overall behavior is strongly influenced by the presence of the rock fragments and by their volumetric block proportion. The article presents results from their physical modelling and tests in a large-scale direct shear box with dimensions 1,0x1,0x0,6 m, loaded with stresses in large span. The mixtures of blocks and matrix are modelled for values of volumetric block proportion of 5%, 15% and 35%. Results confirm that higher contents of volumetric block proportion lead to higher angle of internal friction and lower value of apparent cohesion, while the time of failure is longer for a higher volumetric block proportion. | Bimrocks, volumetric block proportion, physical modeling, shear strength, time of failure
T10: MonitoringEdo NOORDERMEER (1), Roland BEKENDAM (2), Karlijn BEERS (1), Auke NACHENIUS (1), Devrez KARABACAK (1)1: Fugro, The Netherlands; 2: GeoControlMonitoring the rock-mechanical safety of underground limestone quarries using fibre optic sensing technology1306 A fibre optic monitoring system has been installed in two limestone quarries in Valkenburg aan de Geul, The Netherlands, to monitor pillar stability and to give early warning of locations at risk of collapse. The system is highly sensitive and can detect creep deformation of the pillars as small as 1 micrometer. Measurements are displayed via a web-based data portal and alerts are triggered if the creep velocity exceeds pre-determined thresholds or if creep accelerates. We present the design of the monitoring system and results from the first three years of operation. We show examples of the natural behaviour of the pillars and we present a number of deviating patterns that sparked particular interest. We also share some lessons learnt that can be used when designing and installing similar systems in other quarries, caves or mines. | Monitoring, safety, limestone mining, fibre optics
T15: Rock and rock mass propertiesTimothy Robert Michael PACKULAK, Émélie GAGNON, Samuel Keith WOODLAND, Jennifer Jane DAYDepartment of Geological Sciences and Geological Engineering, Queen's University, CanadaApplication of Digital Image Correlation for Analysis of Anisotropic Materials Under Tension1307 Tensile strength of rock and similar materials is a critical material property in rock engineering design. Anisotropic materials do not necessarily follow the behaviour as originally assumed when the Brazilian Tensile Strength test was created; therefore, additional care is required when analyzing tensile strength measurements of these materials. This study presents guidelines and recommendations for the analysis of strain accumulation in disc specimens with anisotropic geological fabrics using 2-dimensional digital image correlation. In addition, strain maps of specimen faces generated with digital image correlation are used to corroborate the mechanistic behaviour of a proposed three part anisotropic tensile strength criterion. | Brazilian Tensile Strength, Laboratory Testing Procedures, Anisotropic Geological Fabric, Foliation, Digital Image Correlation, True Tensile Strength
T13: Numerical methods in rock engineeringAlexander POISEL (1), Gunter GSCHWANDTNER (2), Markus SITZWOHL (3), Oliver Kai WAGNER (4)1: IGT Geotechnik und Tunnelbau ZT GmbH, Austria; 2: Energie AG, formaly iC-Consulenten, Linz, Austria; 3: IGT Geotechnik und Tunnelbau ZT GmbH, Austria; 4: ÖBB-Infrastruktur AG, Graz, AustriaSemmering Base Tunnel, Alternative Numeric Modelling of Long-term Rock Mass Behavior and Conceptual Support Design1309 At the construction Lot SBT 3.1 of the Semmering Base Tunnel long-term displacement increases caused an overutilization of the support measures over a length of approximately 100m behind the excavation face. It was concluded that these increases were caused by a strain softening of the rock mass. In numerical calculations visco-elastic and visco-plastic material models are used very often to model long-term rock mass behavior. In the present case a linear elastic – ideal plastic material model with a Mohr-Coulomb failure criterion in combination with a creep function was used to model long-term behavior. The strength and stiffness values as well as the creep values of the rock mass were identified based on a curve-fitting of monitored displacements to limit excavation interruptions due to testing of the rock mass and parameter identification for numerical modelling. Support measures and construction sequences for further excavation were designed based on the calculation results. | Long-Term Rock Mass Behavior, Semmering Base Tunnel, Numerical modelling, System Behavior
T15: Rock and rock mass propertiesSair KAHRAMAN (1), Ahmet Niyazi CANPOLAT (2), Mustafa FENER (3)1: Hacettepe University, Ankara, Türkiye; 2: General Directorate of Mineral Research and Explorations, Ankara, Türkiye; 3: Geological Engineering Department, Ankara University, Ankara, TürkiyePredicting strength loss of igneous rocks treated with microwave energy1310 This paper investigates the predictability of the strength loss of igneous rocks treated with microwave energy. First microwave treatment tests were performed at 6 kW power for the duration of 120s on the core samples of nine different igneous rocks such as granite, syenite and gabbro. Then uniaxial compressive strength (UCS) tests were carried out on the hot specimens. Mineralogical analysis, density and porosity tests were also performed on the samples. The data were evaluated using multiple regression analysis and an estimation equation with very high correlation coefficient was derived for the strength loss. The equation includes UCS, maximum surface temperature, quartz plus feldspar content and porosity values. The statistical test showed that the equation was valid. It was concluded that the derived equation could be used for the estimation of the strength loss of igneous rocks treated with microwave energy. | Igneous rocks, Microwave treatment, Strength loss, Regression analysis
T05: Digitalization & AutomatisationJukka-Pekka UUSITALO, Tobias WENDEL-EICHHOLZ, Matleena MELASAARISandvik Mining & Rock Solutions, FinlandUtilizing sensor technology in drilling optimization1313 Global climate goals have increased the need to reduce CO2 emissions and material waste in the mining industry. Rock drilling, being the first phase of the mining process, affects the whole chain from bedrock to crushed stone. Modern sensor technology provides a new level of visibility to the drilling process, enabling a reduction of CO2 emissions and material waste. Sandvik Mining and Rock Solutions is pioneering in this field of technology with the RockPulse® product. The product provides direct online stress wave measurement enabling fact-based adaptation to varying rock conditions and optimization of drilling parameters. RockPulse enables finding the optimal percussion power and the reduction of harmful stress waves, which increases the penetration rate and the effectiveness of rock drilling while reducing tool consumption. The RockPulse system has been verified to enable annual reductions of several tons of CO2 emissions per equipment. | climate goals, sensor technology, drilling optimization, rock knowledge
T13: Numerical methods in rock engineeringMun-Gyu KIM (1), Hyun-Jun PARK (1), Joo-Young OH (1), Chang-Heon SONG (1), Jung-Woo CHO (1), Ho-Young JEONG (2)1: KITECH (Korea Institute of Industrial Technology); 2: Pukyong National UniversityKinematic simulation of rock cutting performance of a 130t Roadheader in Korea1316 Roadheaders are being adopted to tunneling site in the South Korea because of the vibration issues of the conventional blasting method. Their tunnelling data for the Korean rocks has not been reported, Korean constructors are curious about the cutting performance of the machines. The study modelled the cutting head of 130 ton Roadheader and rock surfaces cut by it. The contacts between pick cutters and rock were defined by a kinematic software. A series of cutting operations (i.e., sumping and shearing processes) was simulated. Four classes of rock strength were considered as rock models. The cutting forces and torque was obtained from the simulation. The results showed that the torque level of current machine can penetrate up to the medium strength rock in the sumping process. In the shearing process, the cutting head can cut through up to hard rock. | Roadheader, cutting head model, Kinematic simulation, cutting force, torque
T13: Numerical methods in rock engineeringRui HUANG (1,2), Takafumi SEIKI (1), Qinxi DONG (3), Hui WANG (3), Ömer AYDAN (4)1: Utsunomiya University, Utsunomiya, Japan; 2: Xihua University, Chengdu, China; 3: Hainan University, Haikou, China; 4: University of the Ryukyus, Okinawa, JapanThe effective material properties of rock mass inversed from dynamic test data1317 In order to understand characteristics of wave propagation on rock mass, as well as to solve the difficulty of experiment result reproducibility at high frequency, it is essential to obtain the effective material property parameters of rock mass inversed from dynamic test data. In this study, the authors propose an inversing method based on dynamic finite element analysis (FEM) to obtain the elastic modulus and Rayleigh damping coefficients. This method is applied to in-situ experiments in an active Oya tuff underground quarry, Utsunomiya City, Tochigi Prefecture, Japan, and all material property parameters are determined using the displacement-time historical data integrated from the acceleration curves recorded at the sensor locations with impact loading. A good agreement of the dynamic numerical results using inversed material parameters compared with the measured acceleration data is obtained. | inversion, dynamic finite element analysis, elastic modulus, Rayleigh damping coefficients, in-situ experiment
T17: Rock slope engineeringZhibo JIA (1), Yan BAO (1), Lianjin TAO (1), Jin BIAN (2), Hu WEN (3), Haixiang ZHANG (3)1: The Key Laboratory of Urban Security and Disaster Engineering, Ministry of Education, Beijing University of Technology, Beijing, China; 2: College of Engineering, Guangdong Ocean University, Zhanjiang, China; 3: Beijing University of Technology, Beijing, ChinaSlope safety assessment based on dynamic anchor force1318 Anchor cable is widely used in rock slope reinforcement. In the design, the force of the anchor cable is often simplified as a constant load, which cannot reflect the deformation. To accurately evaluate the stability of the slope reinforced with anchor cables under earthquake load, the nonlinear mechanical model is introduced. Based on the Newmark method, the displacement formula is derived. The differences between the two models are compared under the framework of vulnerability. The results show that: 1) Deformation of anchor cables due to slope sliding. The anchor force is showing an increasing trend. 2) The stability of the slope is related to the ground motions. Vulnerability analysis can be used for quantitative analysis of slope safety. 3) The slope considering the change of anchor cable force has a greater probability of instability. Simplifying the anchor cable to constant loads may lead to an underestimation of the danger. | Anchor cable, Slope, displacement, Newmark, Earthquake
T15: Rock and rock mass propertiesMarte GUTIERREZ (1), Daisuke KATSUKI (1), Runar NYGRAARD (2)1: Colorado School of Mines, United States of America; 2: Oklahoma University, United States of AmericaShear failure and fracturing of horizontally layered shale1319 Understanding the mechanical behavior of shale formations is becoming increasingly important. Shales are essential in oil and gas production from tight unconventional resources. In geological carbon sequestration of CO2, shales typically form the caprock for geological storage. Fractures provide high permeability pathways for fluid flow and leakage for shales because of their low permeability. Shales have a layered structure with discontinuities parallel to the bedding plane, which can result in distinct anisotropy in their hydro-mechanical behavior. This paper aims to understand better the effects of intrinsic structural anisotropy from their layered structure on shale shear failure and fracturing behavior. Triaxial shear tests at constant confining stress were conducted on shale samples drilled horizontally parallel to the bedding plane. A new mechanism is proposed to explain the formation of shear/extensional fractures along bedding planes when shale samples are sheared under significant constant confining stress with the major principal stress perpendicular to the bedding plane. | Bedding planes, Layering, Shear Failure, Fracturing, Leakage
T06: Geological investigation and characterizationMarkus KASPAR, D. Scott KIEFFER, Qian LIUGraz University of Technology, Graz, AustriaHolographic mixed reality: an enhanced technology for visualizing and evaluating complex 3D geologic data1322 Rock mass characterization involves field data collection, processing, and analysis of the measurement results. Software packages facilitate creation of 3D models as well as the representation of rock mass parameters and resulting block arrays. The computer-generated imagery is traditionally illustrated as static perspective pseudo 3D screenshots, 2D maps or numerical tables and diagrams. Mixed reality greatly improves data visualization within an immersive and interactive 3D holographic environment enabling interaction with scaled holograms at the actual field dimension. The holograms are inspected individually or via remote collaboration within shared virtual spaces. The physical outcrop together with quantitative aspects of the rock mass structure is portrayed, enhancing communication and understanding of actual field attributes. This paper presents case examples of mixed reality holographic models based on photogrammetry, terrestrial and hand-held LiDAR devices. The benefits and potential applications of mixed reality in engineering geology and rock mass characterization are summarized. | Mixed reality, digitalization, rock mass characterization, hologram
T11: NATM versus TBMShengfeng HUANG, Misagh ESMAEILPOUR, Saadeldin MOSTAFA, Pooya DASTPAK, Rita SOUSAStevens Institute of Technology, United States of AmericaTBM penetration rate prediction using machine learning models and models’ generalization1323 Most existing models about penetration rate (PR) prediction have been developed and validated against data from one single project. This poses the question whether these models can perform well when faced with new data. We use two datasets of two tunnels built with the same construction method and in similar geological conditions. Different machine learning (ML) models are trained, validated, and tested with dataset from one tunnel and then generated to the other dataset. Additionally, the effect of several data processing techniques for splitting and scaling on the performance and generalization of the different models is tested. The results demonstrate that random forest (RF) and extreme gradient boosting (XGBoost) exhibit better performance than other models. Regarding generalization, CART and XGBooost model exhibit the best performance. The impact of splitting and scaling techniques on the generalization of the models becomes noticeable than on the performance of models. | Penetration rate, EPBM, Machine learning, Generalization, split and scale technique
T13: Numerical methods in rock engineeringHui HE, Chao WANG, Hua JIANG, Zhengyuan LIU, Zhiyong YANG, Yusheng JIANG, Jili FENGChina University of Mining and Technology Beijing, People's Republic of ChinaSimulation of ground deformation of subway station using pile-beam-arch method1324 The pile-beam-arch construction method is widely used in subway station engineering. However, the mechanical response of underground is not clear during the construction of using this method, particularly in subway station with asymmetric pilot tunnels layout. Taking one of the stations of Beijing subway line 17 as an example, the construction process is simulated by 3D FEM to reveal the mechanical response of the strata. Comparing the FEM prediction with monitoring data, the underground deformations at different construction phases are analyzed. The study shows that three construction stages consisting excavating pilot tunnels, primary lining and second lining greatly disturbed the strata. Comparing with the subway station with symmetrical pilot tunnels arrangement, the curves of surface settlement and the surface horizontal displacement generate a certain offset. The region affected by surface deformation is changed, which is benefit to the arrangement for monitoring points of surface displacement. | PBA method, Numerical simulation, Surface deformation, Asymmetry
T18: Early Career Forum (Young Researchers)Maria Teresa CARRIERO (1), Maria Rita MIGLIAZZA (1), Claudio SCAVIA (1), Leandro R. ALEJANO (2)1: Department of Structural, Building and Geotechnical Engineering, Politecnico di Torino, Italy; 2: Department of Natural Resources and Environmental Engineering, University of Vigo, SpainApplication of empirical rockfall classification methods to risk management in an Alpine valley road1326 Mountain secondary roads often follows complex land forms with high sub-vertical rock-cuts in outcropping rock prone to rock-fall events. Geo-structural rock mass surveys and collection of discontinuity data provide the basis for rock mass characterization and enable slope stability analysis and rock-fall hazard assessment. With this aim, a multiscale approach joining the non-contact techniques to the traditional one has been carried out focusing the rock cuts of a mountain road in Elva Valley (Piamonte, Italy). Based on collected data and the field visits, two different rock fall risk assessment empirical approaches were applied, namely the Rockfall Hazard Rating System (RHRS) and the so called Rockfall Risk Assessment for Quarries (ROFRAQ), adapted to road traffic. The application of these approaches to different road sections is demonstrated in the paper. Presented results will be the base to make risk management decisions and a discussion on results is eventually provided. | Rockfall, Risk assessment, RHRS method, ROFRAQ method
T04: Deep mining and tunnellingGilles ARMAND, Carlos PLUA, Minh-Ngoc VUAndra, France18 years of monitoring pore pressure evolution during and after excavation in the Callovo-Oxfordian claystone: the main insights1328 In France, the Callovo-Oxfordian claystone (COx) formation is considered as the host rock for the geological disposal for radioactive waste due to its very low hydraulic conductivity, low molecular diffusion, significant retention capacity and its self-sealing capacity. The hydromechanical behavior around underground openings in such claystone is also of importance for the short- and the long-term. At the short-term, the front advancement in “quasi-undrained” conditions modifies the stress field and create volumetric strains leading to pore pressure disturbance. If the effective stresses reach the failure criterion, the induced damage around these excavations might change the favorable properties of such formation. At the long-term, the geomechanical characteristics of the formation control the evolution of the induced fracture network and the time-dependent behavior around the openings which are key issues to design drift supports. This paper presents a comprehensive field monitoring study at two different scales conducted in the COx since 2004. | Callovo-Oxfordian claystone, hydromechanical behavior, mine-by-test, pore pressure
T01: Challenging rock engineering projectsRajanish RANJAN, Girish KALITANEEPCO, IndiaChallenges faced and mitigation measures adopted in construction of head race tunnel of Kameng hydro electric project (600 MW), Arunachal Pradesh, India1329 Kameng Hydro Electric project (4x150MW), a ROR scheme was constructed by North Eastern Electric Power Corporation Ltd in the West Kameng District of Arunachal Pradesh, India. This project lies in the Lesser Himalaya consisting of Precambrian and Gondwana rock formations. A 14.5 km long tunnel was constructed to convey water from Bichom to Kimi for 600 MW of power generation. This paper deals with the challenges faced during tunnel boring in tectonically disturbed Himalayan terrain and the mitigation measures adopted in overcoming these geological challenges. The challenges comprised cavity formation, blow out, Squeezing, high seepage and very weak rockmass with high rock cover. The mitigation measures adopted to overcome these challenges included fore-poling, umbrella/canopy with channel/joist and chemical/cement grouting etc. After overcoming all these tunnelling challenges, the boring of HRT was successfully completed in March’2015. | Mitigation, DRESS, Himalaya, Grouting, Squeezing, Weak rockmass
T07: Geological risks and natural hazardsRainer KIENREICH, Alexander KLUCKNER, Thomas MARCHERInstitute of Rock Mechanics and Tunnelling, Graz University of Technology, Graz, AustriaRock Fall Risk – Modular Risk Management Process1330 Rockfall is an alpine phenomenon and must be understood as a risk. Due to the large number of events, detailed geotechnical investigations are not possible in many cases. In this article, a processing workflow is presented that enables an evaluation of a natural rockfall trigger risk. The trigger risk as well as the extent of damage are categorized in a risk matrix. The study of 485 outcrops at several rock slopes shows that without groundwater influence, predominantly stable conditions exist; with groundwater, the stability drops by around 20 %. In the case of a risk value of the "high" class, individual case assessments are necessary; in the case of the "medium" classification, organizational measures are required to minimize liability. | Rockfall, risk management, trigger risk, liability
T06: Geological investigation and characterizationDae-Sung CHEON (1), Seungbeom CHOI (2), Won-Kyong SONG (1)1: Korea Institute of Geoscience and Mineral Resources, Republic of Korea (South Korea); 2: Korea Atomic Energy Research Institute, Republic of Korea (South Korea)Key Parameters and Distribution in Rock Mechanics for HLW Site Selection in Korea1331 A step-by-step approach is being adopted worldwide with respect to site selection for the geological disposal of high-level radioactive waste (HLW). Korea also adopted a three-step approach. In order to conduct systematic and efficient site investigation and site evaluation, a classification system for evaluation elements by stage has been proposed, and it is subdivided into aspects, items, and parameters. Among a total of 17 items and 103 parameters, rock engineering-related items are 3 items and 33 evaluation parameters. Uniaxial compressive strength, in-situ stress are selected as key evaluation parameters, taking into account domestic and foreign cases, the importance of rock engineering, and the existence of international standard testing methods. Their characteristics and the distribution range of the domestic parameters are investigated. In this study, two types of granite were selected and regional distribution characteristics were analyzed based on the data obtained through drilling up to 750 m. | HLW, Site investigation, Key parameters, Distribution, Uniaxial compressive strength, In-situ stress
T09: Long term behaviour of underground structuresJana JABER (1), Carlos PLUA (1), Minh-Ngoc VU (2), Gilles ARMAND (1), Jad ZGHONDI (1)1: Andra, Meuse/Haute-Marne Underground Research Laboratory, France; 2: Andra, Châtenay-Malabry, FranceEighteen years of feedback on the mechanical behavior of a 500m deep shaft on the Meuse/Haute-Marne (MHM) Andra’s URL (France)1335 Clay formations in their natural state exhibit very favourable conditions for the repository of radioactive waste. In France, the Callovo-Oxfordian claystone has been studied by Andra as a possible host rock for radioactive waste disposal since the 1990’s. In 2004, Andra began the construction of an underground research laboratory (called the MHM URL) in Bure, starting with shaft sinking operations (to a depth of 500 m). One of the shaft lining and surrounding rock was instrumented. Its concrete lining is highly monitored to understand its long-term behavior and the evolution of the loading due to the surrounding rock mass. Instrumentations were installed at -455 m, -467 m, -479 m, and -504 m depth. This paper presents the data collected over 18 years of monitoring. The outcome feedback consolidates the robustness of the shafts design forecast for the French Industrial Centre for Geological Disposal (Cigéo project). | Shaft sinking, deep excavation, lining monitoring, Callovo-Oxfordian claystone, geological radioactive waste disposal, Underground Research Laboratory
T16: Underground storage for liquid and gaseous mediaHippolyte DJIZANNE (1), Benoit BROUARD (2), Grégoire HÉVIN (3)1: INERIS, France; 2: Brouard Consulting; 3: StorengyMechanical stability of a salt cavern used for hydrogen storage1337 Underground salt cavern storage is recognised as one of the most suitable technologies to meet the challenges of the new European energy system. With the advantage of being mostly impermeable to gases, salt caverns are currently the only structures used to store hydrogen on a massive scale underground. This paper studies the consequences of a rapid withdrawal of hydrogen on the mechanical stability of a salt cavern. Gaseous hydrogen cooling could generate rock salt dilation, cavern closure and tensile stresses at the cavern wall. Numerical computations using the finite element method help to evaluate the geomechanical consequences of a rapid depressurisation in a selected cavern for an underground hydrogen storage demonstrator in France. | salt cavern, hydrogen, worst-case scenario, salt dilation, effective stress
T15: Rock and rock mass propertiesVladimir FRIDSami Shamoon College of Engineering‎, IsraelEffect of rock stiffness change on acoustic emission1338 It is known that the ratio of rock stiffness around the mine workings and the stiffness of the ‎surrounding strata has a crucial meaning for rock stability in the close vicinity of the ‎underground excavation. Significant resources were invested for the research aiming to ‎understand the failure mechanism using acoustic emission (AE) to evaluate the relationship ‎between the parameters of AE and crack/fracture dimension/scale to determine statistical ‎regularity of AE appearance before oncoming rock collapse and features of acoustic wave ‎attenuation during its propagation via rock massive. However, the methodology of the ‎rock stiffness assessments based on the AE parameters is still lacking. The paper considers the physical basis for applying AE for stiffness assessment ‎in underground conditions. | acoustic emission, rockburst, rock stiffness
T07: Geological risks and natural hazardsJian HUANG, Jingqing YUAN, Jianhong LIAOState Key Laboratory of Geohazard Prevention and Geoenvironment Protection, People's Republic of ChinaNumerical analysis of rockfall fragmentation mechanism1339 Fragmental rockfall is one kind of common geological disaster in mountainous areas. In this paper， the discrete element method, particle flow code (PFC) is used to simulate the impact and fracture process of rock mass， analysis the impact process of rock mass at different falling heights and impact angles， and the variation trend of impact force， velocity and the number of cracks in the rock mass. The results show that the velocity of rock mass decreases sharply and the crack develops rapidly after impact on the slope. With the increase in falling height， the rock mass velocity changes in a "second step shape"， and the number of broken blocks increases while decreasing the rock mass size. With the increase of slope angle， the "double peak phenomenon" of impact force becomes less obvious. The results provide a theoretical basis for the numerical simulation of fragmental rockfall and hazard assessment. | fragmental rockfall; PFC; impact angle; impact force
T14: Petroleum engineering and carbon sequestrationPengwei ZHANG, Huantong LIU, Lili LI, Baoguo LIUBeijing Jiaotong University, Beijing, ChinaFaults reactivation risk evaluation during water injection into shale gas reservoirs: A case study1343 Hydraulic fracturing is an effective technique for shale gas development, which breaks tight shale by injecting a large amount of fracturing fluid under high pressure. The potential impacts of hydraulic fracturing on the surrounding environments (such as hydraulic fracturing induced earthquakes) have aroused extensive attentions. Hence it is necessary to study on the evolution rules of reservoir in-situ stress and fault stability during the water injection process of hydraulic fracturing. In this work, a three-dimensional geomechanical model of a shale gas reservoir which located in Southwestern China is established firstly; Based on the in-situ stress field, numerical simulations on the influence of local in-situ stress and fault stability during quasi-dynamic and dynamic water injection are made. With the calculated shear strain distribution, a workflow for evaluating the seismic moment response in the fault region during water injection is proposed. | shale gas, geomechanics, pore pressure, in-situ stress field, fault stability
T15: Rock and rock mass propertiesMin GAO, Xu ZHU, Chengguo ZHANG, Joung OHUniversity of New South Wales, AustraliaA modification of nonlinear Forchheimer’s coefficient for fracture flow during shear1346 This study introduces a new hydromechanical model to estimate both shear and nonlinear flow behaviours of a single rock fracture, taking into account the effects of fracture surface morphology on the fracture flow behaviours. The model incorporates a multi-scale roughness shear constitutive model that considers the adhesion and abrasion wear theories to predict the shear behaviours of a fracture due to shear deformations. The fracture permeability is estimated using the Forchheimer-based equation, which accounts for the combined effects of the fracture void spaces, aperture distributions, and fluid flow tortuosity. Laboratory shear-flow experiments under different hydraulic pressures and normal loading conditions are conducted to validate the proposed model. The model is in good agreement with experimental data and can be applied to sheared aquifers. | Shear-flow model, single fracture, surface roughness, multi-scale roughness, nonlinear flow
T18: Early Career Forum (Young Researchers)Anastasios TSIKRIKIS (1), Vassilis MARINOS (2), Theodosios PAPALIANGAS (1)1: Department of Environmental Engineering, Hellenic International University, Thermi, Greece; 2: Department of Civil Engineering, National Technical University of Athens, GreeceA study on the correlation between Hoek–Brown mi constant and Brinell hardness of intact rocks1347 Conventional triaxial compression tests were conducted on dry cylindrical samples of three silicate and three carbonate rocks with porosities in the range 0.3%-24.0%, and confining pressures 0-70 MPa, in order to determine the constant mi of the Hoek-Brown criterion for intact rock. The same rock types were used to determine the Brinell hardness number (BHN) using a spherical indenter with 10 mm diameter and a vertical indentation force of 500 kgf. The values of BHN ranged from 8 to 150 and those of mi from 5 to 24. The experimental results show that the constant mi increases linearly with Brinell hardness and that both BHN and constant mi depend on mineralogy and porosity. The results may be proved useful in estimating the Hoek-Brown mi constant from Brinell hardness which can be determined using small and easily prepared rock samples and sufficiently compact and easy to operate indentation testers. | constant mi, Brinell hardness, triaxial tests, Hoek-Brown criterion, porosity
T15: Rock and rock mass propertiesGreg GAMBINO (1), John P. HARRISON (2)1: University of Toronto, Canada (now at WSP Canada Inc.); 2: University of Toronto, CanadaTemperature-dependent strength of ice-filled discontinuities in frozen and thawing rock masses1350 This paper presents new results regarding the strength of ice-filled discontinuities. Careful laboratory testing using prepared core specimens containing ice in artificial discontinuities allowed the indirect tensile strength of ice-rock interfaces to be determined at different temperatures. These results were combined with those for shear strength published by others in 2000, to extend the shear strength data into the tensile regime. The combined results suggest a linear Coulomb criterion with no tensile cut‑off is appropriate for both the shear and tensile regimes at −2.5 and −5.0°C. Two regression models were investigated, one extending the shear data into the tensile regime, and the second combining the indirect tensile and shear data with the shear data being used to inform the relation through Bayes’ rule. These analyses confirm the robustness of the indirect tensile testing and provide a predictive strength criterion for rock engineering design in frozen and thawing discontinuous rock masses. | ice-filled discontinuities, tensile strength, strength criterion, Bayesian regression
T05: Digitalization & AutomatisationAdrián J. RIQUELME (1), José Luis PASTOR (1), Miguel CANO (1), Roberto TOMÁS (1), Antonio ABELLÁN (2)1: University of Alicante, Spain; 2: Centre de recherche sur l’environnement alpin (CREALP)Influence of SfM reconstruction techniques on the extraction of rock slope discontinuities1351 Rock slope discontinuities can be analyzed using 3D point clouds (3DPC), which are typically acquired through 3D laser scanning (3DLS) instruments or Structure from Motion (SfM) photogrammetry. While 3DLS is often regarded as a precise dataset, the use of SfM is gaining popularity due to the advent of remotely piloted aircraft systems and its relative affordability. Traditionally, extracting discontinuities from 3DPC relies on dense cloud reconstruction. However, the exploration of tiled models as an alternative approach remains limited. In order to assess the viability of using tiled models, we conducted an experiment on a pyramid-shaped sculpture reconstructed using both 3DLS and SfM techniques. The results demonstrate that the orientation of discontinuities obtained from the tiled model aligns well with those derived from both the TLS and dense cloud results. Interestingly, the extraction of discontinuities from the tiled model proves to be more efficient than from the SfM dense cloud. | Structure-from-Motion, 3D Point Clouds, discontinuities, rock slope, experiment, tiled-model
T15: Rock and rock mass propertiesNatália de Faria SILVA, Eduardo Antonio Gomes MARQUES, Carolina Crissafe dos Santos LEMOS, Carolina de Souza Pires COSTAUniversidade Federal de Viçosa, BrazilProposition of an accelerated cycling procedure for rocks with low porosity1352 A relevant method for study weatherability of rocks is the accelerated alteration simulation which intends to describe susceptibility to weathering and its products. Nevertheless, it can be difficult to set which methodology should be adopted, as the initial state of sample must be reconciled with the environment to which it’ll be exposed, so that, in experimental time scale, it’s feasible to observe aspects of increasing alteration and modification in properties. In a weatherability study of a metamorphosed hydrothermalized basalt with very low initial porosity, an accelerated cycling throughout immersion in sodium sulfate was adopted. Even subjecting the rock to 100 cycles, samples have only shown signs of no significant modification of physical properties. To produce substantial weathering change, a much larger number of cycles would be required, so some modifications to the test procedure are proposed, allowing the execution of a greater number of cycles without increase in duration of the experiment. | Weatherability, weathering, accelerated cycling, alteration simulation
T09: Long term behaviour of underground structuresTilman SANDNER, Claas MEIER, Boley CONRADBoley Geotechnik GmbH, GermanyRehabilitation of old masonry tunnels – challenges and possibilities1353 The Reicholzheim tunnel on the single-track line 4920 from Lauda to Wertheim had to be rehabilitated, since the existing tunnel lining, made of mortar sandstone blocks, is in a structurally poor condition. To rehabilitate the tunnel, the existing masonry shell was reinforced with a self-supporting reinforced concrete inner shell. The low clearance profile required partial removal of the masonry. Due to the vibration-sensitive structure and high rock strength, the milling work had to be carried out on the basis of a separate safety concept including high-pressure water cutting. To secure unstable areas of the vault, CFRP safety devices were installed. Due to the partly non-existent back-fill and the narrow time window during night-time closures, special requirements were placed on the concreting. As the responsible design-review-engineer, the design and compliance with the railroad regulations with regard to the innovative safety and rehabilitation measures were also challenging. | Tunnel rehabilitation, masonry shell, sandstone, CFRP safety devices, railroad regulations
T13: Numerical methods in rock engineeringMasoud TORKAN (1), Amir HOSSEINI KHORASGANI (2), Lauri UOTINEN (1), Alireza BAGHBANAN (2), Mikael RINNE (1)1: Department of Civil engineering, Aalto University, Finland; 2: Department of Mining Engineering, Isfahan University of Technology, Isfahan, IranInfluence of contact shape and distribution on fluid flow through a fracture1355 Fluid flow through a rough fracture can be affected by several geometrical parameters such as aperture, roughness, and contact area. Of these, eddy flow can occur around contact areas and change streamline patterns. Fluid flow behavior through a 10 cm × 10 cm square fracture was numerically analyzed with different contact shapes and distributions. The basic shape of the contact area is assumed to be square with a 1 cm2 area. The squares as contact areas through fractures were distorted with different ratios, rotations, and relocations. The total contact area and the physical aperture in all models were 25 cm2 and 1 mm, respectively. The flow rates through the fractures were computed with 5 different water pressures. The Forchheimer equation was adopted to analyze results. The calculations highlight the importance of the parameter β in the Forchheimer equation, which reflects the impact of fracture surface geometry on fluid flow. | fluid flow, contact area, hydraulic aperture, numerical modeling
T05: Digitalization & AutomatisationAndreas-Nizar GRANITZER (1), Franz TSCHUCHNIGG (1), Wolfgang SUMMERER (2)1: Graz University of Technology, Graz, Austria; 2: ILF Consulting Engineers Austria GmbH, Rum b. Innsbruck, AustriaIntegration of Point Cloud Data for Numerical Simulations Using NURBS Surfaces1356 The numerical modelling of complex surface geometries represents a challenging task in computational geotechnics. Corresponding problem classes include non-horizontal topographic surfaces (TS) in mountainous terrain, rock mass discontinuities or steep slopes, presumably inducing significant stress redistributions in the project domain that need to be considered. This raises an obvious question at the interface with geographic information systems: How to integrate point-based surveying measurements defining the TS into the numerical modelling process? In this respect, we present a step-by-step methodology based on survey data from two infrastructure projects in Austria, at the core of which NURBS surfaces are used to generate TS models with high accuracy. | NURBS, GIS-to-FEM, point pattern analysis, optimal tunnel route, topographic surface
T04: Deep mining and tunnellingKrzysztof FUŁAWKA, Piotr MERTUSZKA, Marcin SZUMNY, Lech STOLECKI, Izabela JAŚKIEWICZ-PROĆKGHM CUPRUM Ltd. R&D CentreNovel method of multi-face destress blasting efficiency assessment1359 In this paper, the newly formulated solution of multi-face destress blasting efficiency assessment is presented. The developed method is relevant for near and far-field effect evaluation and is improved by the duration, amplitude, and frequency characteristics of blast-induced seismic waves. The proposed approach is based on the advanced analyses of the waveforms generated by blasting, ground motion prediction equations and data describing the technological parameters of blasting in terms of the amount of explosives, delay times, and spatial location of mining faces. The proposed solution was validated in deep underground mines in Poland in which the room-and-pillar mining method is applied. Based on the performed analysis, it is shown that a new method may be used as an element of rockburst hazard control in underground mines. However, the developed method may also be successfully implemented in other engineering practices, including open pits and quarries. | Destress blasting, seismic waves, blasting efficiency, mining seismology, underground mining
T01: Challenging rock engineering projectsGuangming YU (1), Penghui ZHANG (1), Qimeng SHI (1), Guanwen LIANG (1), Jun LEI (2), Xinwang YANG (1), Lijun KUANG (2), Daning WANG (3), Mikhail D. KOVALENKO (4), Irina V. MENSHOVA (5), Alexander P. KERZHAEV (6)1: Civil engineering College, School of Civil Eengineering Qingdao University of Technology; 2: China Construction Fifth Engineering Division Corp.,ltd; 3: regio iT gesellschaft für informationstechnologie mbh; 4: Institute of Applied Mechanics, Russian Academy of Sciences; 5: Institute of Earthquake Prediction Theory and Mathematical Geophysics; 6: Bauman Moscow State Technical UniversityThe Synergetic Evaluation Model of Machine-Rock in TBM-EPB Shield Construction and its computer realization1361 This paper explores the influencing factors, mechanical mechanism and evaluation model of "machine-rock" cooperative mapping in dual-mode shield (TBM-EPB) tunnel construction, and scientifically determines the order parameters of artificial and natural interaction system evolution in dual-mode shield (TBM-EPB) tunnel construction by means of mechanics and Synergetics, and establishes a "machine-rock" cooperative mapping evaluation model for dual-mode shield (TBM-EPB) tunnel construction. The "machine-rock" cooperative mapping of dual-mode shield (TBM-EPB) tunnel construction is evaluated by computer, and verified by a typical case of efficient and safe construction of dual-mode shield (TBM-EPB) tunnel between Liuxiandong Station and Baimang Station of Shenzhen Metro Line 13. Finally, the future development trend and key technologies of dual-mode shield (TBM-EPB) tunnel construction are predicted, and the future research trends. The results of this paper have important guiding significance for the toughening construction of underground tunnel and its cooperative coexistence with the environment. | dual mode shield (TBM-EPB), tunnel construction, "machine-rock" interaction, collaborative mapping, evaluation
T12: New developments in rock supportConrad BOLEY (1), Paul PRATTER (2), Lisa WILFING (2)1: Institute for Soil Mechanics and Geotechnical Engineering, Bundeswehr University Munich, Germany; 2: Boley Geotechnik GmbH, Munich, GermanyResearch of safety-relevant natural and structural factors influencing the load-bearing capacity of rock stabilization with chemical grouts1362 Geotechnical structures are subject to environmental and structural factors depending on formation water or the rock fracture degree. These factors inevitably affect the load-bearing capacity of the structure and in consequence the stability. Due to increasingly dense development, space constraints and the relocation of buildings to the underground, the subsoil improvement is playing an increasingly important role, as this often means that the subsoil has to adapt to the necessary requirements of the structure and not vice versa. The research focuses on the stabilization of rock with different high performance chemical grouts. For this purpose, the rock mechanical testing program on grouted rock was extended by special tests to investigate the material behavior of the chemical grout and its bonding with the surrounding rock in detail. The results of the research work are of safety-relevant importance and should therefore already be considered in the design phase of a construction project. | Rock stabilization, chemical grout, formation water, rock fracture
T13: Numerical methods in rock engineeringMiguel Angel MÁNICA (2), Antonio GENS (1), Jean VAUNAT (1), Gilles ARMAND (3), Minh-ngoc VU (3)1: Universitat Politecnica de Catalunya - CIMNE, Spain; 2: National Autonomous University of Mexico. Mexico; 3: ANDRA R&D, FranceAnisotropy Effects on the Response of Deep Tunnels Excavated in Claystone1364 Tunnelling in argillaceous rock is very common because of the widespread occurrence of those materials in the earth crust. Research on argillaceous rocks have been further stimulated in recent times because of their suitability as host rocks in deep geological repositories for radioactive waste. The paper presents a numerical analysis, using an especially developed constitutive model for argillaceous rocks, that reproduces successfully the observations obtained in the excavation of tunnels in Callovo-Oxfordian claystone at the Meuse/Haute-Marne underground laboratory. Particular attention is given to the configuration of the fractured zone and its dependence on the orientation of the tunnel. Using this analysis as reference, the effects of stiffness and strength anisotropy as well as of the in-situ stress anisotropy are examined. The analyses reveal that either strength anisotropy or the initial in-situ stress state have a dominant influence depending on the alignment of the tunnel. | anisotropy, tunnels, claystone, fractured zone, numerical modelling, in-situ stresses
T14: Petroleum engineering and carbon sequestrationGuodong CHENG (1), Xueyu PANG (1), Zhengsong QIU (1), Jiankun QIN (1), Ning LI (2)1: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, People's Republic of China; 2: Oil and Gas Engineering Research Institute (Tarim oilfield Company), China National Petroleum Corporation, Tarim, People's Republic of ChinaWell Cement Composition Optimization for Deep Well Applications1367 Recent studies had revealed that traditional high-temperature resistant silica-enriched well cements are not suitable for deep well cementing applications due to strength retrogression problems in the long term. This study investigated the use of new admixtures, including fly ash and ground blast furnace slag (GBFS), to mitigate such strength retrogression issue of cement. The combined use of GBFS and silica at optimized dosages effectively prevented well cement strength retrogression up to 30d, but strength reduction and permeability increase were still observed from 30d to 90d. On the other hand, the combined use of fly ash and silica effectively prevented both strength reduction and permeability increase of the well cement. However, the addition of fly ash increased the consistency of cement slurry significantly, making it difficult to pump. Finally, the slurries prepared with mixtures of well cement, silica flour, fly ash, and GBFS exhibited both excellent flowability and long-term strength stability. | Fly ash; Granulated Blast Furnace Slag; Silica-enriched well cement; long-term strength retrogression; ultra-high temperature
T01: Challenging rock engineering projectsVerya NASRIAECOM, New York, United States of AmericaDesign and Construction of the Montreal Largest Transit System1368 Once completed, the Montreal Réseau Express Métropolitain (REM) will be the fourth largest automated transportation system in the world. The REM represents the largest transportation infrastructure in the region since the Montreal metro inaugurated in 1966. The proposed solution fosters environmentally sustainable transportation and represents a construction cost of approximately 7.0 billion Canadian dollars. The project consists of 67 km over four branches of twin track and includes 26 stations with 3 underground stations in downtown Montreal. One of the underground stations was built using the NATM method with thin permanent shotcrete initial and final liners separated by a sprayed on waterproofing membrane. The project also includes the rehabilitation and enlargement of the 100-year-old double track Mont Royal Tunnel which is about 5 km long. The REM also consists of 3.6 km new TBM tunnel connecting downtown to the Montreal International Airport through saturated soft ground and karstic rock. | TBM Tunnel, NATM Station, Deep Shaft, Tunnel Rehabilitation, Shotcrete Permanent Liner
T13: Numerical methods in rock engineeringJiwoo AHN (1), Jurij KARLOVŠEK (2), Adrian SMITH (3)1: BHP, Australia; 2: The University of Queensland, Australia; 3: PSM, AustraliaProbabilistic assessment of rock loads for tunnel support design1370 The stability of tunnels through relatively hard rock and low stress environments are typically governed by loosening loads. These are typically caused by unstable blocks bound by discontinuities in the rock mass. There are numerous methods to determine the support pressure required to resist these loads. However, current approaches do not explicitly consider the likelihood of occurrence of such loads. This paper proposes a methodology using binomial probability theory to incorporate the likelihood of a given rock load and calculate the corresponding probability of exceedance. The determination of a probability of exceedance for tunnel support allows for a quantitative assessment of the risk associated with a design. An application of this method is presented with the use of a discrete fracture network (DFN), and the Cross River Rail project in Australia as a case study. | Tunnelling, Support design, Rock loads, Probability, Discrete fracture network
T07: Geological risks and natural hazardsLianjin TAO, Zhigang WANG, Zhibo JIABeijing University of Technology, People's Republic of ChinaFailure mechanism of the utility tunnel with flexible joints under reverse fault dislocation1371 The earthquake-damaged investigation found that tunnel structures crossed the active fault zone, and its affected area suffered the most severe damage. Through model tests and numerical simulations, the paper reveals the failure mechanism of the utility tunnel structure with flexible joints across the active fault zone. The results show that the damage range of the utility tunnel structure with flexible joints in the hanging wall is significantly larger than that of the footwall. The damage range is 2.5D and 1.25D, respectively. The utility tunnel structure is prone to stress concentration and damage in the corner area. The damage degree of the lining structure is classified according to the tensile damage factors, namely, no damage, slight damage, moderate damage, and severe damage. Combining the large deformation of flexible joints can effectively improve the design of tunnel structures across the fault zones and improve the seismic performance of tunnel structures. | Reverse fault; Utility tunnel; Flexible joint; Model test; Numercial simulation; mechanical response
T03: Deep geothermal energyShuai FENG (1), Weiren LIN (1), Susumu SHIBUTANI (2), Terasu SANO (3), Nana KAMIYA (4)1: Graduate School of Engineering, Kyoto University; 2: Chi-ken Sogo Consultants Co., Ltd; 3: Daigas Gas and Power Solution Co., Ltd; 4: Doshisha UniversityCorrelations between thermal properties and elastic wave velocities of volcanic rocks1372 Thermal properties such as thermal conductivity are necessary to understand the subsurface thermal structure. It remains difficult to obtain such thermal properties without laboratory measurement on rock core samples, while such core samples are usually difficult to obtain especially at great depths. This research seeks to derive an empirical equation between thermal properties and elastic wave velocities by analysing laboratory measurement data on volcanic rock core samples. Measurements of thermal properties and elastic wave velocity have been conducted on volcanic rock core samples collected from Aso volcanic region, Japan. And correlations between measured physical properties have been discussed. Both thermal conductivity and P-wave velocity were found to decrease with increasing porosity. And thermal conductivity presented a tendency to increase as P-wave velocity increased, while an acceptable empirical equation failed to be obtained which indicated the need for further research. | Thermal properties, elastic wave velocity, volcanic rocks, Aso volcanic area
T17: Rock slope engineeringJavier GONZÁLEZ-GALLEGO, José ESTAIRE, María SANTANACEDEX, SpainUse of representative values of geometrical properties of discontinuities in rock slope verifications according to EC71375 This work aims to obtain representative values for the geometrical properties of families of discontinuities, within the criteria set out in the final draft of Eurocode 7 (EC7), by a conservative estimation of the mean value and not as a purely average value, as it is done for the rest of the geotechnical properties. This paper describes how to use the EC7 methodology to obtain representative values for the geometrical properties of discontinuities. Moreover, an example is included to compare the safety factor of a wedge using this EC7 methodology and the derived from normal practice. This example deals with a typical issue where the data collection is done manually and the number of values is small. With the results obtained, some questions arise as to what should be the correct way to obtain a representative value for the case of wedges in rock. | Geometrical properties, Eurocode, rock slope stability
T15: Rock and rock mass propertiesJohn William de Bradnee MARTIN (1), Alexander KLUCKNER (1), Gerold LENZ (2), Thomas MARCHER (1)1: Institute of Rock Mechanics and Tunnelling, Graz University of Technology, Graz, Austria; 2: iC consulenten ZT GesmbH, AustriaBack-analysis of rock mass parameters at the Semmering Base Tunnel based on the convergence confinement method1376 The monitoring of geodetic targets installed at the tunnel lining provides reliable information on the system behaviour. At the Semmering Base Tunnel (SBT), engineers use the software package TUNNEL:Monitor to visualise monitored displacements and to make short-term predictions ahead of the face. A toolbox to apply the convergence confinement method (CCM) to the geodetic measurements has been incorporated into TUNNEL:Monitor for the purpose of back-analysing rock mass parameters post tunnel construction. This paper details the results of two case histories undertaken to assess the suitability of the back-analysis procedure implemented in TUNNEL:Monitor. Findings from the case studies confirm TUNNEL:Monitor is suitable for the back-analysis of rock mass parameters, provided the limitations associated with the procedure are well understood and the procedure is not extended beyond its applicability. | TUNNEL:Monitor, Semmering Base Tunnel, back-analysis, displacement monitoring, convergence confinement method, anisotropy
T07: Geological risks and natural hazardsOlivier BUZZI, Davide GUCCIONEPriority Research Centre for Geotechnical Science and Engineering, The University of Newcastle, AustraliaEffect of shape on the survival probability of rock replicas during free fall tests1378 Fragmentation of rocks upon impact is a complex phenomenon that is not well understood. The first question to answer to adequately model fragmentation is whether a falling block is likely to fragment at impact or not. This question can be answered if the survival probability of the rock is known, but this is not trivial as no model or method exists to predict the survival probability of natural rocks. The authors have recently developed a model that can predict the survival probability of brittle rocks under collinear impact, following a preliminary breakthrough for brittle spheres. One complexity associated with irregularly shaped rocks is the possibility of non-collinear or eccentric impacts. The objective of this study is to conduct drop tests on irregularly shaped rocks and highlight the significance of collinear and eccentric impacts on the survival probability in drop tests. | Rockfall, Fragmentation, Shape, Survival Probability, Collinear, Eccentric
T17: Rock slope engineeringClarence BUTCHER (1), Olivier BUZZI (1), Anna GIACOMINI (1), Robert BERTUZZI (2), Vaughan GRIFFITHS (3)1: The University of Newcastle, Australia; 2: PSM, Engineering Consultants; 3: Colorado School of Mines, U.S.A.Capturing the roughness of discontinuity traces in the field with high accuracy: the effect of photograph resolution1379 The recently developed stochastic approach to discontinuity shear strength (StADSS) avoids scale effects by predicting peak and residual shear strength using full scale discontinuity data. StADSS has been applied to mortar replicas of perfectly matched specimens in the laboratory, but application to large in situ discontinuities is yet to be undertaken. Paramount to the in-situ application of StADSS is the adequate collection of discontinuity roughness information. This paper presents an approach to digitize the seed trace of in-situ discontinuities. Several identical images of a seed trace with varying pixel densities were analyzed to determine what pixel to millimeter ratio was sufficient to enable a Gaussian distribution of gradients to develop. It was found that a pixel density of 6-7 pixels per millimeter of seed trace length was sufficient to develop the parameters of a suitable Gaussian distribution of gradients, which could then be used for further statistical analysis. | Discontinuity, Roughness, Scale Effect, Shear Strength
T05: Digitalization & AutomatisationMyung-Kyu SONG (1), Hyun-Koo LEE (1,2), Jae-Kyum LEE (1), Sean Seungwon LEE (1)1: Hanyang University, Republic of Korea (South Korea); 2: AICONT, Republich of Korea (South Korea)Identification of the optimal time series machine learning algorithm for the prediction of the ground subsidence with TBM machine data1380 Controlling ground settlement during tunnel excavation in urban areas is a challenging task for contractors even with tight and comprehensive monitoring. In this study, utilizing the settlement monitoring and the sensor data collected during TBM drive, penetration and settlement prediction models are built. We postulated that TBM machine sensors may capture both actions of the machine and the reactions of the ground. Hence the prediction of settlement can be made if an appropriate algorithm is applied. There are a few sequential algorithms such as vanilla LSTM, LSTM with attention, Transformer, and Informer. This paper attempts to identify the optimal algorithm for training sensor data with a sub-workstation equipped in TBM. By comparing the performances of the algorithms, the DALSTM is identified as optimal algorithm for TBM machine data. Furthermore, subsequent analyses are carried out to develop a settlement prediction model, which demonstrates exceptional performance, marking a promising step towards deployment of the proposed method. | TBM, Subsidence Prediction, Machine Learning, Time Series, Sensor Data
T06: Geological investigation and characterizationLeandro R. ALEJANO (1), Elena MARTÍN (1), Ignacio PÉREZ-REY (1), Brais X. CURRÁS-REFOJOS (2), Fco. Javier SÁNCHEZ-PALENCIA (2)1: University of Vigo, Spain; 2: CSIC-CCHS - Instituto de Historia, Madrid, SpainRoman gold exploitation at the archeological site of Las Médulas (NW-Spain) by means of Ruina Montium: a rock and fluid mechanics perspective1383 Las Médulas is an area located in NW-Spain featuring a landscape environment formed by an old Roman gold mining operation. It is thought to be the largest open-pit gold mine in the Roman Empire and it was exploited during I and II centuries AD. The archaeological site and its environment were declared UNESCO World Heritage in 1997, based on its value as a cultural landscape. The most spectacular mining system used there was the one that Pliny the Elder called “Ruina Montium”, that is, "the collapse of the mountains". This technique was applied to reach in one go the conglomerate levels richer in gold (Santalla formation), removing a thick cover of conglomerate block-in-matrix (bimrock) type waste. Unfortunately, there are no obvious remains of this procedure. In this multidisciplinary study in progress, archaeologists and engineers work together to better understand the detailed process used by the Romans to cave the mountains. | Roman mining, archaeology, fluid mechanics, rock mechanics, collapse, bimrock
T15: Rock and rock mass propertiesMauro MUÑIZ-MENÉNDEZ (1), Ignacio PÉREZ-REY (2)1: CEDEX, Madrid, Spain; 2: University of Vigo, Vigo, SpainInfluence of the specimen slenderness on the direct tensile strength of rocks1384 Some rock engineering design operations are mainly controlled by the tensile strength and deformability of the rock (i.e., critical span of excavations or hydraulic fracturing). The ISRM Commission on Testing Methods and the ASTM procedures recommend the use of cylindrical rock specimens, with height-to-diameter (H/D) ratio of 2.5 to 3.0 for direct tensile strength (DTS) determination, in a similar way as per UCS testing. Nevertheless, it is unclear how this ratio may affect the tensile strength of a rock when directly determined. In the present work, the authors performed some series of numerical simulations with a 3D distinct element code (3DEC), replicating DTS tests carried out on specimens presenting five H/D ratios (0.5, 1, 1.5, 2, 2.5, and 3). The study is complemented with laboratory DTS tests in granite. The results herein presented indicate that H/D ratios greater than one have almost negligible influence on DTS. | direct tensile strength, slenderness, suggested method, 3DEC
T07: Geological risks and natural hazardsMuriel GASC-BARBIER (1), Véronique MERRIEN-SOUKATCHOFF (2), Jean-Luc GENOIS (1), Charly MOUGIN (1), Pierre AZÉMARD (1)1: cerema, France; 2: le Cnam, France10 years of thermo-mechanical monitoring of rock columns - les chandelles de l’Escalette, France1385 Rock instabilities can represent major risks for local populations depending on their geographical location. Even if different factors such as precipitation, seismic activity and freezing, are known to trigger rockfalls it is more and more assumed that thermal cycling have a role in cracking initiation or propagation. Here we use data of the first six years of field monitoring of a 50-meter-high French dolomitic cliff, located above an important highway in the south of France (A75) to support this thinking. Evolution of the aperture of joints and temperature were followed on ten different locations around les Chandelles de l’Escalette. Results will be discussed in terms of mechanical response to temperature variations. | Thermomechanics, rock columns, monitoring, propagation, failure
T12: New developments in rock supportMathias LAURAEUS (1,3), Mikael RINNE (1), Antti LAUKKANEN (2)1: Department of Civil Engineering, Aalto University, Espoo, Finland; 2: Betulium Ltd, Espoo, Finland; 3: Sweco Finland Ltd, Helsinki, FinlandMicrofibrillated cellulose as additive for wet-mix shotcrete1386 Shotcrete is a widely used rock reinforcement method that significantly impacts the carbon footprint of underground construction and mining. The sustainability of shotcrete can be improved by, e.g., replacing a portion of cement in the mix with low-carbon materials or minimizing shotcrete rebound by increasing the plastic yield stress of fresh shotcrete. A microfibrillated cellulose (MFC) has recently drawn interest from the shotcrete industry due to its potential for improving the sustainability and cost-efficiency of shotcrete. The MFC is low-carbon footprint material that has rheology-modifying effects on aqueous systems, such as shear thinning behavior and high zero-shear viscosity. In this study, a preliminary investigation of the benefits of MFC in shotcrete application was done through a series of laboratory tests. Results indicate that the MFC improves the immediate stiffness of accelerated shotcrete, and other essential performance factors are not significantly affected. | Microfibrillated cellulose, shotcrete, additives, carbon footprint, rebound
T13: Numerical methods in rock engineeringTaehyun KIM (1), Chan-Hee PARK (2), Changsoo LEE (1), Jin-Seop KIM (1)1: Korea Atomic Energy Research Institute, Republic of Korea (South Korea); 2: Korea Institute of Geoscience and Mineral Resources, Republic of Korea (South Korea)Numerical simulation of THM coupled behavior in the high-level radioactive waste disposal using OGS-FLAC1387 Geological disposal of high-level radioactive waste (HLW) is considered the most feasible way to isolate waste from the sphere of human life. It is essential to predict the coupled thermo-hydro-mechanical-chemical (THMC) effect on the disposal system under the deep depth condition to secure the safety of the disposal system. Especially numerical simulation is an effective method for evaluating long-term behavior. We performed a series of numerical simulations to model the THM coupled behavior of the Full-scale Emplacement (FE) experiment as a part of Task C in the DECOVALEX-2023 project. We compared the numerical simulation results using OGS-FLAC to the field data, including pore pressure, relative humidity, temperature, displacement, and stress at the bentonite and host rock, considering the ventilation process. The capillary pressure was the dominant factor in the flow of the buffer system, and we observed thermal-induced pressurization in the far-field host rock. | THM coupled behavior, FE experiment, DECOVALEX, OGS-FLAC
T12: New developments in rock supportFei ZHAO, Zhenming SHI, Songbo YUDepartment of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai, People's Republic of ChinaResearch on application of new combined support structures in reinforcing rocky slopes containing weak interlayers1388 Anti-sliding piles have good reinforcement effect in slope under earthquake. In this study, new combined piles are proposed, and models of bedding rocky slopes with different weak interlayers are established. The force characteristics, reinforcement mechanism and effect of the combined piles are analyzed. The main findings are as follows: the different mechanical mechanisms of the slope reinforced by the flexible and rigid combination of piles result in different deformation patterns; through the pre-stress of the horizontal connection structure, the h-shaped flexible structure connecting the double-row piles can reasonably distribute the squeezing pressure and shear force on the piles to realize the synergistic seismic resistance of the piles, and its reinforcement effect is better than other piles. Based on the above findings, the study of combined piles for reinforcing rocky slopes has important engineering significance. | Rocky slope with weak interlayers, New combined anti-slide piles, Reinforcement mechanisms and effects, Earthquake
T09: Long term behaviour of underground structuresKimihiro HASHIBA, Katsunori FUKUIThe University of Tokyo, Tokyo, JapanEffects of water on the time dependent properties of rock1390 For the long-term stability assessment of underground structures, it is essential to understand the effects of water on the time dependent properties of rock, such as loading-rate dependence, creep, and relaxation. In this study, the relation between the loading-rate dependence of strength and the stress dependence of creep lifetime in dry and wet conditions was examined on the basis of the previous experimental results of a tuff. It was found that the results of strength and short-term creep tests in dry and wet conditions are consistently explained with the rate process theory, which indicates that creep lifetime can be estimated from the loading-rate dependence of strength in a dry or wet condition. Using these theoretical and experimental findings, the creep lifetime in the ongoing 25-year creep test was predicted. | rock, strength, loading-rate dependence, creep, water
T13: Numerical methods in rock engineeringGerold LENZiC consulenten ZT GesmbH, AustriaExcavation stability of deep tunnels in water-bearing fault zones1393 Groundwater is one major reason for tunnel collapses throughout history. Tectonic fault zones, characterized by heterogeneous rock mass composition and low strength, are particularly prone to such events. The article describes the groundwater conditions in heterogeneous ground at high overburden, revealing that high hydraulic gradients may develop close to the face in such situations. Numerical analyses with full hydraulic-mechanical coupling indicate a poorly confined region, subject to seepage forces, forming ahead of the face when approaching a fault zone. The governing hydraulic failure mechanisms for excavation stability can be distinguished into seepage-force driven mechanical failures (so called plug failure and cracking) and erosion processes. For the former, the article describes a novel solution to assess tunnel face stability subject to seepage forces, based on the method of slices applied to a hemispherical failure body. | flowing ground, groundwater, seepage, fault zone, deep tunnel, face stability
T07: Geological risks and natural hazardsHippolyte DJIZANNE (1), Marwan AL HEIB (2), Aurélien GOUZY (1), Christian FRANCK (1)1: Ineris, Parc Technologique ALATA, BP 2, Verneuil-en-Halatte, France; 2: Ineris, Campus ARTEM, Nancy, FranceDevelopment of post-mining multi-hazard assessment methodology1394 Mining, natural and technological hazards can occur in a former mining site. The multi-hazard analysis becomes critical. This paper aims to establish the methodological basis for assessing the interactions between the main hazards identified in abandoned mines. The interactions between 57 hazards are analysed based on: theoretical aspects, feedback analysis and expert opinions. Interaction matrices and loops are used, helping to study the interactions between hazards. | abandoned mine, multi-hazard, interaction, matrix, loop
T13: Numerical methods in rock engineeringRafael Arturo RUBIO RUIZ (1), Timo SAKSALA (1,2), Alexandre KANE (3), Mikko HOKKA (1)1: Faculty of Engineering and Natural Sciences, Tampere University, Finland; 2: Faculty of Built Environment, Tampere University, Finland; 3: Sintef Industry, NorwayA numerical analysis of weakening of a granitic rock by piezoelectric excitation of quartz1395 This work presents a numerical model to simulate intergranular damage in a granitic rock by oscillating piezoelectric excitation of quartz dispersed in the structure. The damage evolution at grain boundaries was assumed to be related to fatigue and it was modelled using cohesive elements and a damage evolution model formulated in terms of discipation of mechanical work. An explicit representation of the granular mesostructure was built, and it was subjected to high-voltage alternating-current exitation. The effect of the fatigue damage on the mechanical properties was quantified by simulated tension and compression tests. The numerical results show that the electrical treatment can potentially cause rock weakening due to fatigue, but the model needs to be calibrated with experimental data for a quantitative analysis. | Piezoelectric actuation, High voltage, High frequency, Alternating current, Rock fracture, Damage cyclic evolution
T06: Geological investigation and characterizationArthur D. DE ALWIS (1), Mehdi SERATI (1), Derek MARTIN (2), Arcady DYSKIN (3), Elena PASTERNAK (3), David J. WILLIAMS (1)1: The University of Queensland, Australia; 2: The University of Alberta, Canada; 3: The University of Western Australia, AustraliaAcoustic Emission Characteristics of Mode I Rock Fracturing1397 Understanding the propagation of Mode I fracture is crucial in rock mechanics since this fracture mode is the predominant cause of catastrophic failures in brittle rock-like solids. For investigating the mechanisms of rock fracturing, Acoustic Emission (AE) is a widely accepted tool. In this paper, various AE parameters, including the number of hits, source location, Rise Angle (RA), and Average Frequency (AF) are considered to evaluate the AE characteristics during Mode I loading-induced fracturing of basalt. Certain waveform features such as the dominant frequency and amplitude distribution are further investigated. Results suggest interesting findings in the changes in cumulative hits, source location, and RA at different stages of fracture. The observed trend in peak frequencies found in the study, in particular, points to promising future studies. | Mode I Rock Fracture, Acoustic Emission, Source Location, Rise Angle, Average Frequency, Dominant Frequency
T07: Geological risks and natural hazardsAbhijeet SINGH, Deepanshu SHIROLEIndian Institute of Technology, Delhi, IndiaExperimental simulation of mass flow characteristics for evaluation of the role of flow-bed roughness1399 One of the significant geohazards associated with rock slopes is the avalanche. The mechanisms associated with such events are commonly studied under controlled settings of a laboratory scale analog as typical field conditions are inherently complex and uncertain. Accordingly, in this study, experiments on a novel laboratory-scale avalanche simulating system were performed to examine the flow and deposit characteristics of dry granular silica sand with the help of high-speed camera. The model consists of a fully regulated rigid flow-bed (0.6 m), on which the tests were performed at 36o, 42o and 47o angles of inclination, with frictionless (mica) and rough (P120 sandpaper) surfaces. The results showed that: (i) runout and deposit length on a smooth bed were greater than those on a rough surface, (ii) the height and width of deposit were greater on rough surfaces, and (iii) deposit width was not significantly affected by changes in the inclination angle. | Avalanche, bed friction, dry granular flow, granular mass deposit characteristics
T15: Rock and rock mass propertiesAmin HEKMATNEJAD (1), Eduardo ROJAS (2), Alvaro PEÑA (3), Benoit CRESPIN (4)1: Pontificia Universidad Católica de Valparaiso, Chile; 2: CODELCO, Chile; 3: Pontificia Universidad Católica de Valparaiso, Chile; 4: University of Limoges, FranceSpatial modeling of rock strength heterogeneity and anisotropy using Universal Discontinuity index (UDi)1400 Rock strength anisotropy and heterogeneity are two key properties of various types of rocks. Discontinuities are the most significant factor on the anisotropic and heterogeneous behavior of rock mass strength. In this study, Universal Discontinuity index (UDi) applied to spatial modeling of the anisotropic and heterogeneous behavior of rock mass due to presence of discontinuities around a tunnel for the prediction of the geometry of over-excavation. UDi is based on the state of the art of the rock mass characterization systems and rock failure criteria. More precisely, UDi combines the quantitative and measurable parameters of the discontinuity network including volumetric discontinuity intensity (P32), the orientation of the discontinuities, vectorial based criteria of Warburton for kinematic rock block failure, and Mohr-Columb criteria for shear failure analysis. The results of this are validated through comparison with observed over-excavation at field data. | Rock strength anisotropy and heterogeneity, Universal Discontinuity index, rock block failure, shear failure, over-excavation
T06: Geological investigation and characterizationHolger JUD (1), Dieter TRONICH (1), Gerd SIEBENBORN (2)1: Smoltczyk & Partner, Germany; 2: Wasserstraßen- und Schifffahrtsamt Elbe-NordseeStructural and Geotechnical Investigations for the Remediation of Jetties and Seawalls on Heligoland1401 Heligoland is a German offshore island located about 50 km from the German coastline in the North Sea. Storm surges, especially in 1954, caused massive destruction and damage to the jetties and seawalls. Moreover, the "Big Bang" blast in 1947 as well as wartime bombardments lead to extensive rock fracturing. Due to these impacts the jetties and seawalls displayed serious structural deficiencies, such as differential settlements and potential instabilities. Against this background, a site investigation was carried out for the geotechnical design of the remedial measures. Special drilling rigs were used, equipped with an interchangeable drill head for both sonic and wireline drilling methods while incorporating an automatic drilling data acquisition system. This allowed high quality structural and rock cores and samples to be obtained in accordance with sampling and testing standards. | Investigation, Sonic drilling, automatic drilling data acquisition, geological modelling
T15: Rock and rock mass propertiesKiyotoshi SAKAGUCHI, Yuta SHIROSAWATohoku University, JapanSize effect and correlation with hardness of the microscopic fracture toughness of the minerals of granite1402 Microscopic fracture toughness (MFT) tests on the minerals composing the Inada granite (quartz, K-feldspar, plagioclase, biotite) were conducted to elucidate the fracture phenomenon of rock. MFT tests were conducted with three cantilevered specimens of micrometer size. The MFT of mineral was in the order of quartz, plagioclase, K-feldspar, and biotite from the largest value. Those MFT were lesser than the macroscopic fracture toughness of the Inada granite evaluated by the SCB test. In addition, the mineral grain boundary MFT was smaller than the mineral MFT. We found no significant scale dependence for the MFT itself. It was suggested that macroscopic fracture toughness of Inada granite may be controlled by quartz, which has a large composition ratio and large MFT. Furthermore, it was clarified that the MFT of each mineral has a positive correlation with the Vickers hardness, which are indicators of the hardness of the minerals. | Microscopic fracture toughness, Mineral grain, Mineral grain boundary, Size effect, Hardness
T15: Rock and rock mass propertiesBunyuu HASEGAWA (2), Sota HIGASHI (1), Atsushi SAINOKI (1)1: Kumamoto University, Japan; 2: Tokyo University, JapanElucidation of microscopic stress state within surface asperities of a rock joint1404 Field observations suggest that the occurrence of fault-slip related seismicity in deep underground be affected by the non-linear and/or time-dependent behaviour of discontinuity surface asperities. The present study aims at investigating the strain and stress distribution of discontinuity surface asperities on a micro scale by conducting a uniaxial test in a micro-focused X-ray CT, analyzing the CT images with the digital image correlation method, and reproducing the experiment with numerical simulation in the framework of the discrete element method. The experimental result obviously shows strain concentration within asperities on the discontinuity, which is approximately 10 times as large as that in the matrix. Surprisingly, the numerical simulation shows an asperity to matrix strain ratio similar to the experiment, although the absolute value is different. It was then concluded that the difference is attributed to time-dependent and/or brittle failure behaviour of the highly stressed asperity. | Discontinuity asperity, DIC, micro-focused X-ray CT, DEM simulation
T08: Hydropower projects and damsRupert STEIGER (1), Peter WETZLINGER (2)1: TIWAG, Austria; 2: Swietelsky, AustriaHEPP cavern Kühtai, excavation design and construction experience1405 The Pumped Storage Scheme Kühtai 2 located between the existing reservoir Finstertal and the currently under construction reservoir Kühtai is part of the expansion of the existing hydro power plant group Sellrain-Silz. The new power station is housed in a cavern at an altitude of 2000 meters above sea level near the village of Kühtai in Sellraintal. The cavern is located within a gneiss formation (biotite-plagioclase gneiss), which is layered in bands and tectonically faulted. As the design progressed, a number of variants were investigated, including the simulation of different geological conditions, the variation of distance between the individual caverns (double cavern solution with machine cavern and separate transformer cavern), the arrangement of tunnels surrounding the caverns and the complex construction process, until a solution was developed. The paper provides an overview to the excavation design process as well as to the geotechnical design analyses, which were adopted, and the experience gained during the excavation of the caverns. | Cavern excavation design, construction experience
T13: Numerical methods in rock engineeringTatsuki TOKUDA (1), Ryota HASHIMOTO (2)1: Hiroshima University, Japan; 2: Kyoto University, JapanDevelopment of an efficient parallelization scheme for fully implicit discontinuous deformation analysis (dda)1406 In this study, we propose a parallelization scheme for the fully implicit Discontinuous Deformation Analysis (FI-DDA) to establish an accurate and efficient numerical method for the dynamic stability analysis of rock slopes. Specifically, a parallel iterative linear equation solver was newly introduced to the FI-DDA, and then, efficient contact detection and contact stiffness matrix assembly algorithms suitable for parallel processing were proposed and introduced to the FI-DDA. The analysis code was parallelized with OpenMP and the performance of the developed method was verified by simulating a centrifugal model shaking table experiment of discontinuous rock slope. | DDA, OpenMP, rock slope, parallelization
T06: Geological investigation and characterizationNana KAMIYA, Weiren LINKyoto University, JapanOne-dimensional consolidation properties of sedimentary soft rocks from the Boso Peninsula, central Japan using a constant strain-rate loading system1407 Consolidation property is an indicator of load bearing capacity of foundation and also reflects the process of geological evolution. In general, consolidation test has been performed for soil materials in geotechnical area, however we tried to conduct consolidation test using Mio–Pleistocene sedimentary rocks taken from a forearc basin located at a subduction zone. Consolidation yield stress almost increased as porosity decreases, however consolidation yield stress has variation in same porosity and it was increased with depth of sampling point, that indicates the consolidation line of this setting and the consolidation yield stress would record the maximum burial depth of the basin. SEM images show the consolidation fabric which has layer structure and high-resolution X-ray CT images show a deformation during the consolidation test. | Sedimentary soft rock, consolidation test, consolidation yield stress, X-ray CT image
T04: Deep mining and tunnellingTatsuya YOKOYAMA (1), Akira MITO (2)1: Fukada Geological Institute, Tokyo, Japan; 2: Shimizu corporation, Tokyo, JapanEvaluation of rock stresses measured in a long water tunnel at deep depth1408 Three different methods were used to measure stress in a deep tunnel under excavation, and the obtained values were compared. At two locations at a depth around 200m, the stress relief method (CCBO) and the hydraulic fracturing method (HF) were used. The stress states measured at these points have large horizontal stress components, and the maximum principal stresses were greater than the overburden stress. The stress states measured by CCBO and HF agreed well with each other. At a depth of location of 1,130m, CCBO and the Borehole Wall Strain method (BWS) were used. Assuming that the tunnel itself is a large borehole, stress measurements by BWS were obtained by gluing strain gauges directly to the tunnel wall and releasing stress only in that part. This BWS is a very unique and challenging method. Interestingly, the stress states measured by two different methods were in good agreement with each other. | Rock stress. Stress relief method (CCBO). Hydraulic fracturing method (HF). Borehole wall strain method (BWS)
T10: MonitoringRoberto SARRO (1), Juan LÓPEZ-VINIELLES (1), Adrián RIQUELME (2), Mónica MARTÍNEZ-CORBELLA (1), Juan Carlos GARCÍA-DAVALILLO (1), Augusto RODRÍGUEZ (1), José Antonio FERNANDEZ-MERODO (1), Ángela SUÁREZ-RODRÍGUEZ (1), Mario HERNÁNDEZ (1), Rosa María MATEOS (1), Mercedes FERRER (1), Joaquín MULAS (1)1: Geological Survey of Spain (IGME-CSIC); 2: University of AlicanteAnalysis of the evolution of a reclaimed coal mining area using historical aerial photographs1409 Mining activities have a significant impact on the environment, and it is crucial for mining companies to restore the land after extraction and preserve the original landscape. Remote-sensing techniques, such as Structure-from-Motion and 3D laser scanners, have become widely used in mining for ground monitoring due to their accessibility and safety advantages. In this study, historical aerial optical imagery of a coal-mining site in León, Spain, was processed using SfM photogrammetry to analyze landscape changes from the beginning of the open-pit operation to the completion of land reclamation. Two point clouds generated from open-access optical imagery were compared with a LiDAR point cloud from 2010. To ensure accurate georeferencing, ground control points were extracted from an additional LiDAR point cloud acquired in 2010. By comparing these reconstructions and conducting a comprehensive analysis of the site's evolution, the researchers identified a landfill and assessed the effectiveness of the mine reclamation works. | Landslide, Coal mining, SfM, Land restoration, Aerial photographs
T13: Numerical methods in rock engineeringBikash CHAUDHARY (1), Krishna Kanta PANTHI (1), Nghia Quoc TRINH (2)1: NTNU, Norway; 2: SINTEF, NorwayAssessment on the in-situ rock stress condition along an unlined pressure tunnel/shaft of a Norwegian Hydropower Project using numerical modeling1411 Confinement is a pre-requisite in the “Norwegian state-of-art design principles” for unlined pressure tunnels/shafts where the minimum principal stress must exceed internal water pressure. Reliable estimation of in-situ stress state is crucial in implementing unlined pressure tunnels/shafts so that hydraulic jacking/fracturing in the rock mass is avoided. The Norwegian thumb rule may not offer a complete solution in all unlined pressure tunnels/shafts since these are based on the 2D geometry of terrain and thus do not fully represent the in-situ stress environment in 3D. This article evaluates the minimum principal stress state of the unlined headrace system of Bjørnstokk powerplant using 3D numerical modeling. The 3D model is developed with the integration of geological, topographic, and geotectonic features. The model is calibrated using measured in-situ stress data of fixed locations along the waterway system. Discussions are made on how in-situ rock stress differs upon changes in topography and geological setting. | Unlined Pressure Tunnels, Minimum Principal Stress, In-situ Stress, Shear Planes, Numerical Modeling
T15: Rock and rock mass propertiesLeona VAVRO (1), Martin VAVRO (1), Minami KATAOKA (2)1: The Czech Academy of Sciences, Institute of Geonics; 2: The University of Tokyo, Department of Systems InnovationDetermination of an empirical relations between mode I fracture toughness using CB and SCB specimens and Brazilian tensile strength of rocks1412 Fracture toughness (FT) expresses material resistance to crack propagation leading to its final macroscopic failure. Approximatelly 20 different laboratory methods are currently used for a mode I and mixed mode I/II FT rock testing. However, it is a well-known fact that, for the same rock, the mode I FT value varies when different specimen types are utilized. Moreover, the preparation of specimens for FT testing may be associated with difficulties in obtaining required notch dimensions. From this point of view, Brazilian tensile strength (BTS) represents an easily and quickly detectable parameter that can be applied for prediction of the mode I FT. In this contribution, the results of investigations of mutual empirical relationships between FT determined using CB and SCB tests, as well as among FT values obtained via these testing methods and BTS are presented. A total of 14 different rock types, mostly sandstones, were used for this research. | rock, mode I fracture toughness, CB specimen, SCB specimen, Brazilian tensile strength
T13: Numerical methods in rock engineeringSaurav KARN (1), Ian PORTER (2), Shivakumar KAREKAL (2)1: BHP, Australia; 2: University of Wollongong, AustraliaNumerical investigation of the behaviour of underground strata reinforced with polymer liner, steel mesh and bolts subjected to buckling failure1413 In this work, numerical models are developed to compare the support characteristics of a glass reinforced polymeric liner and steel mesh in supporting coal mine roof strata subject to buckling failure. The numerical models consisted of four plaster slabs bolted together and loaded under compression to mimic roof strata having rock bolts in a highly stressed mine roadway. The liner supported model showed greater stiffness and peak strength than the steel mesh model and were in good agreement with the experimental results. The bolts only and the steel mesh supported models were found to fail in tension with cracks originating near the centre of the outer slab and propagating inwards. However, as a result of strong bonding of the liner, no tensile cracks formed in the outer plaster slab and the liner supported model failed under shear alongside the interface of the liner. | Thin spray-on liners, Fibre-reinforced polymers, Steel mesh, Numerical modelling, Buckling strata
T08: Hydropower projects and damsTek Bahadur KATUWAL (1,2), Krishna Kanta PANTHI (1), Chhatra Bahadur BASNET (2)1: Norwegian University of Science and Technology, Trondheim, Norway; 2: Tribhuvan University, IOE, Pashchimanchal Campus, Pokhara, NepalChallenges associated with the construction of vertical and inclined shafts in the Himalayan Region1414 In the Nepal Himalayas, hydropower projects having an installed capacity of over 10 MW usually consist of underground waterways. Most of these underground waterways consist of vertical or inclined pressure shafts, which are part of the headrace system of a hydropower project. Excavation of these shafts requires special techniques, and the performance is dependent on the quality of rock mass. Therefore, the selection of an efficient construction method for shaft excavation is most challenging work. This manuscript evaluates the challenges associated with the construction of shafts for three hydropower projects in the Nepal Himalayas. The achieved construction progress of each method is compared with actual geological conditions. It is concluded that the major challenges associated with the excavation of pressure shafts through the Himalayan rock mass conditions are frequent overbreak, water inflow, debris flow, difficulties in surveying and control of shaft alignment, ventilation, poor visibility, and pilot hole deviation. | Vertical/inclined Shafts, Construction methods, Himalayan rock mass, Overbreak
T07: Geological risks and natural hazardsSusumu SHIBUTANI (1), Weiren LIN (2), Koichiro SADO (1)1: Chi-ken Sogo Consultants Co., Ltd., Japan; 2: Graduate School of Engineering, Kyoto University, JapanFracture characteristics obtained from core observations and image logs in a borehole drilled through an active fault zone1415 Fracture characteristics in and around active fault zones are required for understanding hydrogeological characteristics along fault zones. To examine the fracture characteristics, we used core samples and geophysical log data collected from the Futagawa fault drilling project. Fracture density and angle of dip were quantitatively measured using core samples. As a result, the closed fractures with semiconsolidated brown clays were revealed dominant along the Fault 461 damage zone ruptured during 2016 Kumamoto earthquake mainshock, and the fracture density were higher in volcanic rocks than that in sedimentary rocks, and fractures were mainly oblique fractures with respect to the strike of the active fault. Kumamoto earthquake occurred at Fault 461 damage zone characterized by closed fractures, it suggests that the fault may have ruptured at the low permeability zone. | fracture density, active fault, core, image log, 2016 Kumamoto earthquake
T04: Deep mining and tunnellingSevda DEHKHODA (1), David BECK (1), Vladislav LEVKOVITCH (2)1: Beck Engineering, Australia; 2: Beck Engineering, GermanyNumerically simulated Rate of Energy Release and its correlation with measured seismic potency1416 As mines are getting deeper, mining induced seismicity becomes a major hazard threatening the health, safety, and security of operations. In today’s mines, seismicity is well measured and documented. However, the ability to foresee events lags behind. This paper will discuss the correlation between numerically simulated Rate of Energy Release (RER) and measured seismic potency in the real rock mass. RER is defined as the rate of elastic strain energy emitted into the surrounding rock as a result of abrupt fracture or deformation. RER has proven to be a good candidate for probabilistic forecasting of seismic potential (the capacity to develop seismogenic activity) in the rock mass. In the following sections, we will describe a computational framework for simulating RER and subsequent analyses for evaluating the likelihood of mining induced seismic events. We will present example results from mines where model predictions matched measured seismicity. | Mining induced seismicity, rate of energy release, RER, hazard management, seismicity forecast
T01: Challenging rock engineering projectsManuel BODE (1), Magdalena SALLINGER (1), Paolo ZANANDREA (2), Thomas MARCHER (1)1: SKAVA Consulting ZT GmbH, Austria; 2: Ingenieurgemeinschaft GMK, ItalyHard Rock Caverns with low overburden in urban environment – a case study1417 The design and the construction of underground caverns with low overburden in an urban environment is a sophisticated task. The project of an urban parking garage, which is built within a large span cavern construction is presented. Due to its low overburden, combined with the dominating behaviour of the jointed rock mass, there was a need of complex modelling techniques and considerations in design. The contribution gives an overview over the project, including the morphology, the ground investigation and classification and special risk scenarios. It also provides an insight in the design of the excavation process, the support measures and the accompanying monitoring process. | Cavern, urban environment, low overburden, analysis and design, jointed rock
T07: Geological risks and natural hazardsKosuke KAWATA (1), Minaho FUKUSHIMA (1), Akira MATSUOKA (1), Atsushi KUSAKA (2), Nobuharu ISAGO (1)1: Tokyo Metropolitan University, Japan; 2: Public Works Research Institute, JapanCharacteristics of reinforcement for earthquake resistance in mountain tunnel1419 In Japan, some mountain tunnels are damaged by earthquakes and relative large-scale deformations such as the collapse of permanent lining and the deformation of supports have occurred. Although the earthquake resistant countermeasures for tunnels has been examined recently, some countermeasures for existing tunnels are performed on the result of tunnel inspection rather than the need against earthquake resistance. To clarify the effects and the mechanical behavior of countermeasures, the model experiment was conducted assuming the structure of actual road tunnels. The collapse mechanism was compared among the cases when various kinds of reinforcement to tunnel were performed, such as rockbolts, fiber sheet and rebar. Results showed that the improvement of load-bearing capacity of the tunnel was limited, however the prevention of falling concrete blocks from structure could be expected. | mountain tunnel, earthquake, seismic measures, rehabilitation measures, experiment
T13: Numerical methods in rock engineeringSajad NAMDARI (1), Alireza BAGHBANAN (1), Hamid HASHEMOLHOSSEINI (2)1: Department of mining engineering, Isfahan University of Technology (IUT), Isfahan, Iran; 2: Department of civil engineering, Isfahan University of Technology (IUT), Isfahan, IranA fast and novel hybrid technique for simulation of fluid flow in large-scale fractured rock masses using streamline method and modified Bresenham line algorithm1422 The most popular numerical method for simulating fluid flow in fractured rock masses is distinct element method (DEM), which suffers from being numerically expensive. Streamline simulation (SL) is a fast method for homogeneous porous media. In this research, a MATLAB code (IUT-SL) is developed to study the flow behavior in a fractured porous media using SL. Using a Finite Volume discretization (FVM) and Discrete Fracture Network (DFN) to simulate rock matrix and fracture network, Bresenham line algorithm is used to embed the DFN into FVM cells. Pressure equations are solved with a two-point flux approximation (TPFA) scheme and Streamlines were traced in the medium via Pollock’s semi-analytical method along with Time of Flight (ToF). The results show that FVM-DFN-SL hybrid technique can be used as an efficient alternative for DEM approaches, which not only can preserve the accuracy of DEM methods, but also has orders of magnitude faster runtime. | streamline, Finite Volume, Discrete Fracture Network, Bresenham line algorithm
T07: Geological risks and natural hazardsBenjamin COUGHLAN (1), Christian SAMPALEANU (2), Glyn WILLIAMS-JONES (1), Doug STEAD (1)1: Simon Fraser University, Canada; 2: Klohn Crippen BergerRockfall instability on high granitic domes: Stawamus Chief, B.C., Canada1423 The rock slope stability of high granitic-granodiorite domes has become of increasing concern over recent decades. As tourism increases in popularity the risk posed by rockfall from these domes has also increased. Using the 417 m high Stawamus Chief, in Squamish, BC, Canada as a case study, we describe the use of multi-sensor remote sensing in understanding the failure mechanisms and the factors controlling instability. The Grand Wall and the North Wall of Stawamus Chief experienced significant rockfalls in 2021. Remote sensing using LiDAR and thermal imaging has added to our understanding of rockfall at Stawamus Chief. The application of these methods is discussed through detailed characterization of the rock slopes. Evidence shows that potential causal failure processes include root jacking, freeze-thaw effects, heavy precipitation, and expansion of joints due to extreme heat. | Geohazards, Remote Sensing, Slope Stability, Rock Mechanics, Rockfall
T15: Rock and rock mass propertiesLiang ZHANG (1,2), Xiaopeng LI (1), Qingxin QI (1), Haitao LI (1)1: Deep Mining and Rockburst Research Institute, CCTEG Chinese Institute of Coal Science, Beijing, China; 2: State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, JiaoZuo, Henan, ChinaCracking evolution for deep hard coal using X-ray in-situ micro-CT technology and fractal theory1424 Rockburst poses severe threats to the deep mining of coal mines in China; however, the fracture mechanism of deep hard coal is still unknown. Hence, this paper focuses on the cracking evolution laws for deep hard coal with high-bursting liability utilizing X-ray in-situ micro-CT technology and fractal theory. The in-situ micro-CT scanning system and bursting liability indexes for deep hard coal are first introduced in this work. Then, the uniaxial compressive experiments for the coal samples using in-situ CT scanning are conducted. Furthermore, the crack initiation, propagation, and coalescence of coal are revealed based on the in-situ micro-CT scanning experiment results. The 3D digital core of coal is obtained; four typical parameters, including fracture volume fraction and fractal dimension in 2D and 3D, are used to characterize the fracture network evolution for deep hard coal during the progressive failure process. The findings are valuable in rockburst, damage, and fracture mechanics. | Deep mining, rockburst, hard coal, cracking evolution, in-situ micro-CT, fractal theory
T13: Numerical methods in rock engineeringHongyuan LIU (1), Daisuke FUKUDA (2), Haoyu HAN (3), Di WU (4), Qianbing ZHANG (5)1: School of Engineering, University of Tasmania, Hobart, Australia; 2: Faculty of Engineering, Hokkaido University, Sapporo, Japan; 3: School of Architecture and Planning, Yunnan University, Kunming, China; 4: Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, China; 5: Department of Civil Engineering, Monash University, Melbourne, AustraliaDevelopment and application of a grain-based hybrid finite-discrete element method for investigating fracture processes of heterogeneous rocks under static and dynamic loads1425 A both two- and three-dimensional grain-based hybrid finite-discrete element method (HFDEM-GB2D/3D) is developed and parallelized on the basis of the general-purpose graphic-processing-units. It is then calibrated by modelling the failure process of heterogeneous rocks in uniaxial compression tests. After that, it is applied to investigate the dynamic fracture process of heterogeneous rocks in triaxial Hopkinson bar tests. It is concluded that HFDEM-GB2D/3D can consider the actual microstructures of heterogeneous rocks to investigate the intra-, trans- and inter- granular crack propagations besides modelling the failure process of heterogeneous rocks. | Grain-based modelling, FDEM, intergranular failure, trans-granular failure, rock fracture, heterogeneity
T06: Geological investigation and characterizationEdward Alan BUTTONARUP Pft. Ltd., AustraliaAssessing Intact Rock Properties for the Salang Highway Tunnel Upgrade Route Selection Study1426 The current 2700m long Salang Tunnel at the time of completion was the highest road tunnel at 3400 m providing all-weather connectivity from northern Afghanistan to the southern regions and the capital Kabul. The Salang Corridor is a crucial link within the Central Asian Regional Economic Cooperation Program’s transportation network. The intact rock test results presented within this contribution are associated with work to identify and optimizing the central tunnel alignment to reduce the maximum elevation and optimize the road alignment. Eight boreholes were drilled between 150m and 220m depth to investigate the ground conditions and rock properties for three previously identified tunnel alignments, due to very poor ground conditions a 9th borehole was terminated at 42m depth. The results demonstrate that with appropriate sample selection and testing methods and procedures reliable and consistent data can be acquired to characterize and assess rock properties and associated tunnel hazards. | Rock testing, Brittle failure, Granite, Alpine Tunnelling
T05: Digitalization & AutomatisationWolfgang DOLSAK (1), Mislav MIKULEC (2)1: DSI Underground Austria GmbH, Austria; 2: RHI Magnesita GmbH, AustriaDevelopment and implementation of a sensor-supported rock bolt system for underground monitoring1427 Alongside with digitalization in underground mining and tunnel construction, user-friendly acquisition and processing of data is of paramount importance, considering the particularities of the working environment. Various conventional data measurement systems are currently in use for different applications; however, their scope is somehow isolated and not applied for a large-scale basis monitoring of default ground support systems such as rock bolts. For underground applications, system sourcing, and installation of special monitoring bolts is cost intensive and impracticable for a large-scale application. A low-cost intelligent rock bolt assembly concept was developed during the EU-funded illuMINEation project, part of the horizon 2020 research and innovation program. This low-cost intelligent rock bolt assembly allows an easy application with already installed rock bolts, or in combination with rock bolts featuring an integrated tendon sensor. The principal idea is to provide real-time recordings and visualization of geotechnical and environmental measurands on a large-scale collective basis. | ground support, rock bolt, monitoring, tendon sensor, illuMINEation
T02: Comparison of international tunnelling contractsDavide MERLINI (1), Daniele STOCKER (1), Matteo FALANESCA (1), Matthias NEUENSCHWANDER (2)1: Pini Group SA, Switzerland; 2: Neuenschwander Consulting Engineers, SwitzerlandCase Histories of contractual management of geological risks1428 The geo-uncertainty of underground projects most often leads to differences between foreseen and encountered geo-conditions. Dealing with this uncertainty is a major challenge as it often raises claims and complex contractual problems mostly related to the construction programme. Over the last years, contract management tools have been developed in order to manage this risk. One of the key aspects for the successful delivery is the elaboration of a mechanism to adjust the time for completion. The clear allocation of duties and risks between the Employer and the Contractor, together with its proper integration in the contractual frame-work, play a crucial role. This paper presents cases of implementation of such a contractual mechanism in several Countries, standard forms and excavation methods together with the comparison with the FIDIC standard. | Risk management, Forms of contract, Schedule of Baselines, FIDIC Standard
T15: Rock and rock mass propertiesNazlı TUNAR ÖZCAN (1), Elif AVŞAR (2)1: Hacettepe University; 2: Konya Technical UniversityA Study on Dynamic Shear Properties of Bimrock1429 Dynamic shear strength of rocks is of critical importance for rock mechanics and rock engineering applications. In this study, dynamic direct shear tests were carried out to investigate the dynamic shear strength of welded weak bimrocks and to determine the effect of volumetric block proportion (VBP) on dynamic shear behavior. For this purpose, artificial model bimrock specimens with different VBP were constituted, due to challenges in extracting undisturbed natural specimens. According to the results, most of the model specimens show strain hardening behavior after the dynamic shear failure occurs. The dynamic shear strength of specimens increases with the increase in the VBP values. In addition, the VBP of the shear failure surfaces at the end of the tests are obtained through digital image processing analyses. It is concluded that the VBP values of failure surfaces have an effect on the shear strength parameters as well as the overall VBP. | Bimrock, Dynamic Shear Strength, Dynamic Shear Test, Volumetric Block Proportion
T04: Deep mining and tunnellingDavide MERLINI (1), Matteo FALANESCA (1), Gianluca BELLA (1), Antonio SPAZIANI (2), Antonio VOZA (2)1: Pini Group SA, Switzerland; 2: BBT-SE, Bolzano, ItalyNumerical modelling and tunneling experience of the Emergency Stop in Trens, Lots Mules 2-3 (Italy) - Brenner Base Tunnel1430 The present paper focuses on the design and the construction experience related to Emergency Stop in Trens as a part of the Brenner Base Tunnel (BBT). This underground work consists in a 470 m long central tunnel excavated by conventional tunnelling connected through cross-passages every 90 m to the main tunnels excavated by TBMs-shield. The main design issues and construction challenges are represented by the complex interaction between underground structures located at two different elevations in combination with the high overburden about 1100 m and medium-low strength rock mass composed mainly of schists. The design involved 2D and 3D numerical analyses and also included swelling and creep. A comparison between the forecast geology and the cross-check will be analyzed also considering the data from the in-depth monitoring system. The comparison between Design and As-Built in terms of installed rock-supports, timing and costs will be examined in detail. | TBM and conventional tunneling, deep and long tunnel, BBT, numerical analysis
T13: Numerical methods in rock engineeringDavide MERLINI (1), Matteo FALANESCA (1), Filippo GIANELLI (1), Gianluca BELLA (1), Roberto SCHÜRCH (1), Anastasia LOPEZ- HERNANDEZ (2)1: Pini Group SA, Switzerland; 2: CERN, SwitzerlandCERN (HL-LHC): challenges and tunneling experience for the design of new underground structures at Point 51431 This paper deals with the main challenges and design issues raised for the construction of new underground structures at Point 5 close to the largest underground particle accelerator in the world (Large Hadron Collider). The High-Luminosity LHC is a new project aimed to upgrade the accelerator at Point 1 (ATLAS, Switzerland) and Point 5 (CMS, France), by increasing the number of atomic collisions. The new project requires an additional shaft, a cavern, galleries, vertical linkage cores and technical buildings at the surface. To predict the complex response of the heterogeneous rock mass and evaluate the impact of the excavation phases on the nearby existing structures, 2D and 3D finite element and finite difference models were realized, allowing to design both the rock-supports and the concrete inner lining for all the structures. The observational method was applied during the construction phase to verify the hypothesis used in the numerical calculations. | Numerical analysis, Rocks mechanics, Underground works, Observational method
T05: Digitalization & AutomatisationAlexander ZÖHRER (1), Vincent WINTER (1), Anika TERBUCH (2), Paul O'LEARY (2), Negin KHALILI-MOTLAGH-KASMAEI (2)1: Keller Grundbau GesmbH, Austria; 2: University of Leoben, AustriaApplication of hybrid machine learning based quality control in daily site management1433 This paper presents a system that combines KPI with autoencoders to implement a hybrid machine learning system. The goal here is to investigate workflows which permit the site manager to use the hybrid machine learning systems as a decision support tool. The workflows are explained by means of case studies, demonstrating the application of the hybrid system to detect both element as well as site related quality issues. In addition to that, the detection of anomalies regarding execution efficiency assist the project manager to optimize the sequence of work on site. | ground improvement, quality control, machine learning, key performance indicators
T01: Challenging rock engineering projectsAnton KALTENBÖCK, Martin PURUCKER, Bernhard STACHERLGeoconsult ZT GmbH, Puch bei Hallein, AustriaThe Blue Line Jerusalem LRT Underground Section – Public Transport in a challenging Project environment1434 The 2 km long Blue Line Underground Section is part of a 20 km long LRT line currently being developed as part of the Jerusalem Mass Transit Master Plan. The Underground Section of the Blue Line is characterized by narrow streets, limited right of way, steep gradients, small alignment radii turns and crossings with other LRT lines. The geological conditions feature different formations of limestone and dolomite. Karst is a known frequent phenomenon in the Jerusalem region which must be considered in the design and construction process. This publication describes the key criteria to be addressed in the design, such as the overall design approach for the large span station tunnels, geological risks especially in relation to karst, the impact on existing buildings and the insertion of the underground stations in a highly sensitive urban environment with very limited available space. | Tunneling, Underground, Karst, NATM, Monitoring
T17: Rock slope engineeringMariella ILLEDITSCH (1,2), Alexander PREH (1,2), Johann Thomas SAUSGRUBER (3)1: pi Geotechnik ZT GmbH, Austria; 2: Vienna University of Technology, Austria; 3: Federal Ministry Republic of Austria - Agriculture, Forestry, Regions and Water Management, AustriaThe Correct Way to use the Hoek-Brown Strength Criterion for Slope Stability Analysis on the Example of Vals (Tyrol/Austria)1435 The Hoek-Brown (HB) strength criterion is increasingly used to investigate the stability of slopes. However, it is still partly unclear how this should be implemented for slopes in a correct way. There are two ways to use the HB strength criterion. On the one hand, the HB parameters can be converted into equivalent Mohr-Coulomb (MC) parameters by estimating a suitable range of minor principal stresses. The result is a linear failure envelope. On the other hand, the nonlinear HB failure envelope can be applied directly by calculating apparent MC parameters for each point of the HB failure envelope. The result is a nonlinear failure envelope. Equivalent MC model parameters are usually used in numerical model calculations. However, this approach has some disadvantages. On the example of Vals, where a rock fall of about 117,000 m³ occurred in December 2017, a new method for using apparent MC parameters is presented. | Rock Slope, Hoek-Brown Criterion, Stability Analysis, Strength Reduction Method, Continuum Mechanics, Equivalent Mohr-Coulomb Parameters
T04: Deep mining and tunnellingLinard CANTIENI (1), Alexandros N. NORDAS (2), Dennis MOROSOLI (2), Georg ANAGNOSTOU (2)1: National Cooperative for the Disposal of Radioactive Waste (Nagra), Wettingen, Switzerland; 2: ETH Zurich, Zurich, SwitzerlandOn the short-term response of Opalinus Clay to tunnelling1436 Opalinus Clay is the host rock for the Swiss deep radioactive waste repository. Effective stress analyses have been performed for a first assessment of hazards related to the short-term ground response to the excavation of the repository drifts and caverns. The analyses were performed assuming that the rock either remains saturated or completely desaturates under the negative pore pressures developing short-term around the tunnels due to cavity unloading. The results show that the risk of shield jamming during construction of the repository drifts can be mitigated by providing an over-cut in the range of just a few centimetres. Yielding support is planned for the construction of repository caverns in order to accommodate deformations and reduce rock pressure. An over-excavation of one to two decimetres, in combination with adequate structural detailing, must be planned to accommodate the short-term convergences. | radioactive waste repositories, Opalinus Clay, brittle softening, squeezing ground, short-term, negative pore pressure cut-off
T01: Challenging rock engineering projectsGerhard GOBIET, Gernot NIPITSCH, Oliver Kai WAGNERÖBB Infrastruktur AG, AustriaSemmering Base Tunnel (SBT) - current state of the project1440 The Semmering Base Tunnel (SBT) is about 27.3 km long and driven from the portal at Gloggnitz and three intermediate construction accesses in Göstritz, Fröschnitzgraben and Grautschenhof. The main components of the tunnel system are two single-track tunnels, cross passages at a maximum distance of 500 m and an emergency station in the middle tunnel section, with two ventilation shafts with a depth of approx. 400 m in case of an incident. For reasons concerning organization, timetable and topography, the tunnel is divided into four construction contracts. Construction work of the tunnels started in 2014. By autumn 2023 98% of the tunnel excavation is completed. In the landfill site in Longsgraben, where most of the excavated material is deposited, recultivation started. The presentation highlights the current state of the project, present achievements, and an outlook to further works. | Semmering Base Tunnel, general scope, state of project, tunnelling
T06: Geological investigation and characterizationIrmina PÖSCHL (1), Walter FREI (2)1: iC consulenten ZT GmbH, Austria; 2: GeoExpert AG, SwitzerlandThe use of dynamic moduli logging in large-scale geotechnical modelling1441 The dynamic elasticity rock mass modulus was used as reference parameter for developing large-scale geotechnical models. Modulus values were derived from p- & s-wave seismic refraction surveys. Hybrid seismic surveying, an increasingly applied combination of refraction and reflection seismic testing, proved being a particularly helpful tool for delivering the data necessary for a comprehensive interpretation of modulus distribution. Seismic surveying provides large amounts of spatially continuous data coverage at relatively small cost and time effort. Due to the non-intrusive nature of probing, the recorded data type reflects in-situ conditions, not corrupted by invasive procedures. Adequately processed, the data can be directly transferred into digital models for visualization, evaluation and interpretation. The experiences made from survey programs with different investigation methods and targets opened new perspectives for rock mass characterization, but also disclosed limitations to be considered for a successful application. | Elasticity modulus, hybrid seismic surveying, seismic refraction tomography, reflection seismic surveying, 3D modelling
T06: Geological investigation and characterizationJose Antonio VALIDO GARCÍA (1), Luis Enrique HERNÁNDEZ GUTIÉRREZ (2,3), José Miguel CÁCERES ALVARADO (1), Carlos Javier PÉREZ GONZÁLEZ (4)1: Instituto Universitario de Materiales y Nanotecnología. Departamento de Ingeniería Industrial, Universidad de La Laguna, La Laguna, Spain; 2: Consejería de Obras Públicas, Transportes y Vivienda. Gobierno de Canarias, Santa Cruz de Tenerife, Spain; 3: Instituto Volcanológico de Canarias” (INVOLCAN), Tenerife, Canary Islands, Spain; 4: Departamento de Matemáticas, Estadística e Investigación Operativa, Universidad de La Laguna, La Laguna, SpainSimple and multiple regression study of physical-mechanical properties of ignimbrites1444 The objective of this study is to analyse the relationship between uniaxial compressive strength (UCS) with physical properties, such as apparent density (AD) and ultrasound velocity (PWV), and with other mechanical properties, such as point load test (PLT) and indirect tensile strength (BTS). This analysis was carried out on a group of ignimbrites, consisting of a total of 45 samples, from the Canary Islands and consisted of applying simple regression and multiple regression methods. Applying the simple regression method, it was determined that the ultrasound velocity (PWV) is the property that explains the variability of the compressive strength (UCS) to the greatest extent. Using the multiple regression method, a model capable of increasing the proportion of variability of the (UCS) is obtained, using the apparent density (AD), the ultrasound velocity (PWV) and the point load test (PLT) as independent variables. | Canary Island, ignimbrite, boreholes, geomechanical properties, regression
T10: MonitoringSepidehalsadat HENDI, Erik EBERHARDT, Mostafa GORJIANUniversity of British Columbia, CanadaDevelopment of a non-destructive stress measurement method using distributed fiber optic sensing and geophysical techniques1445 In-situ stress is a critical boundary condition that dictates many important rock engineering design decisions such as the orientation, dimensioning and support design of underground excavations for mining and civil infrastructure to ensure stability and safety, as well as the optimal orientation of horizontal boreholes for energy development projects (geothermal, unconventional gas). However, it is also one of the most difficult parameters to measure reliably, resulting in significant uncertainty and risk to these projects. This has seen the development of numerous stress measurement techniques, each with its limitations and reliability issues. Presented here are the first steps in the conceptualization and workflow for a non-destructive stress measurement technique using distributed fiber optic sensing and geophysical techniques that overcomes several key challenges and limitations, while adding value through increased measurement resolution and reliability. Numerical workflow results are presented that compare favorably with values based on experimental results. | In-situ stress, distributed sensing, fiber optics, stress measurement, borehole geophysics
T15: Rock and rock mass propertiesChangshuo WANG, Shigui DU, Weiming LIU, Rui YONG, Zhanyou LUOInstitute of Rock Mechanics, Ningbo University, Ningbo, Zhejiang, ChinaInvestigation on the influence of non-stationary trend on the shear strength of rock joints1449 The non-stationary trend of rock joints significantly affects the shear strength of rock joints. Taking the least square fitting plane of a rock joint as a reference plane, two trend direction parameters α and β of the rock joint are proposed to characterize the non-stationary trend of rock joints quantitatively. α is the inclination angle of the rock joint along the shearing direction, and β is the deflection angle of the rock joint perpendicular to the shearing direction. Based on the trend direction parameters, the external normal and tangential stresses are decomposed into the normal and tangential stresses on the reference plane. Consequently, a rock joint shear strength model is established. Next, samples of different sizes are obtained from a large rock joint. Based on the established shear strength model, the shear strengths of the rock joint samples in different sizes under the influence of non-stationary trends are statistically analyzed. | Rock mechanics, rock joint, roughness, shear strength, non-stationary trend
T09: Long term behaviour of underground structuresWen-Jie SHIU (1), Fu-Yuan HSIAO (1), Cheng-Hsien TSAI (1), Shih-Hui WANG (2)1: Sinotech, Taiwan; 2: Raito Engineering Corp., TaiwanCreep induced tunnel collapse during construction – a case study of a mountain railway tunnel in Taiwan1450 The mountain railway No. 42 Tunnel once collapsed during construction when only the primary shotcrete lining was in place. According to geological analysis and excavation records, the major cause of disaster was presumably due to time-dependent behavior of rock. In order to elucidate the impact of creep-induced displacement during excavation, a simulation-based methodology, i.e. a viscoplastic model combining the two-component power model and the ubiquitous-joint model, is proposed. The time dependent parameters were calibrated using the back analysis from the convergence measurement data. The modelling results have illustrated that the excavation induced displacement can be dissociated into two parts, the instantaneous deformation due to stress relaxation, and the time dependent deformation due to creep. The overall study in terms of current findings has shown that our proposed model is a useful tool for investigating long term stability of tunnels surrounded by creep potential rock material. | viscoplastic model, creep behavior, convergence, tunnel excavation
T16: Underground storage for liquid and gaseous mediaPhilippe VASKOU (1), Nicolas GATELIER (2)1: University of Cergy-Paris, France; 2: Geostock, Rueil-Malmaison, FranceWhat can be the future of underground storages in the context of green energy? - Geomechanical aspects1452 Compressed hydrogen is classically stored in steel overground tanks. Large underground storages of compressed hydrogen are extremely few whereas the challenge today is storing liquified hydrogen at very low temperature (cryogenic). Salt caverns are used for storing compressed hydrogen in gaseous state since the 1970s but suitable salt environments are limited and heterogeneously distributed, worldwide. Thus, storing compressed hydrogen in lined rock caverns (LRC) similar to compressed natural gas (CNG) is now envisaged. Currently there is only one example of LRC for storing CNG in operation and no compressed hydrogen rock cavern has been designed yet at an industrial scale. Regarding geomechanics, the conversion of salt caverns is relatively easy but more difficult for rock caverns, due to the required steel membrane and the quality of the host rock mass. The main design criteria and preliminary geomechanical modelling required for cavern creations and challenges for the conversion are also discussed. | hydrogen, storage, cavern, salt, conversion
T15: Rock and rock mass propertiesAbbas TAHERI (1), Roohollah SHIRANI FARADONBEH (2)1: Queen's University, Canada; 2: Curtin University, AustraliaFailure response of rocks under different cyclic loading histories1453 The post-failure instability of rocks was investigated through an extensive experimental study under four different loading histories, including the monotonic quasi-static loading, single-level systematic cyclic loading (SLSCL), multi-level systematic cyclic loading (MLSCL), and post-peak cyclic loading (PPCL). The lateral strain-controlled and double-criteria damage-controlled testing methodologies were implemented for the experiment. A combined post-peak Class I-II behavior to different extents was detected for soft to strong rocks, while the unstable fracture propagation was more dominant for stronger rocks under monotonic loading. Additionally, rocks exhibited more self-sustaining behavior under MLSCL history with increasing the number of cycles before the failure point. On the other hand, the results of the SLSCL tests revealed that rock brittleness reaches its maximum value by applying systematic cyclic loadings at stress levels close to the monotonic strength. However, the effect of post-peak cyclic loading (PPCL) history on the post-failure response of rocks was negligible. | Post-failure, cyclic loading, damage-controlled, lateral strain-controlled
T07: Geological risks and natural hazardsNathalie CONIL (1), Clara MAGHAMI (2), Marwan ALHEIB (1), Philippe GOMBERT (1)1: Ineris, France; 2: Ecole des MinesImpact of climate change on the collapse of shallow mines – feedback from France1454 For many years, Ineris has been conducting research on the impact of climate change on the stability of abandoned mines. In this context, work has been initiated to reference cases of shallow mine collapses. So far, 480 cases have been identified and described. Preliminary analysis of the information gathered shows that 50% of the cases correspond relate to chalk mines, 32% to limestone mines, and 16% to gypsum mines. Two case studies presented in the paper were also analyzed in more detail. Complexity of the water-rock interaction and the importance of studying more precisely the various parameters impacted and their relationships are highlighted. Therefore, a chalk mine located in Seine-et-Marne (France) was instrumented to monitor the evolution of the structure over time and analyze the different causes of degradation. The objectives are to better understand the behavior of these structures to be able to detect precursor signs to these collapses. | shallow abandoned mines, aging, collapse, climate change, water-rock interaction
T15: Rock and rock mass propertiesYun ZHAO (1), Brijes MISHRA (2), Qingwen SHI (3)1: Department of Mineral Resources, Hubei Xingfa Chemicals Group Co., Ltd, Yichang, China; 2: University of Utah, United States of America; 3: Department of Mining Engineering, North China Institute of Science and Technology, Langfang, ChinaSize-dependent and Anisotropic Coulomb failure criterion1455 This paper proposes the size-dependent and anisotropic Coulomb failure criterion to describe the size effect and anisotropy of shale strength. The failure criterion assumes that cracks and bedding planes cause size effect and anisotropy. The failure criterion has six parameters, the cohesion, friction angle, scaling exponent related to crack and bedding plane. The cohesion decreases as rock size increases based on the scaling exponents while the friction angle is independent of rock size. This paper validates the failure criterion from three aspects. Strength data of anisotropic rock is collected from published research. The failure criterion “fits” the collected strength data of anisotropic rock. A bonded-particle model of shale is developed in PFC2D which explicitly includes cracks and bedding planes. The model strength fits well with the failure criterion. Finally, experiments conducted in shale rock validates the hypothesis that the variation of cohesion and friction angle with rock size follows the failure criterion. | Size effect, Anisotropy, Coulomb failure criterion, Griffith theory, Single plane of weakness model
T13: Numerical methods in rock engineeringEdgar MONTIEL (1), Max BLODEL (1), Edjan BUSTAMANTE (2), Esteban HORMAZABAL (1)1: Srk, Chile; 2: Autonoumus University of MéxicoEffect of blast damage on pillars of caving mines1457 This paper presents an assessment in terms of the influence that blast damage can have over rock pillars and the behavior of rock mass using 3D numerical modelling. The utilization of this approach enables the calibration of model parameters and highlights the framework concerning limit loads and deformations that can occur in production drifts, as well as their association with pillar stability. Its relevance becomes substantial during the construction of underground mines and when utilized for decision-making in project design, where the impact of blasting plays a crucial role in achieving high-quality engineering work. | Pillars, Blast Damage, Caving, Numerical Modelling
T09: Long term behaviour of underground structuresKwang-Il KIM, Changsoo LEE, Dong-Keun CHOKorea Atomic Energy Research Insitute, Republic of Korea (South Korea)Coupled thermo-hydraulic-mechanical analysis for a high efficiency high-level radioactive waste repository in South Korea1460 This study analyzes enhancement of disposal efficiency inversely proportional to disposal area based on three design factors for the high-level radioactive waste (HLW) repository such as decay heat optimization, increased thermal limit of buffer, and double-layer concept. If the repository is designed with the optimized decay heat model, the disposal efficiency increases to 2.3 times of the improved Korean Reference disposal System (KRS+). Additional to the decay heat optimization, increasing thermal limit of buffer to 130 °C or using the double-layer concept provides extra 50 % improvement of the disposal efficiency. If the three design factors are applied all together, disposal efficiency can be enhanced to the five times of the KRS+ repository. Rock mass stability analysis indicates that failure of rock is focused at the corner between the disposal tunnel and deposition hole, and rock spalling failure is generated in the wider area if the thermal limit of buffer is increased. | Coupled thermo-hydraulic-mechanical analysis, High-level radioactive waste repository, Disposal efficiency, Rock mass stability
T01: Challenging rock engineering projectsHarald EGGER (1), Marco Giuseppe FODERÀ (1), Gianluca LIUZZI (1), Antonio SPAZIANI (1), Antonio VOZA (1), Daniela BOLDINI (2)1: Galleria di Base del Brennero – Brenner Basistunnel BBT-SE; 2: Sapienza University of Rome, ItalyPerformance of different diameter Double Shield TBMs: experiences from the excavation of exploratory tunnel and main tubes of the Italian lot Mules 2-3 – Brenner Base Tunnel1461 The Brenner Base Tunnel is a 64 km long underground railway connection under construction between Italy and Austria. The project mainly consists of two main one-track tunnels and a central exploratory tunnel 12 m below them. Considering that the three tunnels intersected the same rock masses and fault zones, the paper analyses the scale factor displayed by selected machine parameters in relation to the tunnel diameter, TBM characteristics and rock mass conditions. Final considerations about the performance of the three TBMs, also in the context of comparable case-histories, are addressed. | Brenner Base Tunnel (BBT), Double Shield TBM (DS-TBM), Exploratory Tunnel (ET), Main Tunnels (MT), Key Performance Indicators (KPI), scale factor
T01: Challenging rock engineering projectsVojkan JOVIČIĆ (1), Boštjan VOLK (2), Gregor VESEL (2), Jože RATEJ (2), Markus SCHMIDT (3)1: Faculty of Civil and Geodetic Engineering, University of Ljubljana, Slovenia; 2: IRGO, Slovenia; 3: Boratec, GermanyTunnelling in Slovenian Dinaric karst: challenges and solutions1462 Slovenian Dinaric Karst is an extensive karst area, 800 km long and up to 150 km wide, which is distinguished by large, closed planes, and variety of relief forms, deep caves, underground rivers, and karst springs. The main challenge for the construction of new Divača-Koper railway line that runs through Slovenian Dinaric Karst is the construction of two seven kilometers long tunnels T1 and T2. Due to scarcity of water resources in the area adequate measures for tunnel construction had to be developed to ensure the sustainability of water resources in the long term. The paper presents experience that was assembled in detection, evaluation and categorization of karstic phenomena that was encountered during the construction of tunnel T1. The temporary and final remedial measures of typical karstic features are presented in the paper highlighting the stability, functionality, and sustainability issues, which were subject to design evaluations and solutions. | tunneling, karst features, remedial measures, sustainability of water resources
T04: Deep mining and tunnellingFedilberto J. GONZALEZ (1), Peter K. KAISER (2), Mark S. DIEDERICHS (1)1: Queen's University, Miller Hall, Kingston, Ontario, K7L 3N6, Canada; 2: Laurentian University, Sudbury, Ontario, P3E 6H5, CanadaDisplacement and energy demand imposed by rapid bulking and tunnel shape change1463 In burstprone ground, sudden and violent failure of hard brittle rock dynamically loads and deforms ground support. Failure of underground excavations comprises two processes: bulking of stress-fractured rock and shape changes of the excavation in response to the fracturing process. For demonstration purposes, a case with a stress ratio k less 1 is examined. Brittle failure of sidewalls occurs if induced stresses exceed the crack propagation stress level, leading to a rupture process and rock mass convergence in which the bulking rock moves rapidly toward the excavation. At the same time, the roof and floor converge rapidly induced by the sudden shape change due to wall rupture. This article presents estimates of kinetic energy demands that would be imposed on support by self-induced strainbursts and associated sudden and violent shape change. The effects of confining pressure at the tunnel surface on the violence of this process are explored using FLAC. | Rapid bulking, self-induced strainburst, shape change
T04: Deep mining and tunnellingMrityunjay JAISWAL (1), Resmi SEBASTIAN (1), Ravibabu MULAVEESALA (2)1: Department of Civil Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab, India, Pin; 2: Centre for Sensors, iNstrumentation and cyber-physical Systems Engineering (SeNSE), Indian Institute of Technology Delhi, Hauz Khas, New DelhiModulated thermal wave imaging approach to detect subsurface microcracks and their coalescence in deep mines for rock burst (strain burst) prediction1465 Rock burst, which is exceptionally powerful and abrupt, is one of the most dangerous geological hazards in deep mines. Although it is difficult to prevent rock explosions, it can be predicted with continual monitoring. Traditional monitoring systems produce a large quantity of data and false signals. Most methods are affected by blasting and other mining activities. This study used modulated thermal wave imaging to locate the high damage zone in a rock sample containing artificially implanted subsurface microcracks prior to any rock bursting. Finite element (FE) simulations were used to examine the infrared thermal response of a rock sample to a fixed-frequency sinusoidal heat wave. To automate detection, a cutting-edge deep-learning technique was used to identify, localize, and segment cracks. A sizable dataset of images with a resolution of 640×480 was produced for the algorithm training and validation. The F1 score and precision of the applied method were considerably high. | Rockburst, thermal monitoring, infrared thermography, deep learning
T17: Rock slope engineeringMiosoty BAUTISTA (1), Juan Carlos COBIAN SALAS (1), Jessica LOPEZ (1), Neil BAR (2), Niccolò COLI (3), Francesco COPPI (3), Andreas GAICH (4), Markus PÖTSCH (4), Miriam BAUMGARTNER (4), Alison MCQUILLAN (5)1: Barrick Gold Corporation; 2: Gecko Geotechnics LLC; 3: IDS GeoRadar SRL; 4: 3GSM GmbH; 5: Rocscience IncDeveloping a Digital Twin: A Semi-Brittle Slope Failure Case Study from Pueblo Viejo Gold Mine1467 Technological improvements in geotechnical mapping, modelling and monitoring now allow a digital twin to be developed and maintained in parallel with mining operations. That is, the routine use of aerial photogrammetry, semi-automatic rock mass characterization, three-dimensional slope stability modelling and ground-based interferometric synthetic aperture radar monitoring allow near real-time comparison of modelled and realized ground conditions. This is critical for reconciling the effectiveness of geotechnical models for predicting future slope stability (or instability). This paper presents a semi-brittle slope failure case study from Pueblo Viejo gold mine which was managed using a digital twin approach. The near real-time comparison of the three-dimensional model with observed slope conditions allowed critical structures to be added to the geotechnical model as mining progressed. This led to the identification of a high risk area that would not have been identified if the digital twin was not implemented & maintained during mining. | Slope stability analysis, photogrammetry, radar monitoring, digital twin
T04: Deep mining and tunnellingMax JOHNZT John, AustriaAre trigger levels useful for tunnels at high rock pressure?1468 For rock tunnels under high overburden and/or squeezing ground stable conditions may be obtained at a wide range of displacements depending on the support stiffness and rock mass characteristics. The ground reaction curve (Fenner-Pacher curve) depends on complex geologic and surrounding conditions which may never be known beforehand. It may also be noted, that once the rock mass strength is exceeded, the rock mass curve is changed. This has rarely been noted in the literature. The fracture processes within the rock mass determines if critical situations may occur. Therefore, rock bolting is most important in order to control the development of failure surfaces. As long as displacements tend to cease, a stable condition is approached. Because displacements depend on excavation rate and sequence (heading/bench/invert) as well as on the stiffness of support including deformation slots and/or yielding elements, displacements are not decisive as trigger values. | Rock pressure, trigger levels, fracture process, displacements, monitoring
T01: Challenging rock engineering projectsKarsten THERMANN (1), Raja Bhai SHILPAKAR (2), Bibash PARAJULI (3), Eirinaios CHRISTAKIS (1)1: Tractebel Engineering GmbH, Germany; 2: Tanahu Hydropower Ltd, NEA, Nepal; 3: PowerChina Chengdu Engineering Co. Ltd, ChinaDifficult Ground Conditions demand for an Observational Approach for a Powerhouse Cavern in the Himalayas1469 The powerhouse cavern excavation for Tanahu Hydropower Project (140MW), in Nepal, was successfully completed in July 2022. The site is geologically located in the Lesser Himalayan Zone. During cavern excavation, moderately to highly foliated Slate with phyllitic Slate intercalations and localised sheared zones were encountered. To cope with difficult ground conditions, the design of rock support was not only based on 3D-modelling but rather adopted an observational approach. Thus, during excavation a thorough monitoring system was implemented consisting of multi-point borehole extensometers, load cells, convergence stations and piezometers. Data collection and evaluation of results were conducted on a daily basis during the whole excavation process. Aiming to mitigate occurring deformations during the excavation stage, the rock support measures were modified accordingly. Furthermore, to control overstressing, loads from pre-stressed double-corrosion protected anchors required stress release. The timely response to monitoring results was of paramount importance for the successful excavation of the powerhouse cavern. | observational method, powerhouse cavern, pre-stressed anchors, instrumentation, phyllitic Slates
T01: Challenging rock engineering projectsJohannes JESSEN (1), Jochen FILLIBECK (1), Florian ZAHLER (2), Raphael ZUBER (2)1: Technical University of Munich, Munich, Germany; 2: Weilheim State Building Authority, Weilheim, GermanyPU grouting and sealing measures on the Kramer Tunnel1470 The Kramer Tunnel in the north of Garmisch-Partenkirchen is designed as a single-tube road tunnel with two-way traffic. The tunnel was excavated using NATM. The 3,600 m long tunnel is divided into a pressure-relieved (drained) section and a waterproof (sealed) section, which can withstand pressures of up to 5 bar. Four shotcrete bulkheads were installed to separate the sealed section (rock-slide area) from the drained section. Additionally, PU grouting was employed around the bulkheads to reduce the longitudinal water flow along the main and exploratory tunnels. This article reveals how the radial grout curtains were executed within limestone-marl alternations. Taking the geological conditions into consideration, the success and quality of the grouting work was monitored by water pressure tests and by quantitatively evaluating the grouting records. Construction details concerning the chemical injection material, the grouting equipment and the break-off criteria are discussed. | chemical grouting, grout curtain, bulkhead, break-off criteria
T15: Rock and rock mass propertiesAnjan PATEL (1), Srikanth KANDALAI (1), Nithin Jacob JOHN (1), Shrirang PANDE (2)1: Visvesvaraya National Institute of Technology, Nagpur, India; 2: M/s Standard Precision Testing Laboratory, Khadgaon Road, Lava, Nagpur-23, IndiaEffects of weathering on geotechnical properties of basalt rocks from the Vidarbha region in Maharashtra, India1471 It is well known that the degree of weathering largely affects the geotechnical properties of rocks. Study of rock properties vis-à-vis degree of weathering and the site-specific parameters obtained through recovered rock core pieces during drilling is supposed to be useful for various engineering purpose. A similar effort has been made in the present study. Bore logs data were collected for different sites from Vidarbha region in Maharashtra, India, where basalt rocks are encountered. Based upon field identification, extent of weathering in various rock core pieces collected from different depths in boreholes at different locations was identified along with the determination of RQD value. Further, variation of some rock properties (viz., density, water absorption value, and unconfined compressive strength) with depth was studied. Results obtained from the analysis are presented and discussed in this paper. | Basalt rock, Weathering, Depth, Unconfined compressive strength, Rock quality designation
T07: Geological risks and natural hazardsJohannes BRANKE (1), Jan PFEIFFER (2), Thomas ZIEHER (3), Magnus BREMER (1), Martin RUTZINGER (1), Bernhard GEMS (1), Margreth KEILER (1,2), Barbara SCHNEIDER-MUNTAU (1)1: University of Innsbruck, Innsbruck, Austria; 2: Austrian Academy of Sciences, Innsbruck, Austria; 3: Austrian Research Centre for Forests (BFW), Innsbruck, AustriaClosing the gap from spatio-temporal displacement monitoring to geomechanical process understanding of cascading multi-hazards caused by deep-seated gravitational slope deformations1473 Active deep-seated gravitational slope deformations (DSGSDs) and interlinked secondary processes such as rockfalls and debris flows pose multiple threats to livelihoods in mountain regions. A currently active part (~0.35 km2) of the Reissenschuh DSGSD (Schmirn valley, Tyrol, Austria) shows considerable displacement rates of about 1 m per year. This remarkable relocation of material constantly changes the topography and leads to a pronounced activity of debris flow and rockfall at the landslide toe. This contribution focuses on understanding the interactions of DSGSD activity (rock mass supply) and interlinked cascade dynamics to assess their complex triggering mechanisms and related secondary processes. It gives an overview of previous and ongoing monitoring campaigns and presents preliminary findings on cascade process interactions. | Natural hazard research, deep-seated gravitational slope deformation, cascade multi-hazard, landslide
T01: Challenging rock engineering projectsAndrew SHIELS (1), Marc MPOYO (2), David BECK (3), Sevda DEHKHODA (4)1: Glencore Copper, Brisbane, Australia; 2: Kamoto Copper Company, Kolwezi, DRC; 3: Beck Engineering Pty Ltd, Sydney, Australia; 4: Beck Engineering Pty Ltd, Brisbane, AustraliaSimulating global deformation and assuring ongoing stability in a complex multi lode room and pillar mine1475 A widespread series of pillar failures occurred at the Kamoto Copper Mine in the early 1990’s. Access to the affected areas was lost and an extended period of mine closure followed. To constrain interaction between the past failure and future work areas, the current mine required careful considerations and interactions with the failed zones, and a barrier pillar has been retained to protect the future work areas from effects of the past failure. A system of access pillars and stabilization pillars and staging of extraction works to shape deformation, manage stress, and allow a sufficient degree of control over stability has been implemented. Mine stability is maintained through an ongoing process of engineering design, simulation, observation, and analysis for a mine with a complex system of pillars, which is described in this paper. | Room and pillar, global stability, pillar failure, observational programme
T07: Geological risks and natural hazardsMaria Lia NAPOLI (1), Monica BARBERO (1), Marta CASTELLI (1), Francesco CASTELLI (2)1: Politecnico di Torino, Italy; 2: Università degli studi di Enna "KORE"An approach to assess the detachment propensity of rockfall source areas: the Susceptibility Index to Failure (SIF)1476 This paper proposes a practical approach to assess the susceptibility of rock slopes to produce rockfalls. Once identified the potential release areas, a rockfall Susceptibility Index to Failure (SIF) can be assigned to distinguish among prone areas with detachment propensity from 0 (null probability) to 1 (maximum probability). This index can be defined according to the presence and intensity of several causative factors, which were identified and scored on the basis of the scale of interest and the environment considered. Specifically, the small and the detailed scales and the mountain and coastal-marine environments were considered. An application example is presented to illustrate the validity of the proposed approach. | rockfall, detachment propensity, causative factors, Susceptibility Index to Failure (SIF), susceptibility maps
T01: Challenging rock engineering projectsSailesh ADHIKARI (1,2), Krishna Kanta PANTHI (1), Chhatra Bahadur BASNET (2)1: Norwegian University of Science and Technology, Norway; 2: Pashchimanchal Campus, Tribhuvan University, NepalStability issues associated with the construction of underground caverns of Super Dordi Hydropower Project, Nepal1477 The rock mass is heterogeneous and makes underground space construction a challenge to engineers. The rock formation, mineralogical composition, degree of schistosity, and weathering, are the major factors that determine the stability condition and rock support requirements. This manuscript deals with the stability situation of the underground settling basin caverns of Super Dordi Hydropower Project (SDHP) in Lamjung district of Nepal which is located at the lower boundary of the Higher Himalayan rock formation. The two parallel underground settling basins are 120m long and have an approximate cross-sectional area of 113 sq. m. The manuscript further discusses geological and rock mass quality conditions and evaluates the stability of the underground settling basins using 2D numerical modeling. The outcomes of the analysis presented in the manuscript have been helpful for the optimization of applied rock support. | Underground Space, Rock Support, Settling Basin Caverns, Super Dordi Hydropower
T15: Rock and rock mass propertiesYota TOGASHI (1), Riho HIRASAWA (2), Masahiko OSADA (1)1: Saitama University, Japan; 2: Saitama University (presently Oriental Consultants), JapanA new simple shear test of rock prism specimen by torsional shearing1478 This study proposes a new simple shear test method by torsional shearing of rock prism specimens. In this test, multiple radially placed prismatic specimens are torsional sheared under normal load. To validate the test method, a torsional loading apparatus capable of carrying 50 kN normal load and 300 kN cm torque was prepared, and the proposed test was conducted using prismatic mortar specimens which strength are equivalent to soft rock (UCS less 25 MPa). The size of the prismatic specimen is 20 mm height, 20 mm width, and 70 mm depth. The stress-strain characteristics of the mortar specimens were consistent with the previously conducted trends in uniaxial compressive and tensile strength. Peak shear stress in simple shear tests at under 0.9 MPa normal stress conditions equals tensile strength. Almost equal tensile strength was obtained when compared to the results of the proposed test. | Simple shear, prismatic specimen, torsional shearing, soft rock
T12: New developments in rock supportDanqi LICurtin University, AustraliaAn analytical model for cable bolts considering crack propagation in grout1480 Understanding the mechanical behaviour of cable bolts under axial loading from analytical perspective is essential and economic for selecting the most appropriate cable bolt for a specific scenario and also the ground support system design. This study develops a novel analytical model coupling the crack propagation in the grout annulus to capture the load-displacement performance of cable bolts under axial loading. The majority of the input parameters associated with mechanic properties of the cable bolt and grout are readily determinable by laboratory tests. At the end, the capability of the proposed model to simulate the performance of cable bolts under axial loading is demonstrated by validating against experimental results in the literature. | Analytical model, Cable bolts, Pull out test; Crack propagation
T05: Digitalization & AutomatisationAli BONAKDARIndividual private geomechanical advisor, Tehran, Islamic Republic of IranIntroducing a new cloud computation paradigm for rock engineering problems based on XaaS Model and the proposed A4 Framework1481 Nowadays, High Performance Computing (HPC) is being used as one of the most interesting topics in both aspects of scientific and practical, relies on recent special and exquisite developments in software architectures and frameworks and also hardware improvements in distributed networks over the Internet. As a geo-engineering problem to be solved, there are some limitations against today single-node commercial applications, containing runtime, analysis costs, scale, and accessibility. In this research, a new paradigm has been proposed base on a new developed framework (A4) and XaaS model. Using the new paradigm, significant modifications will be applied in computation runtime, decrease in computation costs, high software accessibility, in addition to scalability and diversity of problem solving. An online web-based 3D visualization platform (containing pre-processing and post-processing of numerical modeling) has been implemented to remove the limitations of the available single-node conventional applications to enable them running on a simple Internet browser with an affordable cost. | Cloud Computation, High Performance Computing (HPC), Distributed Computation, Parallel Numerical Analysis, Computation Farm, Web 3D Visualization
T04: Deep mining and tunnellingMiguel Angel BERROCALGEOMECANICA DEL PERU EIRL, PeruIn situ stress evaluation according to the Drillhole detonation method, applied to the geometric design underground excavations1482 The rock mass is composed of homogeneous and heterogeneous rocks, generating stresses of different orientation and magnitude. One of the techniques to evaluate the state of stress in situ is the Drillhole detonation method; the procedure consists of detonating a drillhole with explosives to obtain radial cracks and with this result analyze the ellipse generated, called stress ellipse. The data to evaluate the magnitude of the stresses σ1, σ3, and σ2; are based on the analysis of the stress ellipse, from which are obtained: the orientation (α) of the major stress σ1, the coefficient k, and the Correction factor (CF). The Drillhole detonation method provides the appropriate technique for the design of underground excavations, according to the profile of the horizontal and vertical trend stress ellipse. | K coefficient, Design of underground excavations, Drillhole detonation method, In situ stress evaluation, Stress ellipse
T06: Geological investigation and characterizationYong-Zhi HUANG, Tai-Tien WANG, Fu-Shu JENGDepartment of Civil Engineering, National Taiwan University, Taipei, TaiwanA study on point cloud interpretation of fracture intensity and its spatial variability1484 In geological surveys with a rock engineering focus, the investigation and description of discontinuities is an important but time-consuming and labor-intensive step. With advances in surveying and mapping technology, digital surface models (DSM) and their corresponding point clouds can reproduce the geometric properties of outcrops, and provide a useful intermediary for rock fracture investigations. Here we develop and apply a method for fracture mapping that employs a discontinuity set extractor (DSE) program to capture fracture planes from point clouds and a spherical scan approach to determine fracture intensity in a direction-dependent fashion. The proposed approach is applied to obtain the fracture intensity of six outcrops, and the spatial variation of fracture intensity and corresponding influencing factors are investigated accordingly. The fracture intensity has both heterogeneous and directional-dependent characteristics. Their variations are affected by lithology and folds. | Fracture intensity, Spatial variability, Advance surveying and mapping, Point cloud interpretation
T09: Long term behaviour of underground structuresArash BARJASTEHKhuzestan Water & Power Authority (KWPA), Islamic Republic of IranGeological control on the operational behavior of Masjed -e Soleyman Dam, Iran1485 This article is aimed at study the role of geology on the recent behavior of Masjed-e Soleyman (Godar-e Landar) Dam in Khuzestan Province, south west of Iran. The dam which is a rock fill type has a height of 177 m with a 230 million-m³ reservoir. The foundation rock of the dam is composed of sandstones and conglomerates. Andeka active fault in the north of the dam site is a major structure that affected the dam site geology. Recent monitoring data indicated that powerhouse and transformers caverns suffer severe high stresses on their roofs due to swelling of a claystone layer atop the caverns. Excessive rock mass displacements which caused shotcrete cracking and bolt failure can be seen in some parts of the powerhouse cavern. This article discusses the possible relationship between the geological setting and the observed problems with special emphasis on the powerhouse cavern. | Operational behavior, geologic structure, lithology, Andeka Fault
T03: Deep geothermal energyArno ZANG (1,2), Hannes HOFMANN (1,3), Gergö HUTKA (1,2), Bakul MATHUR (1), Mauro CACACE (1), Serge SHAPIRO (4), Beau WHITNEY (5), Cedric DUVAIL (5), Ramon Secanell GALLART (5), Niels GROBBE (6), Annemarie MUNTENDAM-BOS (6)1: German Research Centre for Geosciences GFZ, Germany; 2: Institute of Geosciences, University of Potsdam, Germany; 3: Institute of Applied Sciences, Technical University of Berlin, Germany; 4: Institute of Geosciences, Free University of Berlin, Germany; 5: Fugro NL Land BV, Groningen, The Netherlands; 6: Dutch State Supervision of Mines, The Hague, The NetherlandsStress and seismicity related to cooling of geothermal wells1486 Deep geothermal energy (~3-6 km depth) is a candidate for sustainable and carbon-free energy supply. One of the main concerns of deep geothermal systems is induced seismicity that may produce earthquakes of economic concerns, challenging the development of this form of alternative energy. So far, cold water injection has been overlooked but may contribute to induced seismicity due to fault reactivation through thermal stresses also beyond the cooling region. This can be of importance, in particular, in fractured and faulted geothermal reservoirs. In this study, we first compare different approaches to estimate induced seismic risk from slip-tendency analysis, rate-and-state friction theory and modified Gutenberg-Richter statistics based on frictional Coulomb-stress perturbations. Then, we systematically investigate effects of both, intrinsic geological parameters (e.g., fault-, host rock properties and in-situ stress), and operational parameters (e.g., well geometry and placement, injection schemes, induced pressure perturbation) on induced seismicity. | Coulomb failure stress, deep geothermal energy, induced seismicity, rate-and-state friction theory and thermo-hydraulic-mechanical modelling
T11: NATM versus TBMHoyoung JEONG (1), Yudhidya WICAKSANA (2), Sehun KIM (3), Seokwon JEON (3), Jeong-Gi UM (1)1: Pukyong National University, Republic of Korea (South Korea); 2: Bandung Institute of Technology, Indonesia; 3: Seoul National University, Republic of Korea (South Korea)Cutting performance evaluation of Actuated Disc Cutting by linear cutting test1493 This paper presents an investigation into Actuated Disc Cutting (ADC). The ADC is based on the undercutting mechanism and involves several cutting parameters. To enable an experimental analysis of ADC, a new lab-scaled rock-cutting system is introduced. This system facilitates the undercutting concept of rock cutting based on the traditional Linear Cutting Machine (LCM) system. The cutting parameters in ADC, such as eccentricity, linear velocity, and RPM are simulated by the introduced cutting system. The paper also introduces calculation methods for cutter forces and specific energy of ADC based on the system. A series of undercutting tests were performed on a designed hard rock specimen under different cutting conditions. The effects of cutting parameters on cutter forces and specific energy were discussed, and the optimal cutting conditions in ADC were analyzed. The proposed lab-scaled rock-cutting system and calculation methods can be utilized for future studies in this field. | Actuated disc cutting, undercutting, LCM, Cutting efficiency
T13: Numerical methods in rock engineeringAmichai MITELMAN (1), Beverly YANG (2), Davide ELMO (2)1: Ariel University, Israel; 2: University of British Columbia, Vancouver, CanadaA Surrogate Model for Automating Slope Stability Analysis1494 Owing to the advancements in the field of machine-learning (ML), the prospects of coupling ML with engineering analyses are currently being realized for various applications. Such applications can be particularly useful for geological engineering, where the ground properties are heterogeneous and hard to estimate accurately. In this regard, surrogate models are being increasingly used as tools to accelerate learning for both research and practical applications. In this paper, we describe the application of a surrogate model for the analysis of a slope stability problem using the limit equilibrium slice method. For setting up the surrogate model, two primary stages are required: 1) artificial data generation, where numerous results are computed, and: 2) data learning, where ML is used for building the correlation between the problem inputs and results of interest. Through this relatively simple example, we demonstrate how routine engineering tasks can be readily automated. | Surrogate models, Machine-learning, Slope stability, Probability of failure
T15: Rock and rock mass propertiesManuel WINKLER, Thomas FRÜHWIRT, Thomas MARCHERInstitute of Rock Mechanics and Tunnelling, TU Graz, AustriaA theoretical framework for calibrating the transversely isotropic elastic rock parameters from UCS tests on cylindrical specimens using circumferential strain measurements1496 The standard method for determining the set of five independent elastic constants of transversely isotropic rocks relies on the conduction of at least three UCS tests with directional radial strain measurements on samples with varying isotropy plane orientation. However, in many cases only averaged values for the lateral strains are available from chain extensometer measurements as commonly carried out in rock mechanics laboratories. Such measurement setups disregard the anisotropic deformational behavior of transversely isotropic rock samples which appears as a result of non-horizontal isotropy plane orientations. A direct utilization of averaged radial strains in the determination of the five independent parameters without further considerations is thus not possible. In this paper a possible scheme for the inclusion of circumferential strain measurement information in the determination of the elastic constants of transversely isotropic rocks based on UCS tests carried out on three samples with varying isotropy plane inclinations is presented. | UCS tests, transverse isotropy, elastic parameters, circumferential strain measurement, Poisson’s ratio
T12: New developments in rock supportFrederick KUHNOWGEI ConsultantsBlast Induced Vibrations and Strain Rate Effects in Dynamic Capacity of Underground Concrete Structures1498 When performing blasting operations in open pit mines, large amounts of energy is released and transmitted through the rock. The energy released can have significant impacts on mining operations and can adversely affect the mine production. This technical paper presents recommendations for blast design to prevent damage from blasting on underground concrete structures. Emphasis is placed in vibrations generated by blasting and its effects are studied referring to an existing hard rock mine expansion and asks whether production blasting would damage adjacent underground concrete structures due to blast stress waves. A set of criteria was developed to implement when blasting near-by underground structures. Knowledge of particle velocity and wave propagation theory for site-specific conditions to determine a safe level of vibration was recommended. The results suggest that an increase in structural capacity (dynamic capacity) is expected when structures are subjected to loads at very high strain rates, such as those of blasts. | Blasting loads, wave propagation velocity, peak particle velocity, earthquake loads, dynamic capacity, underground structures
T07: Geological risks and natural hazardsPai-Chiao LO (1), Wei LO (2), Yong-Zhi HUANG (1), Ya-Chu CHIU (3), Tai-Tien WANG (1), Yu-Chung HSIEH (4)1: National Taiwan University,Taipei, Taiwan; 2: National Taipei University of Technology, Taipei, Taiwan; 3: National Chung Hsing University,Taichung, Taiwan; 4: Central Geological Survey, New Taipei, TaiwanSlope stability and engineering characteristics of rock mass at the boundary of slate and schist: Study of Southern Cross-Island Highway in southeastern Taiwan1500 The slopes in the study area had suffered from frequent collapses. To investigate the relationship between slope instability and the engineering parameters of the rock masses at the boundary of slate formation and Tananao schist formation, interpretation of the spatial distribution of collapses from multi-temporal remote sensing images, investigation of slope instability mechanism, surveying and geological mapping, and evaluation of engineering parameters of rock masses have been performed and reported in this article. The outcomes indicate that the Q values of the rock masses at the boundary of slate and schist are lower than those of the surrounding rocks, resulting in areas prone to rock slides, debris slides, and rock fall. The adaptive structures, such as axial faults, pre-existing shear, and dense fractures near the axis of a mesoscale fold, cause rock fragmentations, which are often the source of rock debris and rock fall. | slate, schist, landslide, slope instability, fold
T15: Rock and rock mass propertiesRoberto TOMÁS (1), Miguel CANO (1), Luis F. PULGARÍN (1), Vicente BROTONS (1), David BENAVENTE (1), Tiago MIRANDA (2), Graça VASCONCELOS (2)1: UNIVERSIDAD DE ALICANTE, Spain; 2: ISISE, Departamento de Engenharia Civil. Universidade do Minho, PortugalPhysical-mechanical properties of a granite used in the UNESCO World Heritage of the north of Portugal after high-temperature pretreatment1501 This paper studies the evolution of physical and mechanical properties of 46 cubic samples of a granite widely used in the UNESCO World Heritage of the north of Portugal pre-treated at different temperatures (between 105 and 700 °C) and cooled under different conditions (i.e., air-cooled and water-cooled). The results showed that specific gravity and mineralogy did not exhibit significant changes after the thermal pre-treatment. In contrast, density, porosity, ultrasonic properties, uniaxial compressive strength and elastic modulus showed important variations, mainly at temperatures higher than 500 ºC. The SEM analyses clearly show an increase in the density of cracks, as well as in the width and length of the cracks from 500 ºC. Furthermore, it was observed an amplification of the damage in those samples cooled by water immersion. These results are of relevance for the evaluation of the integrity level of buildings built using this rock after a fire. | thermal effect; physical properties; uniaxial compressive strength; elastic modulus; granite; cultural heritage
T15: Rock and rock mass propertiesJun ZHU (1), Jianhui DENG (2)1: Key Laboratory of Mountain Hazards and Earth Surface Process, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences (CAS), Chengdu,China; 2: College of Water Resources and Hydropower, Sichuan University, Chengdu, ChinaThe combined effects of water saturation and strain rate on crack initiation and damage stress of rock1504 Here, we reported a series of uniaxial compression and acoustic emission (AE) tests performed on dry and saturated marble at different strain rates, which offer new information on the combined effects of water saturation and strain rate on its crack initiation CI stress and crack damage CD stress. The test data show that the water saturation causes various reductions in the ratio of CI stress to peak stress NCI, while increments in the ratio of CD stress to peak stress NCD. This NCI reduction is due to the main water-weakening effect of pore water pressure, and the increase in NCD is caused by the additional vicious effect. The NCI of saturated marble shows a decreasing trend with increasing strain rates, while that of NCD remains nearly constant. By easily initiating more small defects, the strain rate effect can strengthen the NCI reduction and inhibit the NCD increase. | stress threshold; water saturation; strain rate; acoustic emission; dominant frequency
T17: Rock slope engineeringNurkhair TELEU, Neil BAR, Herman ZLOBIN, Philipp MOHRKAZ MInerals, KazakhstanRock slope design and residual risk management for Aktogay Copper Mine, Kazakhstan1507 Aktogay is a large open pit copper mine in Kazakhstan. Several geotechnical investigations have been completed from initial scoping and feasibility studies to continuous improvement studies during mining. Rock slope design has involved several phases of stability analyses for various stages and the life-of-mine open pit. With the progression of mining in the pit, ground conditions at the mine are becoming more apparent and uncertainty is progressively reduced. This paper briefly describes the slope stability modelling approaches used to understand and communicate geotechnical risks and opportunities for integration with a complex mine plan and sequence. A combination of 3D limit equilibrium and finite element analysis was incorporated into slope stability assessments for future slope excavation stages. The models have been developed with the intention of being digital twins to actual mine progression, with routine updating as engineering geological features are validated and updated with new exposures and additional site investigations. | 3D slope stability analysis, risk management, digital twin, mining
T12: New developments in rock supportDorna EMAMI (1), Souvik SAHA (2), Mehdi SERATI (1), Harry ASCHE (3), David J WILLIAMS (1)1: The University of Queensland, Australia; 2: University of Queensland – IIT Delhi Academy of Research, New Delhi, India; 3: Aurecon, Brisbane, AustraliaOn The Expected Location of Fire-Induced Concrete Spalling1509 The occurrence of fire-induced spalling in concrete structures and shotcrete elements (aka sprayed concrete) is influenced by various factors including the type of heat and applied fire curves, temperature gradient, sample size, and quality and mixture of the concrete. Predicting the location of spalling can significantly assist with developing fire resistance tests to allow for the correct placement of instrumentation and monitoring equipment such as temperature and pressure sensors, high-speed cameras, and 3D/2D Digital Image Correlation imaging, among others, in optimal positions to be able to closely monitor the spalling process. This study examines the data from tests previously carried out to generate a model for predicting the location of fire-induced spalling in concrete samples, and then compares it experimentally to validate the proposed model. The results indicate good compatibility between the data from literature and the performed experiments. | Fire-induced Spalling, Spalling Positions, Pressure, Temperature
T01: Challenging rock engineering projectsMario HEIN (1), Zafer EKICI (2), Christine PEINTNER (2), Robert HOLZER (1), Thomas HOFMANN (3)1: Geoconsult Wien ZT GmbH, Austria; 2: IGT Geotechnik und Tunnelbau, Austria; 3: ÖBB Infrastruktur AG, PL Semmering Basistunnel, AustriaSemmering Base Tunnel – Geotechnical challenges at crossing a fault system in combination with high water pressure1511 The Semmering Base Tunnel (SBT), one of the major infrastructure projects in Europe is part of the Baltic-Adriatic railway corridor and connects the two federal states of Lower Austria and Styria. Due to its total length of 27.3 km and complex rock mass conditions, the project is divided into 3 construction lots. The eastern construction lot SBT 1.1 Gloggnitz Tunnel crosses major fault zones adjacent to water-bearing carbonatic rocks (Grassberg), with a potentially high water inflow in combination with high water pressure. Crossing the fault system north of the Grassberg is one of the biggest challenges of lot SBT 1.1, due to the poor rockmass quality within the fault system and 10 bar water pressure within the Grassberg. Systematic probe drillings indicated a complex sequencing of geological units at the transition from the fault zone into the water-bearing Grassberg unit and required a modification of the original design approach. | Semmering Base Tunnel, grouting, monitoring, high water pressure, high permeability
T13: Numerical methods in rock engineeringAsif Jeelani BHAT, Dr vidya Bhushan MAJIIndian Institute of Technology Madras, IndiaOptimum spacing of TBM disc cutters using an explicit finite element approach1512 One of the major challenge in the production of TBMs is the design of the cutter-head. The main element affecting cutting efficiency is the choice of an adequate cutter spacing. Even a minor departure from the ideal spacing causes a decrease in cutting effectiveness. In this study, to model optimum cutter spacing, numerical tests are carried out. The three-dimensional dynamic failure seen in tests of the linear cutting machine (LCM) is simulated using LS-DYNA software. For the purpose of simulating the process of rock failure, we use a constitutive model based on the extended Drucker-Prager strength criterion and the Johnson-Holmquist-2 (JH-2) material model. The specific energy is obtained by the rolling force acting on the TBM disc cutter and the mass of rock debris obtained during the numerical test. The optimal cutter spacing calculated by numerical simulations agrees well with that established by LCM tests. | TBM, Disc cutter, Specific energy, Optimum spacing, LS-DYNA
T09: Long term behaviour of underground structuresChunping WANG (1), Liang CHEN (1), Jian LIU (1), Xingguang ZHAO (1), Ju WANG (1), Jianfeng LIU (2)1: Beijing Research Institute of Uranium Geology, Beijing, China; 2: Sichuan University, Chengdu, ChinaExperimental study and damage-mechanism-based modelling of creep behavior of fractured granite1513 Experimental investigations on creep behavior of fractured granite have been performed under multi-step stresses. The significant stress effect on the creep strain rate is presented. A coupling damage of the initial macroscopic damage of fractured granite and the microscopic damage induced by external load is deduced. A damage-mechanism-based creep model for fractured granite has been proposed by introducing the damage evolution in the constitutive relations. The model parameters are determined by fitting the experimental results of the time-dependent deformation of fractured granite. It is indicated that the creep constitutive model proposed can provide a precise description of the full creep process in fractured granite under different stresses. The Burgers model is indicated to be a special case of the damage-mechanism-based creep model. | Fractured granite, creep model, damage, fractional derivative
T06: Geological investigation and characterizationMaria Lia NAPOLI (1), Lorenzo MILAN (1), Monica BARBERO (1), Edmund MEDLEY (2)1: Politecnico di Torino, Italy; 2: Terraphase Engineering, Oakland, CA, U.S.AApplication of the point counting technique for estimating the VBP of geotechnically complex formations (bimrocks/bimsoils)1514 The estimation of the Volumetric Block Proportion (VBP) of geotechnically complex block-in-matrix formations (such as melanges) is crucially important for reliable predictions of their mechanical behavior, and for reducing safety risks and extra costs caused by unexpected technical problems that can occur during excavation/construction works. However, estimating site-scale VBPs is extremely difficult. This paper describes a statistical investigation of virtual block-in-matrix models to determine the amount of bias introduced when the point counting technique is used to infer VBPs from in-situ 0D (point) measurements (PBP). A graph is provided to obtain an uncertainty factor (UF) to adjust the measured PBPs to real VBPs, on the basis of the block content measured and the size of the area analyzed. To validate the approach, the results are compared to those provided recently by Napoli et al. (2020), where the uncertainty in estimates of VBPs from 2D measurements was investigated. | Bimrocks, bimsoils, point counting technique, volumetric block proportion (VBP), uncertainty factor, statistical analysis
T13: Numerical methods in rock engineeringLeandro Lima RASMUSSEN (1,2), Ki-Bok MIN (2)1: University of Brasilia, Brasilia, Brazil; 2: Seoul National University, Seoul, Republic of KoreaA 3D breakable Grain-Based Discrete Element model for transversely isotropic rocks1515 This research proposes a novel Grain-Based Model (GBM) for the simulation of transversely isotropic rocks. The model introduces Rigid Body Spring Network bonds and a fictitious stress approach into the Discrete Element Method in order to generate the anisotropic elastic behavior and utilizes breakable particles to manifest cleavage failure. The new model is verified by comparing numerical stress bulbs from a point load analysis against a finite element solution and by comparing unconfined compression strength test results from Asan Gneiss GBM against Jaeger’s 'plane of weakness' theory. Of note, the novel grain-based model allowed the direct determination of macroscale anisotropy in elastic and strength properties without the need for trial-and-error calibrations of input parameters. In addition, the proposed breakable grain scheme provided for realistic representations of the failure modes usually observed in rocks with cleavage. | Hybrid LDEM, RBSN-DEM, Transversely isotropic rock, Breakable particle
T17: Rock slope engineeringMiguel CANO (1), José Luis PASTOR (1), Roberto TOMÁS (1), Adrián RIQUELME (1), Luis JORDÁ (2), José SERÓN (3)1: University of Alicante, Spain; 2: Universidad Politécnica de Madrid, Spain; 3: Universitat Politècnica de València, SpainA critical look to the practical use of Rock Mass Rating (RMR) and Slope Mass Rating (SMR)1517 RMR and SMR are two of the most applied classifications for tunnels and slopes, respectively, excavated in rock masses. Five parameters are used to compute the basic RMR classification for each discontinuity set. However, it is not clarified the whole Rock Mass RMR value. Here, the rock engineering community interprets the possibilities of calculating RMR in different ways. In addition, given that SMR is calculated from RMR by adding four correction factors, different interpretations arise. In this work, different cases of rock masses were analysed and both indexes, RMR and SMR, were assessed using different interpretations of RMR calculations. From this analysis, it can be concluded that, occasionally, there is a significant difference in the RMR and SMR values obtained depending on the followed procedure. | RMR, SMR, rock engineering, interpretation criteria, critical look
T16: Underground storage for liquid and gaseous mediaSasan MORAVEJ (1), Mehdi SERATI (1), Mojtaba BAHAADDINI (2), David WILLIAMS (1)1: The University of Queensland, Australia; 2: Shahid Bahonar University of Kerman, IranThermomechanical Behaviour of Rock Salt1518 The stability and integrity of salt caverns are critical for ensuring their safety and long-term viability, especially when used for storing hydrogen on large scales. This study is aimed at understanding the failure mechanisms of rock salt under coupled thermo-mechanical stress regimes based on the study of rock salt dilatancy-compression boundary stress levels. Several tests were conducted using a high-temperature true triaxial testing facility on 50 mm high-purity rock salt cubes. Different temperatures of 30 °C and 100 °C were considered, along with a variety of stress values of 0, 5, 10, and 20 MPa for confining pressures. The results showed that the applied deviatoric stress and temperature both have significant coupling impacts on the peak strength and dilatancy boundary of rock salt. | Salt cavern, Dilatancy boundary, peak strength, intermediate principal stress, high temperature
T16: Underground storage for liquid and gaseous mediaLukas BAUMGÄRTEL, Feline KÖRNERLeibniz University Hannover, Hannover, GermanyThe fracture behavior of rock salt under present gas pressure in mechanical extension experiments1519 The storage of large quantities of energy sources (e. g. natural gas or hydrogen) in rock salt caverns has regained particular importance in today's world. Therefore, the geomechanical design of caverns in rock salt formations is necessary to ensure a safe but also economic operation. Special attention has to be paid to the gas withdrawal phases and the processes resulting for the surrounding rock mass. When the stresses inside the rock fall below the internal gas pressure, effective tensile stresses can cause the development of infiltration fractures. A special triaxial cell was developed for the laboratory study of such stress states in rock salt. Cylindrical hollow rock salt test specimens are loaded mechanically with an axial, circumferential and internal gas pressure. The axial stress reduction leads to a rupture at different stress differences between axial and gas pressure which shows dependencies on the initial pressure state and temperature. | energy storage, rock salt cavern, infiltration fractures, laboratory testing
T04: Deep mining and tunnellingMohammad MOHAMMADI, Johan SPROSSDivision of Soil and Rock Mechanics, KTH Royal Institute of TechnologyModeling uncertainty of activity duration in probabilistic time estimation of tunneling projects1520 The PERT distribution may be a suitable distribution for modeling activities’ duration in probabilistic time estimation of tunnel projects as it puts more emphasis on the mean value of the distribution. In this paper, we compared the outcome of time estimations for a tunnel, using the triangular and PERT distributions for modeling the uncertainty of activities’ duration. The results indicate that the choice of the distribution affects the total estimated time considerably. In addition, the skewness of the distribution also affects the results of estimation meaning that realistic assessment of the parameters of the distributions is important. | Time estimation, probabilistic approaches, tunneling, activity duration, production effort
T04: Deep mining and tunnellingTuo CHEN, Hani S. MITRIMcGill University, CanadaUnplanned ore dilution control in longhole mining using sill pillars – A case study1521 This paper discusses the main causes for unplanned ore dilution in longhole mining and possible mitigation measures. It reports on the results of a case study of an underground mine that uses the longitudinal retreat method for the extraction of a narrow gold-silver orebody. The study is conducted with finite difference software FLAC3D. The modelling technique tracks and fills the cavities created by progressive overbreak with cemented rockfill in bottom-up sequence. In this work, a strategic measure of ore dilution control is explored by incorporating a sill pillar in the mine plan. Comparison of two mine plans - with and without sill pillar - reveals the benefits of sill pillar on unplanned ore dilution control, especially in the three mining levels immediately above the sill pillar. The findings of this work could be equally applicable to similar mining systems with one or more sill pillars in each mine plan. | Underground mining, sill pillar, unplanned ore dilution, numerical modelling
T06: Geological investigation and characterizationGabor SOMODI (1), János BORSODY (2), Ágnes KRUPA (3), Krisztián PETRIK (1), Balázs VÁSÁRHELYI (1)1: Budapest University of Technology and Economics, Hungary; 2: Hidro-Duna Ltd.; 3: Mecsekérc Plc.Rock mass characterization during the construction of a twin-tube motorway tunnel in Hungary1522 A twin-tube motorway tunnel has been under construction near Sopron in Hungary. Geological inhomogeneity during the excavation required the redesigning of the schedule and reorganisation of the project. The geological overbreaks and weak, unstable tunnel faces caused minor stability problems that could be handled locally, but did not substantially affect the planned support. The thick and hard conglomerate layers, harder than expected, caused a significant reduction in the speed of progress and justified the purchase of more powerful excavation tools. A wide tectonic zone appears in the form of several minor dislocations (0.1-1.5 m), characterising a complex strike-slip fault with persistent dislocations caused by minor normal and reverse faulting. This condition represented the most complicated part of both tunnels in terms of stability. Based on the face mapping information, indicator numbers were assigned to the geological layers and then GSI values were calculated using different equations. | weak rock, rock mass classification, calcareous sediment, local instabilities
T07: Geological risks and natural hazardsKatsumi KAMEMURAFukada Geological Institute, JapanSeismic resistance evaluation based on earthquake damage survey data of mountain tunnels1523 Tunnels constructed in the rock formation have been considered safe against earthquakes. However, the 1995 Hyogo-ken Nanbu Earthquake (M7.3) caused large damages to mountain tunnels as many as to other structures. Tunnels are one of the important infrastructures, so the evaluation of seismic resistance is a very important issue. Here damage reports on the 1923 Kanto Earthquake, the 1995 Hyogo-ken Nanbu Earthquake, the 2004 Niigata-ken Chuetsu Earthquake and others in total seven earthquakes are studied and the seismic resistance is evaluated as in the relationship between the seismic intensity and the damage rate. Using this relationship and the earthquake probability provided by official organization, the seismic risk that is very useful tool to plan appropriate earthquake countermeasures can be evaluated. | Mountain tunnel, Seismic damage, Seismic resistance evaluation, Seismic risk
T17: Rock slope engineeringKripamoy SARKAR, Avishek DUTTAIndian Institute of Technology (Indian School of Mines) Dhanbad, Jharkhand, IndiaComparative study of finite and distinct element methods for stability assessment of a jointed rock slope1524 Every year the Himalayan regions of India experience several devastating landslides, which not only claim the lives of people, but also disrupt transportation facilities and the environment in general. The present study deals with assessing the instability conditions of a road-cut slope, under saturated conditions, using kinematic analysis with the help of Dips software, and two numerical simulation techniques, viz., the finite and the distinct element methods using the software packages RS2 and UDEC respectively. Probable mode of failure represented by the distinct element modeling agrees well with that predicted by the kinematic analysis of the slope. The results of the analyses suggest that the distinct element approach is a better suited technique for stability analysis of heavily jointed rock slopes compared to the finite element approach. The studied slope has been found to be unstable, hence few remedial measures have been suggested to improve its strength. | Road-cut slope, Numerical simulation, Finite Element Method, Distinct Element Method, Stability analysis, Himalayas
T07: Geological risks and natural hazardsMaddalena MARCHELLI, Valerio DE BIAGIPolitecnico di Torino, ItalyEvent tree analysis and time-integrated reliability design approach for quantifying rockfall risk reduction1526 The quantification of risk in terms of loss of lives represents the essential parameter to manage rockfall risk in urbanized areas. Rockfall barriers are among the most adopted structural mitigation measures. Despite their wide use, the partial safety factors design approach is not able to guarantee a specific failure probability and, consequently, to assess the precise risk reduction. To tackle all these issues, a quantitative risk assessment method for infrastructures and a time-integrated reliability design approach for rockfall barriers developed by the Authors are combined in a unique framework to quantify risk reduction. The former computes the risk as annual probability of having at least one fatality; the latter allows defining an annual failure probability for a given product in a given site. Merging these methods, the evaluation of risk reduction in case of barrier installation or the definition of the required performances, are defined. An example of application is provided. | Rockfall Risk, Reliability based design, Event tree Analysis, Rockfall barrier
T13: Numerical methods in rock engineeringJian LIU, Long YU, Xingguang ZHAO, Liang CHEN, Ju WANGCAEA Innovation Center for Geological Disposal of High-Level Radioactive Waste, Beijing Research Institute of Uranium Geology, Beijing, ChinaEstimation of fracture diameter probability distribution based on truncated trace-length data1527 Fracture size is a foundational parameter in the evaluation of mechanical and hydraulic properties of rock masses for constructing geological disposal repository. Washburton’s equation and Abel’s integral are widely used in estimating the probability density function of fracture diameter, g(x). However, negative values of g(x) appear in some cases because of the use of Abel’s integral. Besides, the complete curve of trace-length probability density, h(y), is always needed for estimating g(x), while it is almost impossible to get the whole curve of h(y) because of the truncation error. In this paper, a new method of estimating g(x) based on truncated trace-length data was proposed. Instead of using Abel’s integral, g(x) was fitting with a piecewise linear function and thus the problem of negative values of g(x) was also avoided. Case studies with truncated trace-length data indicate that the proposed method is effective in estimating fracture diameter probability distribution. | Fracture Diameter, Trace-Length, Probability Density, Washburton’s Equation
T17: Rock slope engineeringTao XU (1), Zhiguo LI (1), Tianhong YANG (1), Xiaobing ZHENG (1), Wancheng ZHU (1), Tengfei FU (2)1: Northeastern University, People's Republic of China; 2: CSCEC-TAISEI Construction Ltd., Beijing, ChinaSub-critical crack growth based time-dependent deformation model and its application to open-pit slope stability1528 A subcritical crack growth based deformation model was established to describe the time-dependent deformation and fracturing of rock. In conjunction with the uniaxial compression test of rock, the microscopic parameters of the model were calibrated, and the accuracy of the creep model and parameter calibration were verified using uniaxial compressive creep tests. Finally, the established time-dependent deformation model of rock was applied to the time-dependent deformation analysis of a slope in the Fushun West open-pit mine. This study shows that the time-dependent deformation model of rock established in this study can effectively describe the accelerated stage of rock creep, and the simulation results agree well with the experimental results. After the continuous deformation, cracks are formed by the stress concentration at the bottom of the slope under the influence of unfavorable factors, which continuously extend to the top of the slope and form a sliding surface, resulting in unstable sliding. | rock slope, creep deformation, subcritical crack growth, slope stability, numerical simulations
T17: Rock slope engineeringKrishna Kanta PANTHI (1), Chhatra Bahadur BASNET (2)1: Norwegian University of Science and Technology (NTNU), Trondheim, Norway; 2: Clean Energy Consultant Pvt Ltd, Kathmandu, NepalRock cut slope excavated for Settling basins of Seti Khola Hydropower Project1529 Stability of a cut-slope at the headworks area of the hydropower projects is very important for smooth operation of hydropower plant. Underestimation during construction period may bring a catastrophic consequence. This manuscript presents overall assessment results of the rock cut slope excavated to accommodate two settling basins of Seti Khola Hydropower Project (22 MW) located at Lekhnath, Kaski, Nepal. The height of the cut slope is about 50 m and is among the most challenging part of the construction work. The cut slope is excavated in a highly schistose and deformed phyllite with interbedding of metasandstone layers. The evaluations are made on the overall rock mass and discontinuity characteristics. The results of detailed stability assessment using software program SLIDE in consideration with both normal and seismic loading conditions are presented. Final rock support measures are proposed to ascertain long-term stability of the cut-slope. | Settling basin, diversion dam, groundwater, earthquake, stability assessment
T01: Challenging rock engineering projectsWalter WITTKE, Martin WITTKE, Patricia WITTKE-GATTERMANN, Bettina WITTKE-SCHMITTWBI GmbH, Germany50 km of Tunnels in Inner-City Areas – Rock Mechanics and Tunneling Issues in Connection with the large-scale Railway Project Stuttgart 21 – A Success Story1530 For the large scale railway project Stuttgart 21 more than 50 km of tunnels were constructed in the city of Stuttgart. Currently, the tunneling works at the new airport station are carried out, while the other tunnels have already been finalized. In connection with the project, numerous challenges of rock mechanics and tunneling have been solved from the design point of view as well as from the construction point of view. These are – amongst others – 17 km of tunnels in anhydrite, full face excavation of large cross sections with A > 200 m², compensation grouting, TBM tunneling in sedimentary rock, various underpinning measures and the excavation of complicated large shafts and tunnel structures in geologically pre-stressed clay stones of the Jurassic. The paper gives an overview on the project and presents some of the highlights of rock mechanics. | Tunneling, Rock Mechanics, Swelling Rock, Large Cross Sections, Underpinning, AJRM
T06: Geological investigation and characterizationHongkyu YOON, Jennifer HARDINGSandia National Laboratories, United States of AmericaPhysics-informed machine learning of flow and transport problems1531 Recent advances in machine learning/deep learning (ML/DL) methods show promising results to enhance our ability to develop fast surrogate models and estimate heterogeneous subsurface properties through inverse modeling approaches. In this work we explore physics-informed neural networks (PINNs) as a way to incorporate governing partial differential equations (PDEs) in the ML framework through loss functions. With advection-dispersion-reaction (ADR) and Darcy equations, PINN methods are evaluated for multiple cases by changing model parameters and the inverse modeling framework. This work demonstrates that PINNs tend to perform better than data-driven only model with less collocation points and the potential capability of PINNs for accurate surrogate models to coupled geomechanical problems in the subsurface. | Machine learning, Physics-informed neural network, Inverse modeling, Advection-dispersion-reaction
T13: Numerical methods in rock engineeringAhmet Gunes YARDIMCI, Mustafa ERKAYAOGLUMiddle East Technical University, TürkiyeProduction Sequence Analysis of an Overhand Cut-And-Fill Mine in a Narrow-Vein Type Orebody Using Numerical Modeling1532 Excavation-induced stresses have the potential to trigger instabilities around underground openings due to disturbance of the pre-mining stress field. Production sequence is a critical aspect in underground mining as it controls the stress distribution in the rock mass. The cut-and-fill mining method requires consideration of the mining sequence to mitigate the instability risk due to excessive stress concentration in stopes scheduled for production. This study covers the effects of production sequence on the crown pillar and the global mine stability using numerical modeling. A transition from open pit to underground mining in Western Türkiye was investigated. The orebody is a long-narrow vein type steeply dipping metallic mineralization that has three uniformly striking sub-sections. 2D and 3D elastoplastic models were used to examine the crown pillar deformations in alternative production scenarios. Large-scale effects of producing the orebody sub-sections in various orders were studied considering the global mine stability. | Underground mining, production sequence, open pit underground transition, numerical modeling
T07: Geological risks and natural hazardsJoão Paulo MONTICELLI, Rogerio RIBEIROSão Carlos School of Engineering University of São Paulo, São Paulo, BrazilA study case of a rockfall event in a geomorphosite from the Corumbataí Geopark Project, state of São Paulo, Brazil1537 Many geomorphosites are under a natural risk scenario, as those from the Corumbataí Geopark Project, state of São Paulo, Brazil. This paper shows a rock fall event in the Camelo Hill geomorphosite. The area is used by walkers, climbers, mountaineers and civilians in general as a touristic spot in the Geopark domain. In October 2022, a boulder fell from the cliff and destroyed many trees along the slope until stopping at the dirt road used for local tourism. Herein, we have identified the rock detachment source area using field investigations and UAV mapping; an inventory of rockfalls was created and compared to the recent event. Characteristics of the rock travel distance were raised to guide the local authorities. This study also presents a new kind of source area, a rock fall conceptual model for tropical conditions, created to elucidate the mass movement to civilians. | Rock fall, drone, conceptual model, travel distance, geomorphosite, geopark
T15: Rock and rock mass propertiesLichun JIA, Hu DENGDrilling & Production Technology Research Institute, CNPC Chuanqing Drilling Engineering Company Limited, People's Republic of ChinaExperimental evaluation of anisotropic dynamic and static elastic modulus in deep Longmaxi shale1538 Understanding the anisotropic elastic properties of deep Longmaxi shale is crucial for analysis of wellbore stability and hydraulic fracturing in this reservoir. Here, the anisotropic dynamic and static elastic properties are measured under dry, soaked by water-based and oil-based drilling fluid conditions. The results show that the anisotropy parameters ε, γ and δ calculated from wave velocities are less 1 for dry or soaked samples, indicating that this shale is a weak anisotropic rock. And the dynamic Young’s modulus E11 substantially exceeds E33 in all cases and both increases with confining pressure. From compression tests, the static Young’s modulus E0°, E45°, E90° increase with confining pressure but decrease dramatically of soaked samples. In conclusion, the dynamic Young’s moduli exceed static values regardless of direction, confining pressure, dry or soaked condition. And factors affecting the anisotropy of deep shale include the lower amount of clay content and less clumped clay minerals bands. | deep Longmaxi shale, transversely isotropic, ultrasonic wave measurement, uniaxial and triaxial compression tests, dynamic elastic modulus, static elastic modulus
T15: Rock and rock mass propertiesLichun JIA, Qicong XUDrilling & Production Technology Research Institute, CNPC Chuanqing Drilling Engineering Company Limited, People's Republic of ChinaThe tensile strength and failure characteristics of transversely isotropic deep Longmaxi shale under Brazilian test1539 A series of Brazilian tests are conducted to investigate the anisotropic tensile failure of deep Longmaxi shale. The results indicate that the anisotropic Brazilian tensile strength (BTS) of deep shale shows an ascend-slightly decline-ascend trend with loading-bedding angle β. Five tensile failure criteria are used to predict BTS and compared with experimental results, the order of reliability is N-Z criterion > H-B criterion > L-P criterion > SPW criterion > MSPW criterion. Observing from failure of shale specimens, there are four typical fracture patterns: central straight fracture at β=0° and 90°, bedding activation shear failure fracture as β=15°, non-central arc fracture at β=30° and 45°, mixed mode fracture as β=60° and 75°. Moreover, there is an inverse relationship between BTS and bedding activation fracture. The cumulative AE counts-time curve exhibits a stepped increasing mode while AE counts show a monotonic decreasing trend with angle β. | deep Longmaxi shale, transversely isotropic, Brazilian test, Brazilian tensile strength (BTS), failure patterns, AE characteristics
T17: Rock slope engineeringYago Machado Pereira de MATOS (1), Silvrano Adonias DANTAS NETO (2), Guilherme de Alencar BARRETO (2)1: University of Brasilia, Brazil; 2: Federal University of Ceará, BrazilModelling the shear behavior of clean rock joints using Adaptive Neuro-Fuzzy Inference Systems1540 Currently, the development of accurate and reliable models for predicting the behavior of rock mass joints is one of the most common interests among researchers, engineers and geologists. An alternative to address this type of problem more efficiently can be neuro-fuzzy systems, which combine the advantages of Fuzzy Controllers and Artificial Neural Networks (ANN). Therefore, the objective of this paper is to use Adaptive Neuro-Fuzzy Inference Systems (ANFIS) to predict the shear strength and corresponding dilation of unfilled discontinuities of rock masses, incorporating the uncertainties of the variables that govern their shear behavior. It was found that the proposed ANFIS models can be considered a useful tool to predict the shear behavior of clean discontinuities, as they require only some information about the joints characteristics, the intact rock that constitutes their walls, and the boundary conditions imposed on them, without the need for costly and complex laboratory tests. | Clean rock joints, Shear behavior, Neuro-fuzzy, ANFIS, Modelling
T13: Numerical methods in rock engineeringNicholas Ryland BARTONNB&A, NorwayGSI or JRC – continuum or discontinuum modelling – some suggestions and some critique1541 GSI has been applied for about 30 years and JRC for about 50 years. They are associated with either the Hoek-Brown based shear strength criterion for rock masses and continuum modelling, or with the Barton-Bandis based shear strength criterion for rock joints for use in discontinuum modelling. The latter, using input parameters JRC, JCS and φr provides for non-linear and block-size dependent shear-displacement and dilation-displacement behaviour, and non-linear closure-aperture behaviour, including the potential for coupled hydraulic flow modelling. The mismatch of hydraulic and physical apertures is emphasized, requiring lab-scale JRC0 for the conversion. The paper provides some examples of joint-related behaviour in the case of tunnels, caverns and slopes. It also includes serious critique of GSI and the H-B based continuum modelling, due to the complex equations and the lack of representation of joint properties. So-called plastic zones are exaggerated around tunnels, and spoon-shaped slope failures belong in soil mechanics. | modelling, rock masses, rock joints, JRC, GSI, shear strength
T15: Rock and rock mass propertiesSamad NARIMANI GHOURTLAR (1), Seyed Morteza DAVARPANAH (1), László KOVÁCS (2), Balázs VÁSÁÁRHELYI (1)1: Budapest University of Technology and Economics, Hungary; 2: RockStudy Ltd, Pécs, HungaryCharacterization of Poisson’s ratio and Elastic Modulus of granitic rocks: from micro-crack initiation to failure1543 Key geomechanical parameters utilized in rock engineering include Young's modulus and Poisson's ratio. Uniaxial compressive test results are essential in the evaluation of these values. This paper aims to study the process of changes of Poisson’s ratio and Young modulus for intact rock during loading from micro-crack initiation to failure stage. Both Young’s moduli and Poisson’s ratio were calculated using the stress-strain curves. By using parametric investigation, the crack damage stress, determined for Poisson’s ratio-axial stress graphs. Also, this research outline the findings that the variations among the three Young's moduli and Poisson’s ratio estimated for each specimen and suggest the most effective approach for doing so. It was found, that the Poisson’s rate depends on the stress value: it is linearly increasing with increasing stress till the unstable crack propagation stress. Contrary to previous ideas, our results suggest that the Poisson’s ratio is not a constant for rigid rocks. | uniaxial compressive test, Poisson’s ratio, Young's moduli, rock mechanical parameters
T07: Geological risks and natural hazardsAdeline DELONCACenter for Research and Innovation in Mining (CIIM), Geomechanics Research Group, Department of Metallurgical Engineering and Materials, Universidad Técnica Federico Santa María, Santiago, ChilePredicting geomechanical hazard: utopia or reality?1544 Geomechanical hazard can be defined as a combination of the probability occurrence of an event and its intensity. Therefore, predicting a hazard level should give information about how (phenomenology of the failure), when (exact time of failure), and how much (with which intensity in terms of volume and energy) the event will occur. Several methods have been developed over the years to assess some or all these components. However, they do not allow a prediction to be made in terms of the time, location, and magnitude of the event. Indeed, in this assessment process, uncertainties are met at each step. Therefore, the prediction could be reached by answering two questions: can we remove all uncertainty? And if we do not have any uncertainty: are we able to predict the hazard? This paper proposed to discuss the two presented questions by going through various works realized during the author’s academic career. | Geomechanical hazard, uncertainties, risk assessment, prediction
T13: Numerical methods in rock engineeringEdjan BUSTAMANTE (1), Edgar MONTIEL (2), Alexandra OSSA (3)1: Universidad Nacional Autónoma de México, México; 2: Srk, Chile; 3: Insituto de Ingenería UNAM, MéxicoEvaluation of inclined loads in pillars stability1545 In underground mining, rock pillars are frequently utilized to provide support within the deposit. Many of these pillars, either due to their geometry or the stress field acting upon them, experience inclined loads. Hence, this study aims to develop local models to analyze the impact of inclined loads on the stability of rock pillars. The models were created using FLAC3D for various types of pillars, and the Hoek & Brown failure criterion was applied, employing equivalent parameters to simulate medium quality rock. Through these models, the influence of inclined loads on pillars and the width-height ratio were examined. The results indicate that pillars exhibit reduced resistance to inclined loads with a shear component, while the strength increases with an increased width-height ratio. | Pillars, inclined loads, caving & numerical modelling
T13: Numerical methods in rock engineeringErick RÓGENES (1,2), Leandro RASMUSSEN (1), Márcio FARIAS (1), Alessandra GOMES (2)1: University of Brasilia, Brazil; 2: DF+ EngenhariaNovel numerical approach to modeling excavation in hard rocks1549 In this work, a new numerical approach based on the Finite Element Method and an implicit continuum formulation, called Continuum Voronoi Block Model-CVBM, is proposed to represent the fracturing process in hard rocks and also the rupture of underground works with high field stresses. In this model, developed with the RS2 program, the rock mass was simulated by a set of blocks, formed by a Voronoi mosaic, joined at their interfaces by joint elements. Different case studies were represented on a laboratory and field scale. The model proved to be robust on the laboratory scale and described the rock's relevant macro-properties in conventional tests: crack initiation stress, crack damage stress, and peak strength. On a field scale, the model represented the mass deterioration process explicitly, captured the rupture geometry, and the excavations' displacements. Such results show the CVBM's potential for modelling the behavior of underground works with high field stress. | Brittle Failure, FEM Model, Voronoi Tessellation, Hard Rocks
T17: Rock slope engineeringÖmer AYDAN (1), Reşat ULUSAY (2), Jose PAVON (3), Nazli Tunar OZCAN (2)1: University of the Ryukyus, Okinawa, Japan; 2: Hacettepe University, Ankara, Turkey; 3: Jose Pavon & Asociados, Asuncion, ParaguayRock Mechanics Characterization of Columnar Sandstone of Cerro Koi (Paraguay) and Some Slope Stability Issues of the Associated Open Pits1551 Unique columnar jointing in sandstone is observed in Cerro Koi site nearby Asuncion (Paraguay). The authors collected some sandstone columns and carried out on some physico-mechanical experiments on rock pieces for the rock mechanics characterization of this unique columns. The outcomes of experiments carried out rock mechanics characteristics of the columnar sandstone as well as frictional properties of natural column surface together with their base-friction angles are presented. Furthermore, the stability of the open pits is investigated and their short and long-term stability are discussed. | Cerro Koi, columnar jointing, sandstone, open pit, mechanical properties, stability, frictional properties
T10: MonitoringVlastimil KAJZAR, Eva JIRANKOVA, Petr KONICEKInstitute of Geonics, Czech Academy of Sciences, Czech RepublicFirst experience with the newly created monitoring system of dynamics of surface changes occurring during the transition into the post-mining stage1553 The study of the manifestations of mining cannot be done without a technology that allows monitoring the dynamics of surface changes. The Automatic Geodetic Monitoring System was developed to obtain measurement data on surface movements at the CSM coal mine. This system will provide data of sufficient frequency and quality to evaluate the surface deformations caused by deep mining. Long-term monitoring will generate a dataset suitable for developing a method for assessing the consequences of mining after mine closure. The monitoring system consists of two automatic total stations with an integrated 3D laser scanner, GNSS sensors and other accessories. The monitoring period was set to cover, at least in part, the main phase of surface movements caused by underground mining and their subsequent fading in time. However, it is important to note that measured data accuracy can be affected by various adverse factors, prompting ongoing enhancements to the monitoring system. | subsidence, MultiStation, monitoring, hard coal, mining, post-mining
T09: Long term behaviour of underground structuresJintong ZHANG (1), Zhihong ZHAO (1), Junyu CHEN (1), Xingguang ZHAO (2), Ju WANG (2)1: Tsinghua University, Beijing, China; 2: Beijing Research Institute of Uranium Geology, Beijing, ChinaNumerical simulation of nuclide transport at the underground repository scale subjected to thermal loading1554 The nuclide transport with groundwater in the fractured rock is always the primary concern during the long-term operational life of underground repositories. The present paper intends to clarify the effects of thermal loading on in-situ stress, groundwater flow and solute transport at the repository scale. A three-dimensional repository model is built up incorporating a vertical fault and a horizontal fracture. The evolution of temperature, stress, aperture, flow velocity and nuclide transport at different time scales is analyzed and discussed. The thermal disturbance induces a significant distribution of temperature and contributes to the increased stresses in the rock matrix. The fracture and fault dominated convection and hydrodynamic dispersion are disturbed by the reduced aperture and the slow flow velocity around the repository. The nuclide transport is retarded under thermal loading conditions. The higher thermal conductivity in the repository induces to faster thermal decay and ultimately facilitates the nuclide transport. | Nuclear waste repository, Nuclide transport, Thermal loading, Fracture, Thermal conductivity
T01: Challenging rock engineering projectsLineu Azuaga AYRES DA SILVA (1), Guilherme Gianotti de ANDRADE (1), Anna Luiza Marques AYRES DA SILVA (1), Fábio ZATZ (2)1: University of São Paulo, Brazil; 2: Ayres da Silva e AssociadosTheory and practice in the boulders and rock blocks blasting in urban areas applied to civil engineering activities1555 Blocks of rock are large fragments of the bedrock that have not suffered a strong erosive process and have remained in the soil horizons. They can be oval shaped, or nearly spherical. The calculation for blasting is different, as the volume between these blocks varies, and so does the number of holes required. Thus, a calculation method (Ayres da Silva, A. & Gianotti de Andrade, G. Method) was developed for the oval-shaped rock blocks. Finally, in the blasting of blocks using explosives, it is necessary to find what is the block’s volume to be blasted, because this value is fundamental to obtaining a safe amount of explosives needed for a given specific charge. | Boulders, Boulder blast, Rock block blast, Boulder blast design
T08: Hydropower projects and damsMarco QUIRION, Dolice DONTSI MAKENHydro-Quebec, CanadaBehavior of the Rock Foundation of a Concrete Dam Affected by Alkali-Aggregate Reactivity1556 The Beauharnois dam is located near the city of Montreal (Quebec, Canada). The water intake and the powerhouse are founded directly on a quarzitic sandstone rock mass. The coarse aggregate used in the concrete to build the dam originates from these rocks and has a high reactivity to cement alkalis. This reactivity called alkali-aggregate reaction (AAR) is a slow reaction that causes the concrete to swell. Regarding the foundation, swelling of the concrete led to the transfer of stresses to the rock foundation. The intact rock is of high resistance and the rock mass of good quality. The dam foundation is stable to sliding despite the sub-horizontal bedding of the sandstone and the transferred stresses. However, it is shown that, locally, depending on the intensity and orientation of the stresses, they can contribute to the vertical opening of discontinuities near the concrete-rock interface. | Dam, Foundation, Alkali-Aggregate Reaction, Discontinuities, Stresses
T01: Challenging rock engineering projectsLineu Azuaga AYRES DA SILVA (1), Anna Luiza Marques AYRES DA SILVA (1), Guilherme Gianotti de ANDRADE (1), Geronimo Lima RODRIGUES (2)1: University of São Paulo, Brazil; 2: Telar Engenharia e Comércio S.A.Design of controlled rock blasting for tunneling and tunnel portals1557 Today there is a high demand for transport tunnels in Brazil, where the lack of logistical infrastructure is highlighted by the crowding of vehicles on highways and the congestion of trains on existing networks. The solution is overcoming the topographical relief complexities in urban centers and railway networks. This article deals with one of the tools for solving these problems: the fire plan for controlled rock blasting when opening tunnels and their portals, especially when the work of art is built under restricted conditions; geographic location, rock mass structural and mechanical characteristics, stress states arising from depth or induction from previously existing structures, interference with other transport routes, etc. in addition to all aspects inherent to blasting, such as vibration propagation, explosive force, and other parameters to be considered in its application. It should be noted, in this dimensioning, the use, among others, of the Line Drilling technique. | Tunnel, Rock blasting, Line Drilling, Tunnel portal
T10: MonitoringGhader SAADATI (1,2), Michael METT (2), Kontrus HEINER (2), Barbara SCHNEIDER-MUNTAU (1)1: Unit of Geotechnical Engineering, Department of Infrastructure Engineering, University of Innsbruck, Austria; 2: Dibit Messtechnik GmbH, AustriaUsage of Monitoring Data to Optimize and Validate the Geotechnical Parameters of Rock Properties in the Underground Space1558 Determining parameters, including geomechanical characteristics of rocks or rock mass, initial stress state, underground water conditions, permeability, etc., with high accuracy is difficult and expensive due to the complexity of the geological conditions. On the other hand, analyzing the stability of tunnels and determining the behavioral characteristics of the rock mass with numerical methods has limitations in terms of the validity of the input and output data. One of the practical methods to solve these problems is the use of monitoring system in underground space, which aims to measure displacements and can give an estimate of the stability of structures and rock mass. One possible way to validate or determine parameters on site is the use of precision instruments and perform back analysis on the resulting deformation data. In this research, different back analysis methods are investigated to validate rock masses parameters in tunnels. | Monitoring system, Back analyse, Numerical methods, Underground space, Rock mass parameters
T13: Numerical methods in rock engineeringCaitlin FISCHER, Mark DIEDERICHSQueen's Geomechanics and Geohazards Group, Department of Geological Sciences and Geological Engineering, Queen's University, CanadaAnalyzing numerical grouted rockbolt behaviour in jointed pseudo-discontinuum models1561 Pseudo-discontinuum numerical models, where discontinuities such as joints are represented discretely in an otherwise intact rockmass (termed “explicit” models in this paper), can demonstrate spatially variable rockmass response with movement along discrete geological structures. Explicit models used for the design of tendon rock support can therefore produce localized axial and shear loading in rockbolts crossing discrete joints. With strain-based and displacement-based failure criteria becoming increasingly common for predicting the performance of tendon ground support in underground excavations, the interaction between the rockmass and rockbolts must be understood. This paper demonstrates that the selected numerical rockbolt model and rockbolt input parameters govern the interaction between the rockmass and the rockbolt, and the displacements that occur in both systems. | Explicit Numerical Modelling, Jointed Rock, Grouted Rockbolts, Rockbolt Models, Rockbolt Displacement, Strain-based Design
T15: Rock and rock mass propertiesHaiyang ZHANG (1,2), Feiyang LIU (1,2), Jian LIU (1,2), Xingguang ZHAO (1,2), Ju WANG (1,2)1: Beijing Research Institute of Uranium Geology, Beijing, China; 2: CAEA Innovation Center for Geological Disposal of High-Level Radioactive Waste, Beijing, ChinaThermo-hydro-mechanical coupling Triaxial Test Method for Rock with Fracture and Its Application1563 All kinds of fracture discontinuities in granitic host rock of high level radioactive waste (HLW) repository not only degrade the engineering characteristics of rock mass, but also constitute potential groundwater seepage channels and nuclide migration channels. During repository operation, the expansion and evolution law of host rock fractures under the coupling effect of radiation heat, groundwater and stress field is of great significance for the long-term safety assessment of the repository. In this context, a triaxial test method suitable for rock with single fracture under the condition of thermo-hydro-mechanical (THM) coupling is proposed, which solves the problem that the rock sample with fracture as initial defect is easy to be destroyed due to the changes of complex test conditions such as temperature, hydraulic pressure, confining pressure and axial load. | repository host rock, thermo-hydro-mechanical coupling, triaxial test, crack propagation
T10: MonitoringMiguel PAGANIN NETO, Elder Lucas RIBEIRO, Christiano NOGUEIRA, João Pedro DELVEAUX, Wesley de Lima SILVA, Camilla Szerman EUZEBIOVALE S.A.Optimization of a large-scale slope monitoring system by the correlation between interferometric radar and geological compartmentalization1566 The implementation of a monitoring system able to catch geotechnical events in large-scale open pits is challenging and requires a combination of different technologies, since rock masses are heterogeneous. Traditional monitoring systems commonly treat rock masses as a discrete and homogeneous domain, which is not representative of the global slope failure process with differentiated deformation along the structure, due to different rock types, joint families and rheology. Interferometric radars have been used as a potential tool in monitoring large-scale geotechnical failures, since they could give a rapid response in all scale deformation, characterize the behavior of the movement, and predict failure time using tools, as inverse velocity. Regardless of the scale of slope monitored, the data obtained is rarely associated with rock types and rheology. This article presents an optimization of a large-scale slope monitoring system, correlating interferometric radar and geological compartmentalization, in a real case of global slope failure. | monitoring system, terrestrial radar, global slope failure, rock mass, sectorization
T10: MonitoringAlbert GREINMEISTER (1), Johann GOLSER (2), Alexander RADINGER (2), Gernot JEDLITSCHKA (3), Manfred EDER (4), Micheal FELDINGER (5), Franz RATHMAIR (6), Erich SAURER (7)1: Salzburger Regionalstadtbahn Projektgesellschaft mbh, Salzburg, Austria; 2: Geodata Surveying and Monitoring Group, Leoben, Austria; 3: JV TSS – Team Schiene Salzburg, Puch, Austria (Geoconsult ZT GmbH); 4: JV TSS – Team Schiene Salzburg, Puch, Austria (Laabmayr ZT GmbH); 5: JV TSS – Team Schiene Salzburg, Puch, Austria (IGT Geotechnik und Tunnelbau ZT GmbH); 6: Keller Grundbau GmbH, Linz, Austria; 7: Skava consulting ZT-GmbH, Salzburg, AustriaMonitoring and analysis of the behavior of the Salzburg-Clay during the jet grouting works for the S-LINK project1567 The underground railway line project S-LINK aims for a fast rail connection within the Greater Salzburg Area. The alignment in the first section, starting from Salzburg main station southwards runs underground. The subsoil along the alignment consists of a few meters of fill and gravel in the uppermost section, followed by fine sand-dominated and silt-dominated lacustrine deposits with varying clay and a high water content, which are locally referred to as "Salzburger Seeton". In order to increase the robustness and reliability of the design and optimize the relevant construction parameters, the jet grouting method and its effect on adjacent soil and structures were tested in a test field. The main purpose of these tests was knowledge acquisition for the best possible application of the method under the given geological conditions as basis for design. In this article, the relevant boundary conditions, objectives and results of the test field are presented. | Monitoring, Data Acquisition, Jet Grouting
T15: Rock and rock mass propertiesSujeet BHARTI (1), Rakesh KUMAR (1), Debasis DEB (1), K. U. M. RAO (1,2)1: Indian Institute of Technology Kharagpur, India; 2: National Institute of Technology Rourkela, IndiaA Mathematical Model for Shear Stiffness and Dilation for Saw-Tooth Joints under CNL Conditions1569 An extensive direct shear test program has been conducted on regular saw-tooth artificial joint samples under constant normal load (CNL) conditions. The analysis of shear data reveals that shear stiffness (k_ss=dτ⁄du) and dilation (ψ=dv⁄du), where τ and v are the shear stress and vertical displacement respectively, are not constants throughout the evolution of shear stress. Rather, it is clear that both the variables change non-linearly with shear displacements (u) and can be approximated by two-parameter hyperbolic function with respect to u. These parameters are estimated using regression analysis using the experimental data. From the functions k_ss (u) and ψ(u), a shear displacement exists at which the basic friction angle occurs. Also, it is found that this displacement occurs where contraction ends and dilation begins. Based on that, the dilatant behavior and evolution of peak shear strength can be described leading up to the determination of dilation angle at the peak stress. | saw-tooth joint, direct shear test, mathematical model, shear stiffness, dilation
T15: Rock and rock mass propertiesWalter STEINER (1), Fritz MADSEN (2), Jean-François MATHIER (3)1: B+S AG, Bern, Switzerland; 2: Consultant, ret. ETHZ. Adliswil, Switzerland; 3: Consultant, ret. EPFL, Avenches, SwitzerlandSwelling pressures of clay rocks from laboratory tests: experience and improvements1575 Swelling in underground works can cause severe problems during and after construction. Consequently, swelling potential must be identified and quantified prior to construction. ISRM recommendations exist but not all interpretations are included and not all applied testing procedures follow these recommendations. Swelling pressures are not only influenced by the testing procedure, but also by the sampling technique and the conservation, transportation, and protection procedure of the samples, as well as the lab equipment. The construction of the test apparatus and the testing procedure both influence the test results. Swelling pressures can be determined by confined swelling tests. However, for incremental loading and unloading tests, often called Huder-Amberg tests, the procedure to determine swelling pressures are not well defined and the authors noted large deviations to the results of swelling pressure tests. A different technique to determine the swelling pressure from the incremental test is presented. | swelling, clay rocks, shale, laboratory tests, tunnels, heave
T04: Deep mining and tunnellingTobias LADINIG (1,2), Patrick GAMS (1), Horst WAGNER (1), Matthias WIMMER (2), Michal GRYNIENKO (2)1: Chair of Mining Engineering and Mineral Economics, Montanuniversität Leoben, Austria; 2: Rock Engineering Kiruna Mine, LKAB, SwedenAddressing rock engineering challenges faced in the development of a novel, deep mining method1576 Raise Caving is a novel mass mining method utilizing an active stress control approach for the foresighted, strategic and systematic control of rock pressure. The active stress control approach is based on a slot-pillar system, which is established prior to large-scale mineral extraction. From a rock engineering point the challenge is to design initially strong pillars, which are required to provide and maintain a favorable stress environment for establishing the de-stress slots. As large-scale mineral extraction commences, the pillars have to be weakened stepwise to create a regional de-stressed area for mineral extraction. The critical issue is to manage this process such that pillar strength degradation takes place in a stable controlled manner. The paper discusses rock engineering considerations related to pillars. The investigations show that the design of pillars and the regional extraction sequence are crucial and that design criteria for infrastructure and mining-induced seismicity need to be developed. | Deep mining, Rock Mechanics, Cave Mining, Raise Caving, Stress Control, Pillars
T15: Rock and rock mass propertiesMengsu HU (1), Laura PYRAK-NOLTE (2)1: Lawrence Berkeley National Laboratory, USA; 2: Purdue University, USAThe Interplay between Geometry and THMC Processes1577 Earth systems consist of materials with complex geometric features undergoing complex coupled thermal-hydro-mechanical-chemical (THMC) processes. These geometric features when combined with THMC processes govern the formation and transformation of rocks and thus understanding this coupling is essential for rock engineering activities. In this paper, we aim to address the following scientific questions by presenting a series of examples from numerical modeling and laboratory experiments: (1) How does fracture asperity geometry affect compaction and shearing that control single-fracture mechanical and flow properties? (2) How do intersections of fractures affect deformation, fluid flow and chemical reaction? (3) What controls key processes such as pressure solution during the formation of sedimentary rocks? Through these examples, we will show that it is important to properly address the complex geometry and coupled processes to understand evolving Earth systems to maximize their potential use for energy recovery and storage. | Geometry, THMC, Fractures, Interfaces, Pressure Solution, Earth Systems
T04: Deep mining and tunnellingZulfiqar ALI (1), Murat KARAKUS (1), Giang D. NGUYEN (1), Khalid AMROUCH (1,2), Chris CHESTER (3)1: The University Of Adelaide,Adelaide, Australia; 2: Mohammed VI Polytechnic University, Benguerir, Morocco; 3: OZ Minerals, Adelaide Airport, SA 5950, AustraliaIn-situ stress measurement using non-destructive and relief methods1578 Over the past many decades, in-situ stress measurement using overcoring (OC) and hydraulic fracturing (HF) methods has been scientifically accepted and commercially adopted worldwide. However, with the mines getting deeper, their application has become more cumbersome and costlier. This paper presents the use of non-destructive techniques like the secant modulus method (SMM) and acoustic emission (AE) for in-situ stress measurement. Cyclic tests were performed on sub-cores extracted in six independent directions from the oriented main core having a trend and plunge of 285o and 75o respectively in the mine grid. The cores were retrieved from a mine site in South Australia where the OC method was applied. A minimum of two sub-cores were tested in each direction to get the complete stress tensor. The deformation was monitored using strain gauges and AE monitoring system. Results show a very good estimate of in-situ stresses that compares well with the OC method. | Kaiser Effect; Stress Memory; Secant Modulus Method (SMM); Acoustic Emission (AE); Overcoring (OC)
T13: Numerical methods in rock engineeringXu ZHU, Min GAO, Guangyao SI, Chengguo ZHANG, Joung OHUniversity of New South Wales, AustraliaModelling the hydro-mechanical behaviour of a 3D rough-walled rock joint1580 The geometrical morphology of single rock joints considerably impacts the hydromechanical behaviour of fractured rock mass. Although the influences of various geometrical parameters on flow behaviour have been well-studied, only a few previous studies explored the interactions of shear-flow processes in evaluating flow behaviour through a rock fracture. This paper presents numerical simulations for coupled shear-flow processes in single rock fractures based on an improved hydro-mechanical model. The model considers the evolution of the contact area ratio based on Grasselli’s criterion as well as the variable aperture distributions during shearing, and the associated effects on the flow behaviour. The proposed model is then numerically incorporated into the discrete element code 3DEC to conduct shear-flow test simulations, thereby demonstrating the performance of the model. A number of shear-flow tests are performed on single rock fractures. The simulation results are verified by comparison with experimental results, and an acceptable agreement is achieved. | Rock joint, Numerical simulation, Contact area, Aperture distribution, Shear-flow coupled
T07: Geological risks and natural hazardsZheng GONG (1), Jang-guen LEE (1), Gyu-Hyun GO (2)1: Future Smart Construction Research Division, Korea Institute of Civil Engineering and Building Technology, Republic of Korea (South Korea); 2: Department of Civil Engineering, Kumoh National Institute of TechReview and evaluation of Porosity Rate Model (PRM) for highly frost susceptible soils1581 Frost heave is a frost action when the soil temperature is below freezing temperature. Construction in cold regions is difficult and might cause serious damage to structures. Therefore, it is important to estimate frost heave before construction. The purpose of this study is to introduce and modify a model that can predict frost heave behavior through the change in soil porosity. The Porosity Rate Model (PRM) is possibly applicable for engineering purposes in describing the frost heave process, but the previous studies only focus on clayey soils which may not be frost susceptible soils. This paper presents an assessment of PRM on frost susceptible soils prepared by sand-silt mixtures. Comparisons were made by comparing the predictions obtained with the same initial conditions on the PRM using frost heave data for frost-susceptible soils. Results show good agreement between them, PRM was found to be equally applicable to frost-susceptible soils. | Frost Heave, Porosity Rate Model, Frost Susceptible, Silt
T10: MonitoringMuammer BERBEREldorado Gold (TUPRAG Efemcukuru Gold Mine), TurkeyGeotechnical Risk Assessment and Management with Underground Controls and Monitoring System for Sill Pillar Recovery at Tüprag Efemcukuru Gold Mine1583 Geotechnical assessment was used to define the mining method, the production schedule, and potential risks for the recovery of sill pillar left at two levels, namely 555 Level and 595 Level. According to geotechnical assessment production was planned for the pillar by using transverse blind up-hole stopes, which are accessed via drift driven in orebody, on the hanging wall side where was planned to monitor the ground movement with smart cable bolt. Consequently, records and cracks along hanging wall, potential risk was detailed with re-assessment that involved the elastic deformation of the paste fill measured in UCS tests were used to anticipate the regional displacement. Also, another instrument named smart MPBX’s were used for modelling accurate movement. All results of monitoring have been recorded and correlated with mining activities. In conclusion, a new access drift on the footwall has been designed and the production sequence and schedule has been updated. | Smart, Cable, MPBX, Monitoring, Assessment, Geotechnical
T05: Digitalization & AutomatisationJinfan CHEN (1), Zhihong ZHAO (1), Xingguang ZHAO (2)1: Tsinghua University, Beijing, China; 2: Beijing Research Institute of Uranium Geology, Beijing, ChinaDeep learning-aided prediction of peak shear strength of rock fractures1585 A robust estimation of peak shear strength of rock fractures in engineering practice is significant, but the three-dimensional (3D) surface characteristics of fractures have not been comprehensively quantified in the existing models. In this study, a deep learning-aided prediction method is proposed to estimate peak shear strength of rock fractures by considering the 3D surface roughness characteristics. The dataset is generated by numerical simulations after experimentally calibrated, and contains four features (normal stress, rock mechanical properties, relative fracture elevation). The deep learning model (FracSNet) assisted by data augmentation and fine-tuning is developed to provide reliable peak shear strength prediction of artificially-split fractures. The prediction ability is validated utilizing experimental data, and the results demonstrate that FracSNet can provide reliable prediction. The deep learning model of rock fractures has great a potential in engineering application with limited access to experimental data. | Peak shear strength, Rock fractures, Particle-based discrete element method, Deep learning
T04: Deep mining and tunnellingTao LIN (1), Zhihong ZHAO (1), Wen MENG (2), Xingguang ZHAO (3)1: Department of Civil Engineering, Tsinghua University, Beijing, China; 2: Key Laboratory of Neotectonic Movement and Geohazard, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, China; 3: CNNC Key Laboratory on Geological Disposal of High-level Radioactive Waste, Beijing Research Institute of Uranium Geology, Beijing, ChinaCoupled thermal and unloading-induced permeability of rock fractures1586 The behavior of fluid flow through rock fractures is a critical issue in many subsurface rock engineering projects. Previous studies focused more on the permeability evolution of rock fractures under loading stage, while the change of fracture permeability under unloading stage is more consistent with the actual engineering excavation. To examine the unloading-induced changes in fracture permeability under different temperatures, we performed flow through tests on fractured core samples subjected to decreasing confining pressures and constant temperatures. The results show that the permeabilities of fractures under unloading confining pressure increase but decrease with increasing temperature because of fracture closure caused by asperity damage and thermal expansion. A coupled thermal-mechanical model considering asperity damage is used to explain the unloading-induced changes in fracture permeability. The coupled thermal-mechanical model properly predicts the experimental results. | Unloading, Permeability, Rock fracture, Temperature
T12: New developments in rock supportKunze LI, Hamed LAMEI RAMANDI, Chengguo ZHANG, Sahand TADBIRI, Serkan SAYDAM, Joung OHUniversity of New South Wales, Sydney, AustraliaInfluence of rock crystal structure on bond strength at the rock-shotcrete interface1587 The bond strength at the aggregate-cement paste interface is affected by the microstructure of the interfacial transition zone (ITZ). However, the influence of substrate crystal structure on the rock-shotcrete interface behaviour has received limited attention. This study investigates the impact of substrate crystal structure on the bonding strength of the rock-shotcrete interface. Gabbros and basalts used in this study have similar mineral compositions but have different grain sizes due to different cooling rates. Applying plain shotcrete to substrate samples to study the interface behaviours. Direct pull-off tests are conducted to investigate the bond strength at the interface after 28-day curing. The failed surfaces are examined using scanning electron microscopy imaging technique to further analyse the failure interface. The results indicate that hydration products can cover and embed into the rock surface. Basalt with fine-grained texture achieves denser ITZ than coarse-grained gabbro and results in stronger bond between rock and shotcrete. | Basalt, Gabbro, Rock-shotcrete interface, Bond strength, Crystal structure
T14: Petroleum engineering and carbon sequestrationAly ABDELAZIZ, Phyllis S. WU, Mei LI, Earl MAGSIPOC, Karl PETERSON, Giovanni GRASSELLIDepartment of Civil and Mineral Engineering, University of Toronto, CanadaUnderstanding shale fracture network complexity in the laboratory1588 Hydraulic fracturing is a complex multi-physics process that involves coupling of fluid flow and rock deformation/fracturing. Particularly, the propagation of fluid-driven fractures is a competing process greatly influenced by rock fabric and in-situ stress. However, it remains unclear how rock fabric affects the failure mechanisms and contributes to the resulting fracture network. To understand this, an 80 mm Montney shale outcrop cube was hydraulically fractured in the laboratory under in-situ true triaxial stress conditions. The fractured sample was then digitally 3D reconstructed by merging high-resolution, high-contrast serial section images. In-depth observation of the digitally-reconstructed induced fracture-network revealed the formation of bedding-controlled horizontal fractures, opening against σ2 instead of the theoretically expected σ3. This suggests the key role played by the bedding planes in determining the trajectory of the fluid-driven fracture network. En-echelon fractures observed near the injection borehole are convincing evidence of possible shear failures associated with hydraulic fracturing. | hydraulic fracturing, 3D imaging, serial section reconstruction, true triaxial testing, breakdown pressure, shut-in pressure
T05: Digitalization & AutomatisationChuyen Ngoc PHAM (1,2), Li ZHUANG (1,2), Sun YEOM (1), Hyu-Soung SHIN (1,2)1: Dept. of Geo-Space Engineering, University of Science and Technology, Republic of Korea (South Korea); 2: Korea Institute of Civil Engineering and Building Technology, Republic of Korea (South Korea)Deep Learning based Automatic Fracture Identification in CT Images of Rock1589 Computed tomography (CT) scans have been widely used to study the internal structure of rock including fractures. However, accurately quantifying fractures based on CT data could be challenging due to blurry appearance of fractures in CT images, complexity of fracture patterns and heterogeneity of the host rock. In this study, deep learning-based method is presented for automatically and accurately segmenting fractures in CT images of rock. The method involves two steps: fracture detection using the Faster R-CNN algorithm and fracture segmentation using the U-Net algorithm. The detection step establishes spatial constraints for the segmentation process, significantly removing noise and artifacts in background and improving the final segmentation result. CT images of fractured granite, sandstone and shale were applied for verifying the proposed method. It was found that our method can achieve a Dice score of up to 0.93, outperforming other deep learning approaches including Mask R-CNN or U-Net alone. | Rock fracture, Computed tomography, Deep learning, Rotated bounding box
T15: Rock and rock mass propertiesChongyuan ZHANG (1), Hongtao LIU (1), Ping ZENG (2), Yang XIA (2), Liang WEN (1), Bo ZHOU (1), Bao ZHOU (1)1: PetroChina Tarim Oilfield Company, Korla, China; 2: China University of Petroleum, Beijing, ChinaA statistical damage constitutive model based on residual strength and Drucker-Prager criterion1590 The HTHP (high temperature and high confining-pressure) triaxial compression test has been conducted on dolomite at 8000m deep in the Tarim Basin, China. We first study the characteristics of rock deformation based on the experimental results. An improved damage constitutive model is introduced to overcome the limitations inherent in the existing models which cannot accurately characterize rock residual strength after failure. The Drucker-Prager model serves the failure criterion of the ultradeep rock. The model is used to fit the experimental data and the results show a good agreement, which indicates that the improved model can be used to predict the mechanical behavior during the whole loading process. The model provides a theoretical knowledge of the mechanical characteristics of ultra-deep rocks in Tarim oil field. | Constitutive Model, Residual Strength, Drucker-Prager Criterion, High Confining-pressure, Statistical Damage
T03: Deep geothermal energyChuangchuang WANG, Xueyu PANG, Guodong CHENG, Jiankun QIN, Huajie LIUChina University of Petroleum(East China), People's Republic of ChinaDesign of CaO-Al2O3-SiO2-H2O hydrothermal synthesis systems for high temperature and high pressure applications1592 Hydrothermal synthesis (HS) system is known to have better high temperature resistance than conventional Portland cement-based system. However, there are still many problems with its field application, as thickening time, rheology, and sedimentation stability of HS systems are difficult to tune. In this study, the design of the HS system was optimized in three stages. In the first stage, experiments were conducted to verify the high temperature resistance of the HS system and study the reactivity of different components. In the second stage, experiments were conducted to optimize the engineering performance of the HS system. In the third stage, experiments were conducted to analyze the influence of material ratio, retarder type and alumina on the performance of the HS system. Test results revealed that the AMPS retarder had better performance than tartaric acid at high temperature and all systems had extremely stable physical and mechanical properties. | Hydrothermal synthesis system, Retarders, Field application, Mechanical properties
T17: Rock slope engineeringMuhammad JUNAID (1), Rini Asnida ABDULLAH (2), Radzuan SA'ARI (2)1: National University of Science and Technology; 2: Universiti Teknologi malaysiaEvaluation of Rock Mass Quality using Unmanned Aerial Vehicle Survey for Slope instability Assessment1593 Rock mass quality (RQD) is the fundamental way of evaluation of rock mass quality in mining and geotechnical investigation. However, the estimation of RQD in morphological complex areas is difficult to obtain. In this research work, an unmanned aerial vehicle (UAV) survey was adopted to estimate the RQD at various locations along the slope using volumetric joint counts (Jv). At the centre of the slope, 72% of the data points represent fair rock, while 28% shows poor rock. In contrast, the 20 data point obtained towards the west included 90% of data points for fair rock while 10 % for good rock. Thus, based on his study it is concluded that UAV survey is an efficient way of characterization of rock mass quality. | Slope stability, UAV, RQD, characterization, rock mass evaluation
T13: Numerical methods in rock engineeringKallol SAHA, Resmi SEBASTIANDepartment of Civil Engineering, Indian Institute of Technology, Ropar, IndiaShear wave propagation across jointed rocks of varying seismic impedance1594 Shear waves are considered as one of the damaging waves for any structure built in the rocks during earthquakes, mining, blasting etc. This paper describes the numerical simulation of a test facility that generates shear waves in rocks. The test facility comprises of a dynamic impact mechanism, friction bar, incident, and transmitted plates. When the friction bar is given dynamic impact, shear wave gets generated in the perpendicular direction in the incident plate due to friction present in the interface between friction bar and incident plate. Seismic impedance of the media plays an important role during wave propagation across the interface. The effect of change in material density across the frictional joints was monitored during laboratory testing. These tests were numerically simulated using a distinct element code. Validation of these numerical simulations have been done by monitoring the vibration amplitudes developed at various locations of the plates in the laboratory. | Shear wave propagation, frictional jointed rocks, seismic impedance, energy coefficients, Coulomb slip joint model, continuously yielding joint model
T13: Numerical methods in rock engineeringDima SHAMSEDINE (1), Pooya HAMDI (1), Florian AMANN (1,2)1: RWTH Aachen University, Department of Engineering Geology and Hydrogeology, Aachen, Germany; 2: Fraunhofer Research Institution for Energy Infrastructure and Geothermal Systems, IEG, Aachen, GermanyNumerical Calibration of Laboratory Results of 3D Printed Sandstone Analogues using Finite/Discrete Element Method (FDEM)1595 The study presents the first step of a research project that aims at investigating and modeling the geomechanical characteristics and failure mechanism of rock mass containing non-persistent rock joints using laboratory tests carried out on 3D printed sandstones. This paper focuses on modeling the behavior of intact sandstone analogues under compression and indirect tension tests using a 2D hybrid finite-discrete element method (FDEM) implemented in Irazu software. The advantage of FDEM approach is its ability to model the transition from continuum to discontinuum domain during intact rock fracturing. The models were calibrated against data sets of uniaxial/triaxial compression and Brazilian tests. Stress-Strain curves and failure mechanisms of models were compared to the experimental results, it was shown that the calibrated models could capture the strength and the brittle failure aspect of the sandstone analogues through crack initiation, propagation, and coalescence and are in good agreement with the laboratory results. | FDEM, FEM-DEM, Calibration, Numerical Modelling, Uniaxial Compressive Strength (UCS), Triaxial Compressive Strength (TRX), Brazilian Test
T04: Deep mining and tunnellingLorenzo MILAN, Monica BARBERO, Mauro BORRI-BRUNETTOPolitecnico di Torino, ItalyApplication of a new brittleness index to estimate the proneness to brittle failure of rock around a deep tunnel1596 A major problem that may arise during the excavation of deep tunnels is the incidence of brittle failure of rock, induced by the stress release in a particularly heavy natural state of stress. The severe energy release is often associated to rapid fracturing and to projection of rock blocks inside the opening, phenomena commonly referred to as spalling or rockburst, which endanger personnel and equipment. Thus, the proper prediction of the occurrence of brittle failure is paramount in underground excavations. This paper presents the application of a new rock brittleness index based on the response of two mechanical models of rock damage, which allows the estimation of the proneness to brittle failure of rock around deep tunnels. For this purpose, the competition between ductile and brittle failure is analyzed. The calculation and usage of the index is described considering a real case study of brittle failure in a deep tunnel. | Brittleness index, Rockburst, Spalling, Tunneling
T10: MonitoringBartolomeo VIGNA, Adriano FIORUCCI, Federico VAGNON, Marco BARALEPolitecnico di Torino, ItalySinkholes and underground mining activities: the key role of monitoring for the hazard assessment and mitigation1598 In 2005, the exploitation activities in the Moncalvo underground gypsum quarry in the Monferrato area (Moncalvo, Piedmont Region, NW Italy), intercepted a karst cave filled with pressurized water (0.3 MPa). After this event, a hydrodynamic and hydrogeochemical methodology was developed and coupled to direct observations to monitor the water flows into the quarry. In particular, all the existing water flows and the new ones generated by the mining activities were mapped. Redox potential, electrical conductivity and water temperature were recurrently measured and integrated with chemical analyses. Piezometric levels were also measured in many piezometers located around the quarry site. The proposed methodology was successfully applied to the Calliano gypsum quarry, which is located in the same geological framework but it is representative of a different karst system. The paper highlights the key role of the hydrogeochemical monitoring as a potential technique for the sinkhole risk related to mining activities. | sinkholes, gypsum, hydrogeochemical monitoring, karst hydrogeology
T06: Geological investigation and characterizationÅsa FRANSSONDepartment of Earth Sciences, University of Gothenburg, SwedenHydrogeology and grouting - a field experiment in shallow, crystalline rock1599 When constructing a tunnel or a shaft in a fractured rock mass, the main water-bearing features are of major importance. A limited reduction in leakage, as well as a greater impact area, are potential consequences if these features are not considered in hydrogeological descriptions and in grouting design. This paper presents a grouting field experiment performed in a shallow, crystalline rock mass. An experiment where the spatial distribution of hydraulic conductivity (transmissivity) of water-bearing features was expected to show both directional dependence and connectivity. This was confirmed, grouting was performed, and hydraulic conductivity reduced. We expect that the demonstrated experimental work, highlighting general nature, pattern, and properties, can be used to improve hydrogeological descriptions and grouting design and form a basis for environmental impact assessments. Further, storage coefficient, and hydraulic aperture, based on transmissivity, can, potentially, be an additional indicator of fracture stiffness and situation of stress. | Hydrogeology, grouting, environmental impact, transmissivity, storage coefficient, fracture stiffness
T15: Rock and rock mass propertiesManuel A GONZÁLEZ-FERNÁNDEZ (1), Ignacio PÉREZ-REY (1), Leandro R ALEJANO (1), José MURALHA (2), Seungki HONG (3), Ki-Bok MIN (3)1: Department of Natural Resources & Environmental Engineering, University of Vigo, Spain; 2: Concrete Dams Department, National Laboratory for Civil Engineering (LNEC), Lisbon, Portugal,; 3: Department of Energy Systems Engineering and Research Institute of Energy and Resources, Seoul National University, Seoul, Republic of KoreaDetermining the transversely isotropic elastic constants from strain data by means of different mathematical approaches1601 Mechanical properties of rocks with marked weak planes such as foliation, schistosity or bedding, are not isotropic. The deformability of these rocks is transversely anisotropic (TI), and, therefore, different axial strains are observed according to the load direction, being equal in directions within the weakness plane. Their elastic behavior is theoretically defined by five independent constants. In this study, a relatively large number of strain data sets collected from compressive tests on slate are used to estimate these constants. Two main approaches are followed. The first consists in solving the corresponding compliance matrix equation by means of the least square best fit multi-regression approach in groups of samples, which are then averaged. The second is based on minimizing the error in the stress invariant by means of a non-linear gradient algorithm. Results are analyzed aiming to learn how to manage strain variability in the process of TI elastic parameter estimate. | Transversely isotropic elasticity, Elastic constants, Slate, GRG algorithm
T06: Geological investigation and characterizationDaniel PRADO AZEVEDO (1), Eduardo Antonio GOMES MARQUES (2)1: Universidade Federal do Pará, Brazil; 2: Universidade Federal de Viçosa, BrazilThe use of 3D digital implicit geological models on slope stability evaluation1604 This study highlights the importance of efficient and agile methods in geological-geotechnical evaluations for open pit mining. The use of 3D geological modeling technologies allows for a better understanding of lithological contacts and strength parameters, enabling the assessment of rock mass geometry and slope stability analyses. Implicit modeling software facilitates the creation of detailed geological-geotechnical models, which can be updated with new data. These models provide cross-sections for slope analysis and can simulate future mining progress and water level fluctuations. By utilizing these tools, the quality of evaluations improves, and areas requiring additional information are identified. The paper presents the results of an implicit geological-geotechnical model for an open pit mine and showcases a slope stability analysis conducted on a geological-geotechnical cross-section. Overall, these techniques enhance understanding, improve analyses, and contribute to more reliable open pit mine design. | Slope Stability, Stability Analysis, Softwares, Geotechnics, Implicit Model
T12: New developments in rock supportAna Carolina BAÊSSO (1), Euripedes do Amaral VARGAS JR. (1), Raquel Quadros VELLOSO (1), Eduardo Gomes MARQUES (2)1: Pontifical Catholic University of Rio de Janeiro, Brazil; 2: Federal University of ViçosaDetermination of tensile strength of rocks by CTC (compression-tensile load converter test)1607 In order to obtain the direct tensile strength of the rocks by means of a device that is inexpensive and easy to use in a rock mechanics laboratory, a compression load converter was designed and manufactured in the PUC-Rio laboratory. This apparatus was named as a compression-tensile load converter (CTC), and was developed by Klanphumusri (2010). The equipment design allows the user to switch between tensile stress and compression applications on the same specimen during placement in the conventional compression machine. The apparatus was designed to test dog bone or halter rock samples with end diameter ranging from 75 to 100 mm. Seven specimens of syenogranites from Cachoeiro de Itapemirim, ES - Brazil were tested for equipment validation and the results were compared to those obtained in fifteen Brazilian tests. The direct tensile strength using the CTC showed consistent results, with lower strength than those obtained by the indirect method. | Direct tensile test; Tensile strength of rocks; Load converter, Geomechanical Properties
T06: Geological investigation and characterizationAbhiram Kumar VERMA, Binay Kumar SAWIndian Institute of Technology Kharagpur, IndiaShear strength characterization of a natural rock joint developed in Peridotite deposits1610 The shear behavior of open rock joints in Peridotite rock, igneous in nature, is studied. These joints are open, random, with the most frequent aperture of 1-2 mm, filled with serpentinite, magnesite, chlorite, asbestos, and talk. Roughness are characterized as rough, smooth, undulating, planar, stepped, stepped/smooth plane, rough stepped, stepped undulating, polished, planer rough, and others. Direct shear test at three constant normal load are carried out, and joint characteristic curves are developed to determine their mechanical properties. All joint sample was collected from different boreholes of 75 mm diameter from depth ranging from 13.18 m to 555.78 m. Further, joints basic friction angle, JRC, JCS are determined. Based on these test results, the dilation and peak shear displacement models are developed and compared with existing shear strength models. | Open rock joint, CNL, Direct shear test, Dilation
T13: Numerical methods in rock engineeringJun-Beom AN, Jeonguk BANG, Joo-Hyun SEONG, Gye-Chun CHOKorea Advanced Institute of Science and Technology, Daejeon, Republic of KoreaNumerical evaluation of surface settlement induced by shield tunneling at rock mass1611 There are several precedents of unintended surface settlements resulting in enormous loss of costs and time, even if for the rock medium. The expansion of shield tunneling requires controlling the shield tunneling parameters precisely to reduce the surface settlements. In this study, numerical parametric studies are conducted to evaluate the geotechnical properties, and TBM operational factors on the surface settlements during shield tunneling. The numerical model based on FLAC3D is validated by comparing the results with the literature and field data. Ground stiffness is the dominant factor in the settlement, and the groundwater inflow follows it. The face pressure and tail void grouting pressure show a relatively weak impact on surface settlements because of the higher stiffness of rock mass. The results from this study are expected to contribute to understanding the settlement behavior induced by shield tunneling through the rock mass and the prediction of surface settlement. | shield tunneling, surface settlement, groundwater inflow, face pressure, tail void grouting
T07: Geological risks and natural hazardsReinhard GERSTNER (1), Christine FEY (1), Klaus VOIT (1), Erik KUSCHEL (1), Gerald VALENTIN (2), Christian ZANGERL (1)1: Institute of Applied Geology, University of Natural Resources and Life Sciences, Vienna (BOKU), Austria; 2: Landesgeologischer Dienst, Land Salzburg, AustriaKinematic Analysis and Distinct Element Modelling of a polyphase Rock Fall1612 Rock falls are one of the most hazardous mountain processes and can show variable failure mechanisms. Therefore, a kinematic analysis is commonly performed to assess which failure mechanisms are favoured by the structural inventory of a rock mass. However, often multiple failure mechanisms are thereby considered possible. In our paper, we emphasize this ambiguity and investigate factors controlling the actual rock fall failure mechanism. For this purpose, we have selected a case study in southern Salzburg (Austria), where three rock falls occurred from a highly schistose, metamorphic rock mass in the year of 2019. In our study, we characterized the structural inventory of the rock mass hosting the rock falls and identified possible failure mechanisms by a kinematic analysis. Through distinct element modelling, we show that depending on the persistence of pre-existing structures, the reproduced failure mechanism alternates between the kinematically proposed mechanisms, i.e. block toppling and sliding. | rock fall, initial failure mechanism, kinematic analysis, structural control, distinct element modelling
T04: Deep mining and tunnellingRicardo Isidro FERREIRA, Pinkie NDABA, Richard MASETHESibanye-Stillwater, South AfricaThe implementation of ‘automatic’ polygons for relevant data selection in short-term seismic analysis1613 Mining at depth and high rock-stress environments can induce unanticipated dynamic rockmass deformation, posing a serious risk to the workforce. Time-trend analysis of certain seismological parameters has been used for many years to produce daily workplace seismic risk ratings which are meant to characterise rockmass behaviour and enable the identification of developing or imminent rock instability, allowing timeous ameliorating action to be taken – pro-actively and successfully. The impracticality of the daily reviewing of dozens of prior user-defined data selection polygons has meant that often an inappropriate assessment of the seismic hazard is done. Depending on the methodology or application of data analysis and interpretation, some of the information may not be relevant and even detract from the objective. By using the spatial event clusters associated with active workplaces to define the shape and size of the polygons for data selection for subsequent analysis, a problematic subjective component can be eliminated. | seismicity, risk, warning, short-term, ratings
T04: Deep mining and tunnellingRicardo Isidro FERREIRA, Richard MASETHE, Pinkie NDABASibanye-Stillwater, South AfricaRationale for the quick withdrawal of the underground workforce following (large) dynamic ground motions – how extensive should the exclusion zone be?1615 The mining of the tabular auriferous reefs on the rim of the Witwatersrand Basin in South Africa is very extensive, and even within individual mines, underground workplaces are often widespread. There is just cause not to evacuate an entire operation’s workforce following the unanticipated occurrence of a large mining-induced seismic event. We present the rationale for the quick withdrawal of the possibly affected underground workforce following such seismic events and the calculation methodology based on the damaging peak particle velocities (PPV) of the past seismicity. A minimum PPV from the source at which observable damage to the underground excavations is no longer apparent was inferred. The radii from the source within which ground velocities exceed this amount are then calculated for all recorded events with local magnitudes ML1.0 and greater. Those workplaces located within these negatively affected volumes are deemed at risk and the workforce is withdrawn. | seismicity, risk, workforce, evacuation, safety
T09: Long term behaviour of underground structuresAli RAZGORDANISHARAHI (1), Maximilian SORGNER (1), Adolf Bernd MORITZ (2), Thomas PILGERSTORFER (3), Bernhard L.A. PICHLER (1), Christian HELLMICH (1)1: Institute for Mechanics of Materials and Structures, TU Wien (Vienna University of Technology), Vienna, Austria; 2: OeBB-Infrastructure AG, Graz, Austria; 3: Geoconsult ZT GmbH, AustriaInvestigating the impact of viscoelastic material models for accurate stress estimation in precast concrete tunnel segments1616 The segmental tunnel lining of Koralmtunnel in Austria is equipped with state-of-the-art structural health monitoring methods. Vibrating wire strain gauges measure histories of normal strains at specific locations along the steel reinforcement of precast concrete tubbings. To translate these strains into normal stresses, viscoelastic behavior of concrete needs to be considered, and a Boltzmann-type convolution integral needs to be solved. In order to quantify the needed relaxation function of concrete, its creep function is represented in a format that distinguishes between short-term and long-term portions, linked to a power law and logarithmic law, respectively. This function is converted into the corresponding relaxation function. It allows for translating measured strain histories into stress evolutions. It is shown that accounting for relaxation of concrete is crucial for long-term stress quantification in segmental tunnel linings. Linear elastically quantified stresses overestimate linear visco-elastically quantified stresses by 75% already three years after tunnel ring installation. | precast concrete, viscoelastic material model, creep function, strain measurements, strain gauges
T06: Geological investigation and characterizationHalil KUMSAR (1), Ömer AYDAN (2), Hitoshi MATSUBARA (2), Kouki MORI (2)1: Pamukkale University, Turkey; 2: University of the Ryukyus, JapanCharacteristics of hydro-magnesite of Salda Lake (Türkiye) and their implications on rocks of Jezerro Crater in Mars1617 Hydro-magnesite formation in Salda Lake in Türkiye receive great attention as an example on Earth in relation to the early life traces in the Jezerro Crater of Mars. The authors investigated Salda Lake and sampled hydro-magnesite. The sampled stromatolites vary newly formed soft ones to quite hardened ones. Microscopic structures and X-Ray analyses of samples were used to characterize the minerological constitutents. Some samples were prepared from large pieces of stromatolites to determine physico-mechanical properties. The investigation results are presented and the implications of the outcomes from these investigations on the characteristics of rocks in Jezerro Crater in Mars are discussed. | Salda Lake, hydro-magnesite, physico-mechanical properties, stromatolite, X-Ray analyses
T05: Digitalization & AutomatisationJian LIU (1), Aohui OUYANG (1,3), Omar ALDAJANI (2), Zili LI (1,2), Herbert EINSTEIN (2)1: University College Cork, Ireland; 2: Massachusetts Institute of Technology; 3: The European Organization for Nuclear Research (CERN)Automatic Fracture Extraction in Laboratory Rock Sample using Deep Learning method1621 Fractures play a crucial role in the hydromechanical behavior of rocks. To investigate the fundamental fracturing mechanism, the imagery of hydraulic fracture evolution is captured in laboratory testing of rock specimens. Conventionally, temporal-spatial characteristics of rock fractures must be identified and extracted manually or by image processing techniques (IPTs) for interpretation, requiring enormous time and labor with low accuracy. This paper develops a deep learning-based method that quickly and automatically identifies and extracts hydraulically induced fractures in rock specimens at the pixel level. The applicability of this method is validated through image datasets from hydraulic fracturing tests. This method shows better effectiveness and efficiency than previous IPTs. The accuracy of the deep learning method reaches 99 percent and the average processing speed is only 389 ms per image when adopting an NVIDIA Tesla T4 GPU, saving a large amount of time compared to human work. | deep learning, hydraulic fracture, fracture extraction, image processing
T01: Challenging rock engineering projectsStefan SKUK, Harald EGGER, Emanuele BARNABEI, Umberto Marco CONTI, Giuseppe FODERÀ, Gianluca LIUZZI, Gianluca MAGGIO, Davide RENGHI, Antonio SPAZIANI, Antonio VOZABBT Brenner Base Tunnel, ItalyBrenner Base Tunnel: three DS-TBMs excavating in parallel under the Alps in Italy – Findings, difficulties and achievements from a geological-geotechnical point of view1623 The Brenner Base Tunnel is a railway connection running beneath the Italian and Austrian Alps for 64 km under high overburdens. In the Italian lot Mules 2-3 a 14 km long stretch of the Exploratory Tunnel has been completed by a DS-TBM with a diameter of 6.85 m and two twin DS-TBMs are currently excavating the Main Tunnels, which are of equal length but have a diameter of 10.71 m. The geological context consists of metamorphic geological units ranging from gneiss, micaschists, phyllites to marbles and intercalations of evaporitic units. About 21 significant fault zones were crossed. Due to different geological factors four standstills occurred in the Exploratory Tunnel, six in the western and two in the eastern Main Tunnels. In order to early detect and manage these critical zones, an accurate geological forecast, advance explorations, geological documentation and a continuous analysis of the machine and monitoring data are required. | Brenner Base Tunnel, Double Shield Tunnel Boring Machine (DS-TBM), Exploratory Tunnel (ET), Main tunnels (MT-W, MT-E), High Overburden, Geological documentation
T05: Digitalization & AutomatisationTushar BHANDARI, Debasis DEB, Chamanth Sai Reddy VEMULAPATIIndian Institute of Technology, Kharagpur, IndiaGlobal Unstructured Digital Image Correlation for determining strains around circular opening1625 Digital Image Correlation (DIC) is a non-contact displacement measurement method that uses image correlation algorithms to measure displacement. The algorithms used are often designed for structures having uniform geometry without cavities. However, in the rock engineering problems irregular geometry and cavities are common. Therefore, an unstructured finite element based DIC (FE-DIC) algorithm is developed, which can incorporate specimens with curved geometries, and cavities. The mathematical principles behind the algorithm are discussed briefly. The validation of the developed algorithm is conducted using a deformed image created using displacements based on the Kirsch solution. The algorithm is also employed to calculate displacement field and strain visualization around a circular cavity in a concrete specimen under compressive loading conditions. The results demonstrate the potential of the unstructured FE-DIC algorithm in providing insights into the material deformation and failure behavior in the specimens. | DIC, Unstructured Mesh, Circular Cavity, Strain Visualization, Kirsch Solution
T15: Rock and rock mass propertiesReza MOTTAGHI, Zhongwei CHEN, David J. WILLIAM, Mehdi SERATIThe University of Queensland, Brisbane, AustraliaExperimental and Numerical Investigations on Bi-axial Loading of Sandstone Brazilian Disks1626 The behavior of sandstone Brazilian disks is investigated under loading in two perpendicular directions. The vertical force was applied at a rate of 200 N/sec while the horizontal load was adjusted to a predetermined ratio of the vertical load until the sample failure. This testing process was repeated for various ratios (including 0%, 10%, 20%, 25%, 33%, 40%, 45%, and 50%) and the failure of samples were captured using a high-speed camera at 25 kHz. While the superposition theory suggests that there will be no tension at the center of the disks in a biaxial loading mode for ratios of 33% and above, results suggest tensile crack occurrence for ratios up to 45%. The numerical results further show that there is always a tensile stress close to the Indirect Tensile Strength happening within the disks central line. It was also noted that if the material transitions into a plastic mode due to extremely high stress ratios, the induced tensile stress would be always considerably higher. | Bi-axial Brazilian tests, Indirect tensile test, Bi-axial loading, Finite element modeling
T15: Rock and rock mass propertiesLucía CONDE-FERNÁNDEZ (1), Víctor MARTÍNEZ-IBÁÑEZ (2), Martina-Inmaculada ÁLVAREZ-FERNÁNDEZ (1), María-Elvira GARRIDO-DE LA TORRE (2), Celestino GONZÁLEZ-NICIEZA (1), Carlos HIDALGO-SIGNES (2)1: University of Oviedo, Spain; 2: Universitat Politècnica de València, SpainEffect of temperature on the mechanical behavior and acoustic emission characteristics of a rock – like material1627 Acoustic Emission (AE) is a non – destructive testing technique that allows the recording of the elastic waves released during crack propagation when materials are subjected to different stresses. Most of the current research evaluates AE characteristics related to mechanically stressed materials. However, there are hardly any references to studies that target how thermal or thermos – mechanical stresses influence AE recordings. Consequently, an experimental campaign has been designed to characterize high–strength mortar specimens, subjected to different temperatures while performing simple compression tests and monitoring the AE. The research has allowed obtaining interesting results in line with the objectives set for this study. Thus, it has been possible to establish that: 1) temperature affects the simple compressive strength of the material studied, 2) the recording of AE associated with thermal stresses is possible and 3) the combination of thermal and mechanical stresses increases the recording of AE parameters. | Acoustic Emission (AE), thermo-mechanical stresses, crack propagation, temperature
T14: Petroleum engineering and carbon sequestrationYuhao LIU (1), Fengshou ZHANG (1), Dingwei WENG (2), Hongbo LIANG (2), Chunming HE (2)1: Department of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai, China; 2: Research Institute of Petroleum Exploration & Development, PetroChina, Beijing, ChinaNumerical investigations on THM coupled process during water flooding with multiple well patterns under non-isothermal two phase flow1628 A three-dimensional numerical model of non-isothermal two-phase flow in the deformable porous medium during water flooding is described in this paper. Based on the thermal-hydro-mechanical (THM) coupling theory, governing equations of oil-water two-phase flow are integrated additionally and implemented into the open-source finite element framework OpenGeoSys. Temperature-dependent fluid viscosity and fluid density, along with strain-dependent reservoir permeability are also considered. With different well patterns, stress and pore pressure distribution, heat transfer and the flow of injected water in the reservoir during ten years of injection are simulated. According to the numerical results, high temperature can promote fluid flow to improve the treatment performance. Cold water injection causes the normal stress reduction by introducing significant thermal stress. Spatial variation of stress, pore pressure and injected water saturation are affected by different well pattern scenarios. This finding has important consequences in the field operation of water flooding under the environment of large reservoir depth and high temperature. | Water flooding, THM coupling, Two phase flow, Multiple well patterns, OpenGeoSys
T06: Geological investigation and characterizationErlend SKRETTING, Georg H. ERHARTER, Jessica Ka Yi CHIUNorwegian Geotechnical Institute (NGI), NorwayVirtual reality based uncertainty assessment of rock mass characterization of tunnel faces1629 Rock mass characterization has a high degree of uncertainty due to difficulties in capturing the heterogeneity of the rock mass, and due to human subjectivity and biases while mapping. Since classification systems are often used as a tool to decide rock support design, misinterpretation of the rock mass can lead to an inadequate support design. In this study, 3D-scans of tunnel faces are implemented in virtual reality (VR) to investigate the uncertainty of tunnel face mapping. A VR-mapping survey is conducted where 14 professional and experienced engineering geologists have performed Q-system based tunnel face mapping and the results allow to quantify the uncertainty related to that process, as well as investigating the different psychological aspects that influence engineering geologists in the mapping process. The paper closes with a discussion about what this VR-study's results mean with respect to rock mass classification and possible future applications for VR in rock engineering. | Rock mass characterization, tunnel face mapping, virtual reality (VR), rock mass classification systems, Q-system, uncertainty
T05: Digitalization & AutomatisationEngin USTA, Kamran ESMAEILIMine Modeling and Analytics Lab, Department of Civil and Mineral Engineering, University of Toronto, CanadaJoint surface characterization using manual and multi-sensor core logging systems1630 The shear behavior of a discontinuity can be significantly influenced by its surface characteristics. This paper compares manual and sensor-based geotechnical core logging methods for joint surface characterization. More than 500 m of core samples were logged, in which 367 joints were both digitally and manually characterized. Manual logging was carried out by visually assessing joint surface roughness and alteration indices. Sensor-based logging includes creating 2D and 3D joint roughness profiles using a handheld 3D scanner and measuring joint wall hardness and alteration type using Equotip Leeb hardness and pXRF analyzer. The collected data were statistically analyzed. A comparison between manual and multi-sensor joint surface characterization was made to demonstrate the discrepancy between the manual and digital logging techniques regarding joint surface roughness, joint wall strength and joint alteration. | Joint surface characterization, Multi-sensor core logging, Leeb hardness test, Joint alteration, Joint roughness, 3D handheld scanner
T06: Geological investigation and characterizationMadelyn SUMNER, Laura PYRAK-NOLTEPurdue University, United States of AmericaVisualization of Fracture Intersections from 3D X-ray Imaging1631 Though fracture intersections control the connectivity of a fracture network, few studies have examined the deformation of intersections. A laboratory study was performed to examine the effect of an applied stress on a fracture network and the intersection geometry. 3D printing was used to create 2 orthogonal intersecting fractures with either a “+” or “x” orientation relative to an applied vertical load. 3D X-ray microscopy was used to image the fracture network. For the “+” orientation, the network connectivity was maintained by the vertical fracture that did not deform significantly under load. However, for the “x” orientation, the void volume and connectivity between the two fractures decreased significantly and almost ceased to exist at the highest load as the topology transitioned from “X” to “Z” to “V”. Hydro-mechanical modeling of fracture networks may need to account for changes in intersection connectivity from perturbations in stress. | Fracture networks, fracture intersections, apertures, stress, imaging
T15: Rock and rock mass propertiesSarbartha SARKAR, Rakesh KUMARIndian Institute of Technology Kharagpur, IndiaCharacterization of Mobilized Cohesion, Friction and Dilation Angles of Brittle Rock During Plastic Deformation1632 The behavior of basalt rock in plastic region is investigated by tri-axial compression tests. Four sets of basalt rocks are tested using a servo-controlled universal testing machine (UTM) under three confining stress 2, 4, 6 MPa. This study generates valuable information of post-yielding parameters like cohesion, friction and dilation angles of brittle rocks and shows their behavior during plastic deformation. The analysis results show that in post peak region, the basalt rock is brittle in nature. It exhibits a negative exponential relationship of cohesion and dilation angle with plastic shear strain. However, the friction angle remains almost constant with increase of plastic shear strain. The existing dilation angle models of Zhao & Cai (2010) and Pourhosseini & Shabanimashcool (2014) are used for estimating the model parameters for basalt rock. It is found that Zhao & Cai (2010) is more aptly fitted for basalt rock. | Brittle rock, cohesion, peak dilation angle, plastic shear strain
T05: Digitalization & AutomatisationAlla SAPRONOVA (1), Kazuo SAKAI (2), Shuntaro MIYANAGA (2), Paul Johannes UNTERLASS (1), Abdallah Ahmed Fouad Elsayed SOLIMAN (1), Thomas MARCHER (1)1: Institute of Rock Mechanics and Tunnelling, University of Technology Graz, Austria; 2: Geotechnical Research Section, Infrastructure Technology Research Department, Taisei Advance Center of TechnologyMWD data analysis for optimization of tunnel excavation1633 The drill and blast tunneling method applies to various rock mass conditions and is widely used in underground construction. Optimization of drill and blast requires careful planning and currently depends on the engineers’ ability to execute the art of blasting. Intelligent analysis of measurement while drilling (MWD) data from blast holes can be used for process optimizations, responsible resource utilization, and risk minimization. For example, an Artificial Intelligence (AI) -based decision support system (DSS) can suggest the volume and content of explosive material. However, to develop a reliable and trustworthy DSS, one needs to understand the relation between MWD data logs and the underlying lithology conditions, like composition or type of rock mass. This work provides an overview of the most common methods for MWD data analysis. Selected methods are then utilized to develop predictive machine-learning (ML) models, which are further validated with available MWD data. | data analysis, MWD data, optimization, machine learning
T17: Rock slope engineeringSuryajyoti NANDA, Satyam CHOUDHURY, Shantanu PATELIndian Institute of Technology Kharagpur, West Bengal, IndiaAssessment of structurally-controlled slope failure in a steeply dipping Iron ore mine1635 Excavating an open pit mine with a steep angle considering both productivity and safety is a major challenge. The current work proposes a framework for slope design for a large open-pit iron ore mine with complex geological conditions. The joint properties of the steeply deposited mine are collected through face mapping and laboratory tests are done to obtain the intact rock and joint properties. The kinematic analysis of the initial slope design showed wedges forming in the benches. As a remedial measure, the wedge failure analysis is done for the bench scale and the most suitable pit design is selected by changing the slope angle and pit orientation. It was found that the optimized slope design in terms of both safety and productivity can be achieved at an overall slope angle of around 350 with a stripping ratio of approximately 3.5. | Pit slope design, Face mapping, Kinematic analysis, Wedge failure, Stripping ratio
T05: Digitalization & AutomatisationHaojun PANG, Fei JIA, Yingcai HOU, Feipeng HUANG, Yadong XUEDepartment of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai, ChinaIntelligent risk management for TBM hard rock tunnelling based on Knowledge Graph1638 Tunnel construction using TBM involves various factors that increase risks to the structure, including workers, machinery, operation, structure and surrounding environment. These factors interact in complex ways, making risk management rather complicated and challenging. To achieve a better risk management, state-of-the-art technologies such as knowledge graph (KG) can help manage construction risk by storing, managing and mining risk concepts and construction entities. In the paper, a risk management knowledge graph was created for the TBM hard rock tunnel constructed in West China using Neo4j graph database. Work breakdown tree (WBS) and risk breakdown tree (RBS) were created to subdivide the complex TBM tunnelling process and risk sources. WBS and RBS entities were then integrated into the knowledge graph, making the attributes and relations of various entities clear to engineers. The case study demonstrated that knowledge graph is effective, reliable and advanced in TBM hard rock tunnelling risk management. | TBM tunnelling, hard rock, risk management, knowledge graph, work breakdown structure, risk breakdown structure
T01: Challenging rock engineering projectsOskar Leonard VAN DER WEIJ (1), Daniele MARTINELLI (2)1: Kalliosuunnittelu Oy Rockplan Ltd, Finland; 2: Politecnico di Torino, Torino, ItalyExtensive sensitivity analysis of the Kivenlahti metro center using DEM1639 The Kivenlahti metro center is a combined residential and commercial building complex designed on top of a metro station in Espoo, Finland. Rock mechanical modelling was carried out using 3DEC to ensure the integrity of the metro station. A detailed sensitivity analysis was conducted consisting of simulating the effects of reduced horizontal in-situ stress, increased loading and weaker rock mass. Whilst the base case scenario confirmed that the proposed design should not lead to critical deformations within the metro station, the results of the sensitivity analysis indicated vulnerable locations if the loading is increased from the current design. An in-situ stress significantly lower than expected could lead to critical deformations within the metro station. Whilst the sensitivity analysis was conducted using extreme values, it successfully demonstrated areas for concern and thus aided in designing measures for mitigating the risks for the metro station. | DEM, 3DEC, sensitivity analysis, metro station
T16: Underground storage for liquid and gaseous mediaKarl-Heinz LUX, Tianjie PAN, Ralf WOLTERS, Jörg FEIERABENDClausthal University of Technology, GermanyConversion of existing natural gas storage caverns for hydrogen storage – some selected aspects to be considered1640 The conversion of existing natural gas storage caverns for hydrogen storage requires the assessment of the mechanical integrity of the wellbore. The additional impact on the wellbore induced by cavern convergence due to long-term operation must be particularly considered. Numerical simulations of an existing cavern and its wellbore using the FTK-simulator are performed to investigate the stress and strain changes in the casing shoe, including casing, annulus cement, and contact interfaces during the operation. In addition, hydrogen transport in the casing shoe area at the borehole contour is numerically simulated during the mechanical integrity test. It is shown that the FTK-simulator can be successfully used to predict the TH2M-couped load-bearing behavior of salt cavern and wellbore throughout its entire life and provides a detailed insight into the development of stress and strain regarding the casing, annulus cement, and contact interfaces. | underground hydrogen storage, salt caverns, well integrity, mechanical integrity test
T05: Digitalization & AutomatisationAlla SAPRONOVA, Paul Johannes UNTERLASS, Vaibhav SHRINGI, Thomas MARCHERInstitute of Rock Mechanics and Tunnelling, Graz University of Technology, AustriaTowards the development of a harmonized inventory database for decision support: automatized information extraction1641 Decisions made during tunnel construction are based on the opinion of safety-oriented engineers and utilize the knowledge of human experts. Because every tunnel is unique to some extent, it can be assumed that experts' decisions are often "reinvented" on-site. Given the number of completed, ongoing, and planned tunnel projects, it is possible to identify projects which could be used as an extra reference to assist the decision-making processes for new constructions. For human experts it is difficult and time-consuming to identify all similar reference projects. Aiming at developing a harmonized inventory database for decision support (DS) during the planning and construction phases, this work discusses a pathway for retrieving and processing data from archived projects. The major steps for information extraction are described, and the process of developing a harmonized database is discussed. This work specifically addresses the process of extracting tabular information from images using machine learning methods. | data analysis, information extraction, technical documentation, decision support
T06: Geological investigation and characterizationMichelle PIENAAR (1), Raymond DURRHEIM (2), Musa MANZI (2), Glen NWAILA (2), Hennie GROBLER (3), Thabang KGARUME (4), Dean PRETORIUS (4), Michael VAN SCHOOR (4), Abrie OBERHOLSTER (5)1: Mandela Mining Precinct, South Africa; 2: University of the Witwatersrand, South Africa; 3: University of Johannesburg, South Africa; 4: CSIR, South Africa; 5: University of Pretoria, South AfricaMitigating the rock fall and rockburst risk in South African gold and platinum mines through advanced knowledge of the ore body1646 The Mandela Mining Precinct was launched in 2018 with the goal of modernizing the South African mining industry. It comprises three major initiatives that seek to improve efficiency, health and safety in current mining operations; develop fully mechanized systems to mine narrow tabular ore bodies in hard rock; and develop non-explosive rock-breaking systems. The crosscutting Advanced Orebody Knowledge (AOK) program seeks to develop technologies to characterize the rock mass ahead of mining and identify potentially hazardous geological features. Mining methods, layouts and rock support systems will be adjusted accordingly to mitigate the risk of rock falls and bursts. Technologies include rock drilling, light detection and ranging (LiDAR), ground penetrating radar (GPR), electrical resistance tomography (ERT), and various acoustic, thermographic and seismic techniques. Machine learning methods are being implemented to improve data processing and interpretation. This paper describes the status of the research program at 31 May 2023. | rock fall, rockburst, LiDAR, GPR, ERT, thermography, seismics
T17: Rock slope engineeringCarlos Luis GARRIDO GARRIDO, Sergio SÁNCHEZ RODRÍGUEZ, Paula DEL POZO GARCÍAAECOM. Enterprise Capabilities EuropeInteraction between tunnels and slopes. Analysis of weak rock masses considering the Hoek-Brown failure criterion1647 Primary support design for tunnels close to a slope should consider the existing asymmetric stress state. Tunnel excavation imposes deconfinement around the cavity, which may affect the available margin of safety of the slope. For fair to good rock masses, the impact on the existing slope is mostly conditioned by the rock mass structure, even for shallow tunnels. This research is focused on analyzing the impact on the primary support needs for openings in weak rock masses, as well as the potential changes in the stability conditions of the slopes caused by shallow tunnels excavated near them. The Hoek-Brown failure criterion has been used for the parametric study carried out by means of numerical analysis. With these numerical simulations, the construction process of the tunnel is studied to analyze its influence on the existing slope stability, along with the corresponding effects on the support needs for different rock mass conditions. | Tunnel-slope interaction, slope stability, factor of safety, weak rock masses, Hoek-Brown failure criterion, numerical models
T05: Digitalization & AutomatisationYerkezhan MADENOVA (1,2), Fidelis SUORINENI (1), Shuai XU (3)1: Nazarbayev University, Astana, Kazakhstan; 2: Los Alamos National Laboratory, Los Alamos, NM, USA (Current); 3: Northeastern University, Shenyang, People's Republic of ChinaAutomated and digitalized web tool for open stope design1648 The Stability Graph is a widely used method for open stope design to control dilution in underground mining. The method considers several factors, which are determined from different empirical graphs and require additional computations. The manual application of the Stability Graph is time-consuming and has the potential to cause computational and human subjectivity errors in open stope stability prediction. The Stability Graph is developed empirically, and its reliability increases with increased data size and quality. However, its current application does not allow data sharing between practitioners that use the method in the mining industry. This work presents the digital analogous of the Stability Graph method through a web application, which is built to ease its use and eliminate limitations. The web-based tool for open stope design is named StopeSoft and is available at openstope.com. StopeSoft provides several benefits to users compared to the traditional Stability Graph including case history data sharing. | Open stope, Stability Graph, StopeSoft web tool, automation, digitalization
T01: Challenging rock engineering projectsLorenzo BATOCCHIONI, Valeria GONZALEZ RODRIGUEZ, Salvatore MILIZIANOSapienza University of Rome, ItalySoil-structure interaction of preliminary deformable lining for conventional tunnel in squeezing conditions using HiDSte elements1649 The construction of deep tunnels is continuously increasing due to both economic and environmental reasons. High cover and poor geotechnical ground make the construction of tunnels difficult (squeezing conditions). Due to the high loads transmitted by the ground, the preliminary lining can be rarely designed following the so-called resistance principle. The state of the art suggests approaching the lining design by allowing the development of the necessary convergences to adequately reduce the rock load (yielding principle). In this paper, a new steel element (HiDSte), yet to be employed in real tunnel works, is described. The behaviour of the lining made of steel ribs along the HiDSte is illustrated through 2D numerical analyses. The numerical results allowed the evaluation of the peculiar way soil and lining interact and, more in general, the ability of the yielding lining to reduce the in-situ stress level undergone by the lining. | Conventional tunnelling, squeezing conditions, yielding principle, preliminary lining with elastoplastic elements, soil-structure interaction
T07: Geological risks and natural hazardsGiulia TORSELLO (1), Marta CASTELLI (1), Michele MORELLI (2)1: Politecnico di Torino, Italy; 2: ARPA Piemonte, Regional Agency for the Protection of the Environment, Turin, ItalyThe collapse of Torrione Sucai (Mt. Viso, Italy): rockfall analysis and data calibration1650 In December 2019 a large collapse affected the Torrione Sucai, a rocky structure located on the North-Eastern slope of Mt. Viso (Italy) at about 3100 m a.s.l. Mt Viso has been included in the UNESCO World Heritage Sites since 2013 as a biosphere reserve. Therefore, hazard and risk assessment is a priority for the protection of people and the environment. The rockfall was triggered by a combination of high fracturing of the rock mass and permafrost degradation, with associated phenomena that weakened the rock mass and created conditions for slope instability. This study entails a multi-scale analysis of fracture distribution and intersections, in order to identify the zones most prone to collapse. Moreover, a multi-scale back analysis of the run-out behavior of the 2019 rockfall was performed. The results were used to calibrate preliminary susceptibility analyses for the entire area, presented and discussed in the paper. | climate change, permafrost degradation, rockfall, Italian Alps, Mt. Viso
T15: Rock and rock mass propertiesPeter ALLAN (1), Jean-Pierre BAUD (2), Robert HEINTZ (3)1: Pace Geotechnics, Morpeth, Northumberland, United Kingdom; 2: Eurogéo, France; 3: Eurasol, LuxembourgHard soil and rock classification – Pressuremeter data versus tests on samples1651 This paper deals with the correlation between rock properties presented by Kanji (2014), Kanji & Leão (2020) on rock samples of a wide range of strengths, with the classification of indurated and rocky soils from pressuremeter diagrams by Baud & Gambin (2013), Baud (2021). Tests were carried out simultaneously on a same jobsite, and these two approaches contribute to the characterization of rock drillability, showing a certain degree of similarity between them. The relationship between the pressuremeter modulus of the rock mass (ISO 22476-5) and a Young's modulus usable for finite element software is a stumbling block for the validation of a rock model, which remains questionable, as the actual behaviour of the rock masses is highly non-linear. Neither in-situ expansion testing nor uniaxial compression testing directly measures a single modulus representative of the rock mass, so engineering practice is to apply one or more weighting factors, primarily considering the spacing and nature of fractures within the rock mass. | Rocks classification, High Pressure Pressuremeter Test (Dilatometer Test), Compression Strength, Ground Modulus, Drillability
T04: Deep mining and tunnellingRodolfo Enrique CABEZAS (1), Adeline DELONCA (2)1: SRK Consulting, Chile; 2: Universidad Técnica Federico Santa María, ChileReliability of Predicting damage in hard rock mass around deep tunnels in terms of its convergence1653 In deep excavations, mechanical instabilities may appear, inducing damage to the rock mass. These instabilities may be difficult to identify but are inferred as convergence of the walls over time. This magnitude and evolution may provide valuable information for tunnel stability analysis, as the extent of the damage affects where the ground support is installed. This study proposes a simple model to relate convergence with the depth of failure within the rock mass. A normalized damage curve is obtained as a function of the total deformation measured, for compressed and tensile areas around the excavation. The parameters are defined according to the stress state and the strength properties of the rock mass. The influence of the variability of the properties is considered, extending the analysis to a probabilistic case using Montecarlo method and obtaining reliability ranges for different rock masses expected in deep orebodies, for example in hydrothermally altered conditions. | Deep mining, tunneling, Damage, Depth of failure, Reliability
T05: Digitalization & AutomatisationZhansaya MAKSUT, Rakhat MEIRAMOV, Adnan YAZICI, Fidelis SUORINENINazarbayev University, KazakhstanA Machine Learning-based Microseismic Event Location and Wave Velocity Prediction1654 Human-induced seismicity in underground mining has significant impacts on productivity, safety, and operating costs. Accurate predictors for microseismic event sources are crucial to minimize disasters such as rockbursts. This study develops machine learning algorithms to predict real-time seismic wave velocities in deteriorating underground mines, using data from Nazarbayev University's School of Mining and Geosciences laboratory. Traditional constant velocity models are imprecise, so the study explores several machine learning models. The best-performing model was Gradient Boosted Decision Tree with an MAE of 7.146 m/s. These findings demonstrate that machine learning algorithms can accurately predict seismic wave velocities in underground mining environments. | neural network, decision tree, regression, rockbursts, wave velocity
T13: Numerical methods in rock engineeringAbolfazl ABDOLLAHIPOUR (2), Mohammad FATEHI MARJI (1), Rezvan ALIZADEH (1), Manouchehr SANEI (1)1: Department of Mining and Metallurgy, Faculty of Engineering, Yazd University, Islamic Republic of Iran; 2: School of Mining Engineering, College of Engineering, University of Tehran, Tehran, IranNumerical simulation of rock’s fatigue behavior using a modified indirect boundary element method1655 Fatigue crack growth in brittle rocks was numerically simulated by a modified displacement discontinuity method. Mode I and Mode II stress intensity factors and their increments due to cyclic loading of brittle rock samples were numerically estimated using linear elastic fracture mechanics. Effective methodologies were introduced for modeling the fatigue crack propagation in brittle rocks under cyclic loading. The quadratic displacement discontinuity and crack tip elements were used to predict the mixed mode stress intensity factors at crack tips in the brittle material specimens. The maximum tangential stress criterion was used to predict the crack growth paths using the incrementally increasing cracks lengths in the predicted direction. Several examples were solved to evaluate the accuracy and efficiency of the proposed algorithm. It is concluded that the fatigue crack growth in brittle rocks under mixed-mode loading conditions can be effectively analyzed by the modified higher order displacement discontinuity. | Fatigue crack growth, Boundary element method, Higher order displacement discontinuity, Crack tip elements, Maximum tangential stress criterion
T06: Geological investigation and characterizationJunxiong YANG, Sebastian D. GOODFELLOW, John P. HARRISONUniversity of Toronto, Toronto, CanadaUsing borehole breakout data to constrain the in situ stress tensor1656 Knowledge of the in situ stress state is critical for underground rock engineering projects, but direct measurement data are often not available. Although borehole breakouts are only indicative of the in situ stress state, they nevertheless represent a significant data resource. Properties such as breakout orientation, width and depth can all potentially be used to constrain the in situ stress state. In this paper, we present a novel global optimization and associated objective function that uses breakout data to constrain the normalized in situ stress tensor. This tensor is one in which the magnitudes of the three principal stresses are normalized with respect to the difference between the maximum and the minimum principal stresses, and three Tait–Bryan angles describe the principal stress orientations. The efficacy of the scheme is demonstrated by applying it to breakout data obtained from deep mining operations in the Sudbury mining district of Ontario, Canada. | borehole breakout, in situ stress, global optimization, normalized principal stresses, principal stress orientations
T07: Geological risks and natural hazardsJeoung Seok YOON (1,2), Anne STRADER (1), Jian ZHOU (3), Soo-Gin KIM (4), Jae-Yeol CHEONG (4)1: DynaFrax UG, limited liability, Germany; 2: Handong Global University, Korea; 3: Beijing University of Technology, China; 4: Korea Radioactive Waste Agency, KoreaNumerical Modelling Study of the 2016 Gyeongju Earthquake Rupture Process and Correlation with Groundwater Level Change1660 Coseismic changes in groundwater level have been reported worldwide, particularly in areas of moderate to high seismicity. These variations are often attributed to redistribution of stress and strain, which can reactivate fractures, joints and microcracks through local changes in fluid pressure. Such variations were observed following the September 2016 ML 5.8 Gyeongju earthquake in South Korea, rupturing the Yangsan fault at a depth of 11–16 km and producing strong high-frequency ground motions. To better understand and quantify local stress changes and subsequent changes in fluid migration patterns within this area, we have developed a discrete element model (DEM) of the Yangsan fault network using the Particle Flow Code (PFC2D) software. Spatial distributions of local Coulomb stress changes are in good agreement with stress changes reported in literature. Furthermore, a weak but positive correlation is observed between the amount of groundwater level change and increased stress. | Discrete element model, numerical modeling, rupture simulation, Korean seismicity, fluid migration
T14: Petroleum engineering and carbon sequestrationZhao FENG (1), Fengshou ZHANG (1), Xianda SHEN (2), Bichen YAN (3), Zhaowei CHEN (4)1: Department of Geotechnical Engineering, Tongji University, Shanghai, China; 2: Department of Civil and Environmental Engineering, Clarkson Univeristy, Potsdam, NY, USA; 3: Ali I. Al-Naimi Petroleum Engineering Research Center, Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia; 4: CNPC Drilling Research Institute, Beijing, ChinaA data-driven model for the prediction of stimulated reservoir volume (SRV) evolution during hydraulic fracturing1661 Accurate forecasting of stimulated reservoir volume (SRV) constitutes a key step in field evaluation and optimization during hydraulic fracturing. In this work, a data-driven model is developed to take advantage of field monitored microseismicity and fracturing parameters for predicting SRV ahead of time. A voxelized method is applied to calculate SRV values using recorded microseismicity data. Fracturing parameters along with SRV history are fed into a Long Short-Term Memory (LSTM) network as inputs. This model can successfully characterize the evolution of SRV. The LSTM network has excellent prediction accuracy (R2 > 0.80) at most stages while performing poorly at the initial stages. The influence of SRV history, time lag size and time window length is investigated to confirm the effectiveness of the proposed method. This study provides a new approach for unconventional reservoir hydraulic fracturing assessment using data-driven methods. | Stimulated reservoir volume, Hydraulic fracturing, Data-driven model, Long short-term memory network
T09: Long term behaviour of underground structuresRui HUANG (1,2), Takafumi SEIKI (1), Qinxi DONG (3), Shizuo NOGUCHI (4), Takeshi OHMURA (4)1: Utsunomiya University, Japan; 2: Xihua University, China; 3: Hainan University, China; 4: Kawasaki Geological Engineering Co. Ltd., JapanConsideration to evaluate maintenance process for utilization of non-supported underground quarries1662 In this study, the authors focus on propose evaluation chart for checking stability and safety the underground quarries because of the underground quarries are unstable and worried about the corrupts. Additionally, it is necessary for those users, such as entrepreneurs to evaluate the stability of the underground spaces in case of utilizing those underground spaces in certain purpose. Field survey is very important and necessary to understand for the workers and entrepreneurs. Thus, the authors consider the stress distribution and deformation to simulate active and abandoned underground quarries. the authors will consider stability for individual structure of room and pillar type based on the numerical analysis with considering influence of adjacent underground spaces. Finally, the authors will discuss the maintenance process to utilize the underground quarries analysis. | underground quarry, stability and utilization assessment, field survey, numerical analysis
T15: Rock and rock mass propertiesYousef NAVIDTEHRANI (1), Covadonga BETEGÓN (1), Robert W. ZIMMERMAN (2), Emilio MARTÍNEZ-PAÑEDA (2)1: University of Oviedo, Gijon, Spain; 2: Imperial College London, London, UKOn the crack initiation location in the Brazilian test: Griffith-based insight1663 We address the controversy surrounding the use of the Brazilian test to estimate the tensile strength of rock-like materials. Due to its indirect nature, the tensile strength is inferred from the critical load by assuming that cracking initiates at the centre of the sample. We combine finite element analysis with the failure envelope of the generalised Griffith criterion to establish the crack nucleation location, and map the conditions that result in the nucleation of a centre crack. The results reveal that the regime of validity of the Brazilian test is much smaller than previously assumed, with current practices and standards being often inappropriate. An experimental protocol is developed that enables obtaining a valid estimate of the material tensile strength, and a MATLAB App is provided to facilitate the uptake of this protocol. We demonstrate the usefulness of our protocol through examples of valid and invalid tests from the literature. | Rock mechanics, Brazilian test, Fracture, Finite element analysis, Griffith theory
T15: Rock and rock mass propertiesMasahiko OSADA, Koji OSAWA, Christina Putri WIDYANINGTYAS, Yota TOGASHISaitama University, JapanFundamental study on estimation of permeability at in-situ EDZ from pore air pressure response1665 In this paper, we report the results of measuring the pore air pressure response at an isolated space in a rock block while pressure changes are given within a pressure range slightly less than atmospheric pressure. The transient decay method and the oscillation method were adopted to estimate the permeability in the laboratory. In transient decay method, the pressure outside of the rock block reduce from atmospheric pressure to 930 hPa, and the pore air pressure inside the block is monitored. On the other hand, the oscillation method applies a fixed amplitude and fixed frequency with a pressure of 900 to 950 hPa. After analyzing the recorded data, the estimated permeability values from two methods were compared with the permeability determined from measurements of flow rate through a sample under a constant pressure gradient. | In-situ permeability test, Transient pulse test, Pore air pressure oscillation method, Intrinsic permeability, Excavation Damaged Zone (EDZ)
T16: Underground storage for liquid and gaseous mediaManouchehr SANEI, Mohammad FATEHI MARJIDepartment of Mining and Metallurgical Engineering, Yazd University, Yazd, IranInvestigating and evaluating the geomechanics of geological storage of hydrogen from methane decomposition1666 Without the use of fossil fuels, a large contribution to global development would certainly suffer. However, recent scientific developments and perspectives have made it possible to provide the required energy without carbon production, using renewable sources. While renewable energy sources may be a solution to reduce anthropogenic greenhouse gas emissions from fossil fuels, there are still many problems in this development path. Therefore, it is necessary to devise long-term storage to balance the intermittent supply and demand for this new technology. Hydrogen (H2) can be proposed as a suitable energy to achieve goals and meet the growing global energy demand. However, the successful implementation of a large-scale hydrogen-based economy requires large-scale storage. Therefore, in this research, the geomechanics of storage for H2 from methane decomposition and the works of the past in this field will be analyzed and reviewed, and scientific cases will be reported to do this. | Hydrogen, Underground hydrogen storage, Geomechanics, Numerical modeling, Experimental studies
T05: Digitalization & AutomatisationJunsu LEEM (1), Jineon KIM (1), Jiwon CHOI (1), Jae-Joon SONG (1,2)1: Seoul National Unviersity, Seoul, Korea; 2: Research Institute of Energy and ResourcesComparison of an underground rock face 3D modeling performance: SfM-MVS with optimum photographing settings and LiDAR technology1668 Structure-from-motion & multi-view-stereo (SfM-MVS) and light-detecting-and-ranging (LiDAR) are the representative methods to generate a 3D point cloud of a rock face. Both methods have pros and cons depending on the conditions including illumination, surveying time, resolution, accuracy, and cost. For application in underground space, SfM-MVS has been used less than LiDAR due to its lack of error pre-determination and ambiguity of photographing settings. Leem (2023) has developed a theoretical error prediction model for SfM-MVS and derived optimum photographing settings which minimize SfM-MVS error under light and time constraints. This work utilized the optimum photographing settings for the SfM-MVS and compared it with LiDAR when modeling a 70 m² rock face at an illumination of 25 lx within 5 minutes at a tunnel construction site (Yeoju-si, Korea). As a result, SfM-MVS could generate a point cloud with 20 times higher resolution and double accuracy at 10 times lower cost than LiDAR. | SfM (structure-from-motion), MVS (multi-view-stereo), camera settings, UAV flight method, underground digital survey, LiDAR (light-detecting-and-ranging)
T16: Underground storage for liquid and gaseous mediaZongze LI (1,2), Jinyang FAN (1), Marion FOURMEAU (2), Chao DU (1), Deyi JIANG (1), Daniel NELIAS (2)1: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, China; 2: Univ Lyon, INSA Lyon, CNRS, LaMCoS, UMR5259, Villeurbanne, FranceExperimental study on creep behavior of rock salt under complex stress paths1670 To study the effect of stress path on the creep behaviors of rock salt, multi-stage loading and unloading of confining pressure creep tests under constant axial pressure have been carried out on rock salt samples. The results as follows: (1) Confining pressure is the dominant factor of deformation and can effectively restrain the propagation of microcracks in rock salt. (2) Strain hardening behavior of rock salt samples is observed during the loading process. Internal stress with the property of self-weakening grows and changes constantly with loading time, and the time required for weakening is relevant to the stress state and loading history. (3) Creep of rock salt is caused by effective stress, which is the difference between differential stress and internal stress. Whether the initial creep stage occurs and the delay time to the entry of a steady-state creep stage is related to the loading path. | rock salt; creep tests; stress path; loading and unloading; deformation mechanism
T13: Numerical methods in rock engineeringMingfei YAN (1), Yan JIN (1), Yunhu LU (1), Zongyu LU (2)1: China University of Petroleum,Beijing, People's Republic of China; 2: PetroChina Xinjiang Oilfield Company, Karamay, ChinaNumerical Study of Brittle Characteristics of Deep Buried Conglomerate Based on Discrete Element Method1671 Hydraulic fracture has become one of the technical means for efficient development of oil and gas reservoirs, and the brittle rock damage characteristics are the key mechanical indicators for fracturing to form complex fracture networks. The current research on brittle rock characteristics is mainly focused on shale reservoirs, and there is a lack of systematic and in-depth understanding of the characteristics of anisotropic, strongly inhomogeneous conglomerates and their fine-scale damage mechanisms. Through drilling cores and indoor rock mechanics experiments, discrete particle simulation techniques are introduced to reproduce the microfracture expansion mechanism of deeply buried conglomerates, and the study shows that conglomerate brittleness is more sensitive to the surrounding pressure, particle size and volumetric block proportion. Based on the simulation results, the brittleness evaluation index of conglomerate formation is established, which has certain reference significance for understanding the brittle characteristics of deep conglomerate and field fracture design. | Conglomerate, Brittleness, Particle flow code(PFC), Microscopic, Evaluation method
T15: Rock and rock mass propertiesSamarjeet KUMAR, Aditi NUWAL, Shantanu Kumar PATELIndian Institute of Technology Kharagpur, IndiaUnderstanding the Microscopic Mechanisms of the bi-modular behavior of rock1672 Rocks when tested in both tension and compression show bi-modularity. Although the effect of all the factors contributing to the bi-modularity behavior is not fully understood, one of the main contributing factors is considered to be the presence of the micro-structure separating/joining the mineral grains. In this study, the effects of grain micro-structure on the modulus ratio are examined using the discrete element tool PFC2D for LdB granite and yellow sandstone. Extensive calibration was carried out to find out the intergranular micro properties of the mineral grains which produce the macroscopic response of the rocks. The role of inter-granular bond strength, initial microfractures present, and inter-granular bond stiffness were investigated. It was found that initial micro-fractures present in a rock sample is the main reason for producing the bi-modularity in rock and by considering it, crack initiation stress observed in the laboratory can be captured (~ 40% of UCS). | Rock bi-modularity, micromechanical grain properties, PFC, crack initiation stress
T15: Rock and rock mass propertiesMatej PETRUZALEK (1), Ali AMINZADEH (1), Vaclav VAVRYCUK (1,2), Zuzana JECHUMTALOVA (2), Petr KOLAR (2), Josef ROTT (3,4), Tomas LOKAJICEK (1)1: Institute of Geology of the Czech Academy of Sciences, Czech Republic; 2: Institute of Geophysics of the Czech Academy of Science, Czech Republic; 3: Faculty of Science, Charles University, Prague, Czech Republic; 4: Správa železnic, státní organizace, Czech RepublicMicro-fracturing in SCB test: Acoustic emission analysis1673 Mode I fracture toughness test was performed on the Cotta sandstone on semi-circular bend specimen in a symmetric geometry. The twenty-two channels were used for acoustic emission (AE) monitoring during the loading up to the failure. This study presents a detail AE analysis focused on the better understanding of micro-mechanisms leading to formation of fracture process zone (FPZ) and the following fracture propagation. The interpretation was based on the stress-induced changes in locations and source mechanisms of AEs. As a result, the micro-cracking can be divided into three following intervals: FPZ initiation, FPZ formation and fracture propagation. Each separate interval has its different AE characteristics that are presented in this paper. | Fracture process zone, Fracture propagation, Acoustic emission, Source mechanism, Moment tensor, Semi-circular bend test
T13: Numerical methods in rock engineeringSurabhi MAURYA (1), Dr. Gaurav TIWARI (2)1: Indian Institute of Technology Kanpur, India; 2: Indian Institute of Technology Kanpur, IndiaPolymorphic uncertainty modelling of rock properties coupled with combined probabilistic and non-probabilistic framework for rock tunnel stability analysis1674 A polymorphic uncertainty model is proposed considering the combined effect of aleatory and epistemic uncertainties of rock properties on the stability analysis of rock tunnels. The model incorporates fuzzy logic to represent epistemic uncertainties in the Geological Strength Index (GSI), transformational uncertainty of empirical models, systematic uncertainties due to discrepancy between field and laboratory conditions, and stochastic methods to represent aleatory uncertain properties. Further, detailed guidelines are proposed for the characterization and fuzzification of epistemic uncertain properties. An extended Convergence-Confinement Method (CCM) is proposed and illustrated by performing the stability analysis of a railway tunnel in Jammu and Kashmir, India under the framework of combined probabilistic and non-probabilistic methods. Further, the results obtained from the developed methodology were systematically compared with those of traditional reliability-based results and it was concluded that the proposed methodology is in order with the available input parameters having different uncertainty types. | Fuzzy approach; polymorphic uncertainty; probabilistic methods; non-probabilistic methods
T10: Monitoringİhsan ÖZKAN (1), Mehmet MESUTOĞLU (1), Mahmut Yasin ÇETINKAYA (2)1: Konya Technical University, Konya, Turkey; 2: Turkish Coal Enterprises (TKİ)-Ömerler Underground Coal Mine, Kütahya, TurkeyA new in-situ monitoring system to determine stability of underground coal pillar subjected to dynamic loading: electrical resistance measurement system (ERMS)1678 The electrical resistance measurement system (ERMS) was tried to be developed. The first in-situ applications were carried out in A6 panel in GLİ underground coal mine. As perpendicular to the pillar face, two parallel boreholes with 4 m long and interval 30 cm were drilled. The copper plates with a width of 200 mm and a thickness of 0.5 mm was wrapped on the measuring rod with 50 cm intervals and also soldered with copper wires. Then two rods were separately inserted into boreholes named as ERMS-#. In this way, 5 stations were installed with 5 m intervals. Measurements were carried out by ohmmeter using each electrical wire coming from the copper plates located at the same depth of boreholes. ERMS values measured on pillar subjected to dynamic loading due to longwall mining operations were shown that there were unstable in the first 2.5 m region of the pillar side. | Longwall coal mining, Coal pillar, In-situ measurement, Electrical resistance behavior
T09: Long term behaviour of underground structuresArka Jyoti DAS, Prabhat Kumar MANDAL, Ranjan KUMARCSIR-Central Institute of Mining and Fuel Research, Dhanbad, IndiaDesign of underground structures and support systems for extraction of inclined coal seam1680 Strata control problems are observed more in dipping coal seams than flat coal seams due to shearing effects, asymmetric failure and stress distribution in inclined rock strata. As most of the pillar strength formulae are derived for the conditions of flat coal pillars, their embracing in the stability analysis of inclined pillars may jeopardize the workings. In this study, inclined pillars are designed by using the strength formulae derived for the inclined pillars. The strength of pillars decreases with the increase in the dip of the coal seams and with the decrease in the acute-angle of the corners of the rhombus-shaped pillars. A parametric study is carried out to quantify the effect of inclination on the failure characteristics of inclined pillars and surrounding rock mass. Based on the study, an adequate size of pillars and an effective support system have been designed for a case study mine. | Inclined coal pillar strength, Dip angle, Yield zone, Asymmetric stress distribution, Support system
T06: Geological investigation and characterizationJayeeta DEY (1), Sujit ROY (1), Abdul MATIN (2)1: SRK Mining Services (India) Private Limited, Kolkata, India; 2: University of Calcutta, Kolkata, IndiaMapping of faults in underground mine by Sub Surface Profiling technology1682 Underground mines often experience roof collapse due to the presence of faults. While major faults are identified during exploration, many a time smaller faults remain unidentified. Underground mine approaching such unidentified faults may result in sudden roof fall and groundwater ingress. To resolve the issue, we utilized GPR based Sub-Surface Profiling technology that is capable of capturing fault related deformation features as anomalies. Results of SSP scanning and its interpretation from an underground coal mine in India is presented. Signatures from SSP are found useful in mapping fracture frequency, identifying fault core and damage zone, and helped assessing the degree of cataclasis. Regular SSP scanning helped predicting the rock conditions in advancing galleries and facilitated to adopt appropriate roof and water management strategy beforehand. Considering the usefulness of the technology, it may be adopted in underground mines globally, particularly where fault related deformation pose challenge to roof management. | Underground-mine, fault, roof-collapse, Sub Surface Profiling, roof-management
T04: Deep mining and tunnellingRichard MASETHE (1), Raymond DURRHEIM (2), Musa MANZI (2)1: Sibanyestillwaters, South Africa; 2: University of the Witwatersrand, South AfricaSource mechanisms of mining-induced seismicity at Kloof Gold Mine, South Africa – moment tensor analysis of ML≥1.5 events1683 Mining-induced seismic events in South African deep-level gold mines cause hazardous working conditions, damage infrastructure, delay production and pose a risk to miners. A good understanding of seismic source mechanisms is needed for seismic data to be used efficiently and effectively for mine planning purposes. A comprehensive study of mining-induced seismic events (ML1.5 – 3.3) that caused damage to stopes at Kloof Gold Mine is described. The source mechanisms of 88 events were calculated. All events were located within the central part of the in-mine seismic network, enabling reliable moment tensors to be determined. It was found that approximately equal numbers of events were related to mining-related structures (such as pillars and abutments) and to geological structures (such as faults and dykes). | seismicity, mining-induced, moment tensors, Kloof Gold Mine
T15: Rock and rock mass propertiesHerbert H. EINSTEINMassachusetts Institute of Technology, United States of AmericaPhysical Modeling in Rock Mechanics and Rock Engineering1685 The paper is intended to pay homage to Professor Leopold Müller who was a leading developer and user of physical models. This will be done by reviewing physical models of fundamental material behavior, geologic mechanisms, and especially jointed rock. On this basis complex models of geologic processes and of structures on and in rock masses will be discussed. As will be shown this sequence of topics also corresponds to the history of physical models. Finally, critical aspects, namely the issues of scaling and of obsoleteness because of powerful simulation models will be addressed leading to the outlook as to where physical models can and should be used. | Physical Models, Material, Geology, Jointed Rock, Rock Structures
T01: Challenging rock engineering projectsPrabhat Kumar MANDAL, Arka Jyoti DAS, Ranjan KUMAR, Subhashish TEWARI, Rana BHATTACHARJEE, Awanindra Pratap SINGHCSIR-Central Institute of Mining and Fuel Research, Dhanbad, IndiaDesign of mechanized underground extraction of deep-seated coal seam by continuous miner technology under massive strata and high in-situ stress1686 A mechanised extraction methodology by continuous miner technology is designed for a deep-seated coal seam under massive strata and high in-situ stress conditions by analyzing the stability of rock mass and the rock burst potential through numerical simulation and field investigation. The coal seam having a horizontal-to-vertical in-situ stress ratio of 2.31, is overlaid by the massive sandstone strata and dolerite sill. 3-D numerical simulation is performed to evaluate the stability of rock mass and accumulation of elastic and plastic energy vis-à-vis strain burst index during different stages of the extraction. The energy-based safety factor approach is applied to identify the failed rock mass in the working places to design the support systems to minimise the failure of surrounding rock mass and the rock burst phenomenon. This paper would help the researchers to extract the highly stressed coal seam under massive strata safely and efficiently. | Rock burst, strain energy, massive strata, support design, in-situ stress, side spalling
T13: Numerical methods in rock engineeringFabrício FERNÁNDEZ (1), Eurípedes VARGAS JR. (1), Miguel PAGANIN NETO (2), Elder RIBEIRO (2), Christiano NOGUEIRA (2), Camilla EUZEBIO (2), Joao DELVEAUX (2), Daniel MONTEIRO MACHADO (3), Claus NAVES EIKMEIER (3)1: Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro, Brazil; 2: VALE S.A.; 3: Tetra Tech CoffeySimulation of the run-out and mobilized volume of a 3D rock slope failure using the Material Point Method (MPM)1687 Global and large failures are now the reality of some mines. The risk management process and monitoring system are approaches used to mitigate the problem. However, they cannot avoid the problem when the slope fell or is in a continuum deformation process. Considering slopes in a deformation process, it’s important to know well the limits of the affected area and the mobilized volume for an optimal risk management approach. Runout numerical studies can predict and estimate the limits of the failed material in case of a slope failure. One of the numerical methods suitable for run-out simulation with large deformations is the Material Point Method (MPM). It is a hybrid numerical method that combines the advantages of Lagrangian and Eulerian approaches to simulate continuum mechanics processes with large deformations and displacements. This paper presents the results of a simulation of a large open pit in Brazil using the MPM method. | open pit, slope failure, material point method, large deformations
T16: Underground storage for liquid and gaseous mediaJames Edward John BURTONSHAW, Adriana PALUSZNY, Robert ZIMMERMANImperial College London, United KingdomNumerical Modelling of Induced Seismicity along a Fault during CO2 Injection into a Subsurface Reservoir1688 Injection, storage, and production of fluids in geological media could be a pivotal technology in the energy transition. Injection of fluid into subsurface systems is known to have the potential to induce seismic activity. The present work models induced seismicity during CO2 injection using a three-dimensional finite element-based numerical simulator, the Imperial College Geomechanics Toolkit. Simulations quantify fault slip along a single fault in a five-layer domain of varying permeability. Fluid injection occurs at the left boundary over a period of hundreds to thousands of days, and induced seismicity is monitored during the injection period. Results for varying mesh refinement and properties are compared against a published scenario. The originally two-dimensional model is replicated in 3D, and the same set of material properties are considered, with permeabilities ranging from 10-14 to 10-19 m2. The simulations predict peak slip to within a few centimeters of that of the numerical comparison study. | Underground Fluid Storage, CCS, Induced Seismicity, Fault Slip, Meshing
T17: Rock slope engineeringAmoussou ADOKO, Hayes ANYASODORSchool of Mining and Geosciences, Nazarbayev University, KazakhstanA reliability-based design approach for geotechnical domain modelling in pit slope design1691 The inherent variability of rock mass properties unavoidably leads to imprecisions in open pit geotechnical models, which can increase the likelihood of failures in pit slopes. To overcome this, a reliability-based design approach is advocated to allow for adequate consideration of the design’s uncertainties. In this study, the First Order Reliability Method (FORM) was used to determine the reliability of a pit slope design through a probability of failure. Data from the Bozshakol copper mine located in north Kazakhstan was used in this study. The input data for the FORM analysis were the rock mass properties and the slope design parameters corresponding to selected sectors of the pit. The reliability indices evaluated for each geotechnical domain show good agreement with the slope displacement observations. The results of this study illustrate the importance of a reliability-based design and its capability to be used as basis for improvement of pit slope design. | Reliability analysis, reliability index, probability of failure, open pit slope, geotechnical domain modelling, factor of safety
T13: Numerical methods in rock engineeringWagdi NAIME (1), Roque GARCÍA (2)1: Central University of Venezuela; 2: Andres Bello Catholic UniversityThe accurate knowledge of the joint term for rock mass classification and for the numerical tunnels analysis and its impact on the on the reinforcement’s costs1692 There is an interesting discussion amongst experts about the term discontinuity in the geomechanical rock mass classification for subsurface works applications. This definition, covers the formational planes, like bedding planes and foliation planes, moving fractures and the joints. Using the finite element program, the influence of the rock mass zoning on the stability results and on the dimensions of the required reinforcement were analyzed. The stress relaxation method was considered, defining the characteristic curves for the rock and for the reinforcement. A comparative analysis of the impact on the reinforcement costs is shown when compared with non-zoning model. The proposal is presented to avoid the term discontinuity and to differentiate the real geological structures that affect the rock mass, planes of large continuity, stratification and foliation, from the joints, defined as non-moving fractures whose extension and frequency depend on the changes of the stress state of the rock mass. | discontinuity, joint, geomechanical classification, tunnel analysis
T15: Rock and rock mass propertiesTomas LOKAJICEK (1), Daniela RIMNACOVA (2), Richard PRIKRYL (3), Ali AMINZADEH (1), Matej PETRUZALEK (1)1: Institute of Geology of the Czech Academy of Sciences, Czech Republic; 2: Institute of Rock Structure and Mechanics, Academy of Sciences of the Czech Republic; 3: Faculty of Science, Charles University in Prague, Czech RepublicThermal degradation study of Westerly granite by ultrasonic sounding and mercury porosimetry1693 Westerly granite (WG) is a well-known rock, believed to be isotropic. We studied WG samples heated between 100°C and 800°C, by ultrasonic sounding (US), mercury intrusion porosimetry (MIP). Thermal treatment studies are important for localities like nuclear waste storages, geothermal projects, rocks and earthquake mechanics. All measurements were done at room temperature. It was found that P and S US wave velocity, amplitude, frequency and elastic modulus decreased more than 60% as a result of thermal rock material disintegration due to the increased temperature treatment. Image analyses showed that there is also a preferred orientation of microcracks regardless of their size and thermal treatment level. MIP showed that the pore size distributions vary with different heating temperatures in depending on the thermal WG treatment. | Westerly granite, thermal treatment, ultrasonic sounding, mercury intrusion porosimetry
T06: Geological investigation and characterizationJohannes HORNER (1), Jennifer Andrea BETANCOURT (2)1: recon-struct geologic consulting GmbH, Hallein, Austria; 2: Geologist, Bogotá, ColombiaUnderstanding the geological and geotechnical drill core logging process – key to success1694 The preparation of a consistent ground model in mining and civil construction requires a clear understanding of the geological and geotechnical data collected during the different investigation phases. Drill core logging data may be collected during distinct steps in the drill core logging process. A meaningful interpretation of the drill core logging data is often difficult due to inconsistencies in the logging process and shortcomings in the data management. Such errors and deficiencies can significantly influence the interpretation of the ground conditions. Common sources of error in the drill core logging process include careless drill core handling, inconsistencies in the logging criteria, and the lack of a well-structured data management system. These difficulties can be mitigated or even avoided by identifying the source of error, implementing measures to correct the inconsistencies and by establishing a clear documentation system for the drill core logging process. | diamond drilling, drill core logging, quality control, data management
T10: MonitoringShoji YUKIKO (1), Kikuchi TERUYUKI (2), Koike HITOSHI (3), Shimizu NORIKAZU (4)1: Electric Power Development Co., Ltd., Chigasaki, Japan; 2: J-POWER Design Co., Ltd., Chiyoda, Japan; 3: J-POWER Business Service Corporation, Chuo, Japan; 4: Yamaguchi University, Ube, JapanStrategy and application of slope monitoring over dam basin in regular periods and during emergencies using SAR and GNSS1698 Monitoring the behavior of slopes around the sites of hydroelectric power plants and dam reservoirs over dam basins is important for their stable operation and a reduction in the risks of accidents and disasters. However, since there are numerous slopes widely located over a dam basin, it is generally not feasible to efficiently monitor the behavior of all the slopes over such an extensive area. Satellite technology, SAR and GNSS, will contribute to overcoming this difficulty. In the present paper, a strategy is proposed for slope monitoring over a dam basin in regular periods and during emergencies using SAR and GNSS. Then, practical applications are demonstrated for regularly monitoring the slopes and for detecting unstable slopes during an emergency brought about by an extremely heavy rainfall in Japan. | Monitoring, Slopes, Dam basin, SAR, GNSS
T04: Deep mining and tunnellingXu LI, Guangyao SI, Joung OH, Ismet CANBULATUNSW, AustraliaA modification of the nearest neighborhood triggering mechanism in longwall mining: do seismic events only triggered by its closest neighbors?1700 A common approach in seismology is to use the nearest neighbours method to identify the spatial and temporal relationships between events and select the closest event pairs to identify the triggering cascade. However, in mining engineering, due to the continuous triggering from dynamic mining development as well as the complex geological conditions (e.g., faults), the mining seismic events may not be purely triggered by one prior event, but by a triggering group of a few different events. In this study, we modify the event-event triggering identification approach applied in longwall seismic events. We find that high-energy events can be triggered by previous low-energy events, with clear foreshadowing events. High-energy events can be related to a few low-energy events whose mechanism is based on mining activities. | Longwall mining, Seismicity, rock mechanics
T13: Numerical methods in rock engineeringXu LI, Guangyao SI, Joung OH, Ismet CANBULATUNSW, AustraliaSimulating on the evolution of natural pores and induced microcracks in rock samples: an elastoplastic damage Gurson type model1701 A mechanically acceptable model to explain the evolution of discontinuities inside rock mass and their effect on the entire rock mechanical performance is still required. In this study, an elastoplastic (hardening and softening) damage Gurson-type model is proposed. The behaviour of discontinuities is separated into natural voids and induced microcracks. The behaviour of natural void is further explained by Gurson’s model, considering both the healing mechanism in the initial compaction stage and the damage effect in the crack development stage. The induced microcracks are considered as internal damage, manifested as a damage variable, which directly affects the yielding envelope of porous media (coupled with Gurson’s model) and rock grains (Drucker-Prager law in the effective stress domain). The proposed model shows great consistency with laboratory observations. | microcracking, rock mechanics, constitutive model, Gurson’s model
T05: Digitalization & AutomatisationZizhuo XIANG, Zexin YU, Joung OH, Guangyao SI, Ismet CANBULATUniversity of New South Wales, AustraliaA machine learning model to estimate in-situ rock strength from borehole geophysical logs1702 This paper proposes an artificial neural network (ANN) model, which aims to improve the estimation accuracy of in-situ rock uniaxial compressive strength (UCS) for the Australian mining industry. The model utilises borehole geophysical logs (i.e., sonic, neutron, gamma and porosity logs) and rock density as inputs. A dataset of 274 samples from two mine sites in Australia is applied for the training, testing and validation of the model. Compared with the conventional sonic velocity model, the mean absolute percentage error of the predictions improves from 34.3% to 19.8% and the root mean squared error is reduced by over 4.6 MPa. In addition, it is also obtained that the accuracy of the model varies depending on the lithologies and mine locations. The proposed model is expected to provide more accurate rock strength estimations and be beneficial for further geotechnical analysis, such as estimating in-situ stresses based on borehole breakout. | Uniaxial compression strength, In-situ rock strength estimation, Borehole geophysical logs, Artificial neural network
T11: NATM versus TBMHan-Young JEONG (1), Mun-Gyu KIM (1), Yun-Joo NAM (1), Min-Gi CHO (1), Jung-Woo CHO (1), Sung-Bo SHIM (2)1: KITECH (Korea Institute of Industrial Technology), Republic of Korea (South Korea); 2: Kyungpook National University, Daegu, Republic of KoreaCompression test of TBM thrust jack for validation of bucking strength under inclined loading condition1703 This paper studies a consecutive excavation technique to enhance the shield TBM advance rate. Helical type segments are considered for one solution for the continuous excavation of shield TBM. When using helical segments, the thrust jacks compress on the inclined side wall of the segments. The inclined contact can induce the side force and bending moment of the hydraulic cylinder, which can arouse oil leak or plastic deformation of rod and cylinder parts. The study examined the buckling reliability of thrust jack against to the compressive force on the inclined surface of helical segment. A numerical simulation was conducted for analyzing the structural stability. The reliability testing code was established and the testing specimen of jack and loading jigs were manufactured for the compression test of the jack. After the compression test was conducted, the testing results are summarized for validation. | Shield TBM, Thrust jack, Helical segment, Inclined surface, Compression test
T05: Digitalization & AutomatisationTae Young KO, Ju-Pyo HONGDepartment of Energy and Resources Engineering, Kangwon National University, Chuncheon, KoreaComparative Analysis of CAI Estimation using Symbolic Regression and Machine Learning Approaches1705 The abrasiveness of rocks being excavated is a major challenge in TBM tunneling, as it affects the performance and durability of cutting tools. The Cerchar abrasivity Index (CAI) is a widely used method to assess rock abrasiveness and predict tool wear and cutter life in TBM tunneling. The CAI can be estimated from rock properties, such as compressive strength, tensile strength, and petrographic factors. A novel approach using symbolic regression was proposed to predict CAI. Symbolic regression can generate accurate and interpretable mathematical equations to capture the relationship between inputs and outputs. The proposed approach was compared to traditional machine-learning-based regression models using a dataset obtained from published articles and geotechnical data reports. Various machine-learning-based regression methods were also used to forecast the CAI, and their performances were compared. The proposed symbolic regression-based CAI prediction model has the potential to improve the performance of models for predicting rock abrasivity. | Cerchar Abrasivity Index, Wear, Symbolic Regression, Machine Learning
T12: New developments in rock supportJemishkumar Vijaykumar MODI (1,2), Debasis DEB (2), Rakesh KUMAR (2)1: Government Engineering College Palanpur; 2: Indian Institute of Technology KharagpurExperimental Investigations of Instrumented Fully Grouted Rock Bolts under Pull Load1709 Rebar-type rock bolts of 22 mm and a length of 600 mm are instrumented with four resistance strain gauges along the length. A total of 450 mm bolt lengths is embedded with resin grouted inside a cement mortar cast cylindrical sample of diameter 250 mm. Strain gauges are placed on the surface of the rod at four locations. The diameter of the hole is varied as 32 mm, 36 mm, and 42 mm. The bolt is embedded cement mortar samples are placed in a pull-testing machine and firmly fixed on the frame by tie-rods. The rod is pulled with three different loading groups of rates. This paper analyzes load-deformation relationship curves for different hole diameters of pulling to observe the variation in peak bond strength and stiffness. The tensile strains obtained at four locations are validated with an analytical equation are in the paper. | Fully grouted rock-bolt, pull-out tests, bond strength, bond stiffness, axial strain
T06: Geological investigation and characterizationYuanyuan WEI, Hui WUPeking University, People's Republic of ChinaInvestigation of the effect of matrix on tracer transport processes in subsurface fractured reservoirs1710 Tracer testing is a commonly used method to characterize flow and transport in subsurface fractured reservoirs. The interpretation of tracer recovery data generally requires numerous forward simulations of tracer transport in the underlying fracture and matrix. Previous studies have attempted to alleviate the associated computational burden by neglecting the matrix, but the impact of such a simplification remains unclear. This study systematically investigates the effects of matrix on tracer transport processes under various fracture/matrix parameters and tracer injection conditions through an analytical solution. Based on the results, we discuss the situations in which matrix has minimal effect on tracer transport and can be ignored during inversion/data assimilation. A dimensionless number that integrates fracture/matrix parameters and injection parameters is proposed to estimate matrix effect on tracer transport. The dimensionless number offers an easy yet practical way to quantify matrix effect, providing informative guidance for model development in tracer data interpretation. | Tracer transport, fractured reservoir, matrix effect, tracer injection condition, dimensionless number
T17: Rock slope engineeringSom NATH (1,2), Ashok Kumar SINGH (3), Harsh Kumar VERMA (2), Nachiketa RAI (1)1: Indian Institute of Technology Roorkee, India; 2: CSIR-Central Institute of Mining and Fuel Research, Regional Research Centre Roorkee (UK) India; 3: CSIR-Central Institute of Mining and Fuel Research, Regional Research Centre Bilaspur (CG) IndiaEffect of blast damage zones on the stability of a Himalayan highway cut-slope ₋ continuum modelling approach1712 Hoek & Brown introduced the disturbance factor, "D," to their failure criteria in order to account for the critical effect of blast-induced damage zone in the assessment of the rock mass parameters. Considering the vital effect of blast damage extent on the surficial stability of jointed cut slopes, the present study examines the stability behavior of a jointed cut slope that had been excavated through rough blasting practice along NH-5 in dynamic Himalayan conditions in Himachal Pradesh, India. The effect of the blast damage zone on the stability behavior has been investigated through continuum-based Finite Element modeling. A parametric study has been done by assigning different damage factor ‘D’ to the damage zone of the rock slope. The results demonstrate the variability in safety factors of jointed cut-slopes in relation to the extent and degree of blast-induced rock mass damage of the disturbance zones. | Blast-induced damage zone, Highway slopes, Safety factor, Continuum modelling, Himalaya
T14: Petroleum engineering and carbon sequestrationPankaj RAWAT, Narendra Kumar SAMADHIYAIndian Institute of Technology Roorkee, IndiaLaboratory hydraulic fracturing experiments on thermally treated tight sandstone samples under step up incremental loading1715 This paper aims to investigate the effect of thermal treatment on tight sandstone samples during the hydraulic fracturing process. The sandstone samples were preheated at different temperatures and cooled at the same rate (1 ᵒC / min). Step-up incremental loading opted for all hydraulic fracturing experiments. SEM investigations were done on thin sections of fractured samples to find the fractal dimension and tortuosity. After 300 ᵒC, the samples hydro fractured at higher temperatures and showed lower fractal dimensions than those at lower temperatures. The effect of the heat treatment was also observed in the breakdown pressures as they reduced with the increased temperature. Due to the thermal effects, it was also found that the crack tortuosity increased with an increase in temperature. After 300 ᵒC, the degree of micro cracks and the complexity of the fracture growth network increases. | Step up incremental loading, fractal dimension, tortuosity, SEM (Scanning electron microscope) images
T17: Rock slope engineeringCheng-Han LIN, Ming-Lang LINDepartment of Civil Engineering, National Taiwan University, TaiwanActivity and kinematic behaviors of gravitational slope deformation in the slate belt of Taiwan1718 In the slate belt of Taiwan, there have been numerous studies exploring landslide activity or gravitational slope deformation (GSD) since the 2009 Typhoon Morakot. However, studies evaluating the relationship between present-day activity and long-term deformation have been infrequent due to a lack of multi-temporal monitoring data and analysis tools. The Chingjing region, which contains many GSDs and famous rockslides, is one such region that requires further investigation in this context. This study aims to interpret the evolution of slate slope deformation from long-term kinematics to short-term activity. We first observe the surficial displacement rate during the period of 2018-2020 using multi-temporal InSAR analysis. The radar satellite-based surface observation was then supplemented with numerical analysis based on the distinct element method to characterize the sub-surface gravity-driven slope movement. Our results help explain the evolution of gravitational slope deformation in slate slopes and better assess rockslide hazards transferred from GSD. | Gravitational slope deformation, slate slope, multi-temporal InSAR analysis, distinct element modeling
T11: NATM versus TBMMun-Gyu KIM (1), Han-Young JEONG (1), Joo-Young OH (1), Jung-Woo CHO (1), Sang-Hwa YU (2), Ho-Young JEONG (3)1: KITECH (Korea Institute of Industrial Technology), Republic of Korea; 2: Hochang Engineering Co., Republic of Korea; 3: Pukyong University, Busan, Republic of KoreaPerformance validation of rock cutting-splitting method by scaled model tests and rock slope excavation1719 A cutting-splitting method is developed as a mechanized excavation for rock slope and tunnelling. The technique has two procedures. The first step is the rock cutting as designed dimensions (i.e. depth, spacing, width). The second is the rock splitting process by inserting chisel into the cutting slot to split out a rock block. For propagation of tensile crack on the bottom of rock, a sufficient indenting force should be loaded on the cutting slot. An analytic solution was proposed to estimate the indentation force. Numerical analyses were conducted to analyze the tensile fracturing process during the splitting process. A series of scaled model tests were designed and conducted to evaluate the advantageous geometry for the method. Finally, in-situ excavation tests were carried out for a rock slope. The results were compared to the previous method (i.e., drilling-splitting method). It is concluded that the developing method can improve the cutting rate of hard rock. | non-vibrating, cutting-splitting, numerical analysis, scaled model test, rock slope excavation
T04: Deep mining and tunnellingJoel CHIWARA (1), Ioannis VAZAIOS (2), Chrysothemis PARASKEVOPOULOU (1)1: University of Leeds, United Kingdom; 2: Ove Arup & Partners Ltd, London, United KingdomThe influence of brittle failure and its impact on face stability in high-stress tunnelling conditions1720 In deep hard rock environments under high-stress conditions, rockmasses behave in a brittle manner resulting in spalling and strain bursting. This paper examines the occurrence of brittle failure and its impact on face stability. Generalised Hoek-Brown failure criterion modified after the Damage Initiation and Spalling Limit (DISL) approach is adopted in 2D and 3D numerical models to capture the mechanical response of brittle rocks in underground excavations. Unsupported circular tunnel models are used to investigate brittle failure at the tunnel face. Excavation induced stress and deformation results show that under anisotropic in-situ stress conditions, models become unstable, and relaxation rapidly increases within 3 m behind the tunnel face, while within a distance of 0.85 times the tunnel radius, the tunnel relaxes 85% to 95%. This demonstrates the rapid loss of confinement in hard rock masses within the face vicinity which yields instabilities in the tunnel. | brittle failure, high-stress, tunnel face stability, strain bursting, hard rock tunnelling, deep mining
T18: Early Career Forum (Young Researchers)Gustavo André PANEIRO (1), Ignacio PÉREZ-REY (2), Xian ESTÉVEZ-VENTOSA (2), Leandro R. ALEJANO (2)1: DER/CERENA, Técnico Lisboa, ULisboa, Portugal; 2: CINTECX, Grupo de Xestión Segura e Sostible de Recursos Minerais, Universidade de Vigo, SpainExperimental assessment of high temperature-induced changes on frictional behavior of planar rock joints1722 It is accepted that heat waves, whose occurrence have been increasing throughout the last decades in the Iberian Peninsula, associated with climate change, are one of the main hazards linked to the occurrence of wildfires and the increase of fire risk in the open-pit mining industry. To the best of our knowledge, studies that relate the effect of temperature (produced by a fire) on jointed rock masses are scarce. This paper considers the development of benchmark work for the determination of the basic friction angle on suitably prepared saw-cut planar granitic joints, some of them subjected to thermal ageing, and by means of an automatic tilt test apparatus for both reference (no thermal ageing) and thermally aged samples. The results show the influence of high temperatures on the frictional behavior of rock joints, particularly relevant for the stability assessment after a fire or wildfire occurrence near outcrops and excavations. | Rock mass, joint, thermal ageing, friction angle, tilt test
T05: Digitalization & AutomatisationMateusz JANISZEWSKI, Lauri UOTINEN, Masoud TORKAN, Mikael RINNEAalto University, FinlandVirtual learning environments for rock engineering education and training - a guideline for development, examples, and lessons learned1723 This paper presents the research and educational development activity at Aalto University in creating virtual learning environments for rock engineering education. Virtual learning environments are increasingly recognized as tools to improve engineering education, but their creation requires specialized knowledge of 3D scanning, computer graphics, and game development. The paper discusses a method for creating 3D models of real environments using photogrammetry, along with hardware and software options. The models are then integrated into virtual learning systems built using game engines. Two case examples focusing on digitizing sites for virtual rock mass mapping are presented, and the outcomes and lessons learned are discussed. The paper concludes that accurate and photorealistic virtual learning environments can be developed to enhance rock engineering education and training. This has implications for the future development of virtual learning environments in engineering education and highlights the potential for using extended reality technology to communicate complex spatial data. | virtual reality, engineering education, photogrammetry, virtual learning environment
T08: Hydropower projects and damsFrancisco RÍOS BAYONA (1), Fredrik JOHANSSON (2), Diego MAS IVARS (2,3), Carl-Oscar NILSSON (4)1: Typsa AB, Department of Civil Engineering, Stockholm, Sweden; 2: KTH Royal Institute of Technology, Department of Civil and Architectural Engineering, Stockholm, Sweden; 3: SKB Swedish Nuclear Fuel and Waste Management Co, Solna, Sweden; 4: Uniper – Sydkraft Hydropower AB, Östersund, SwedenA possible way forward to predict the peak shear strength of a natural, unfilled rock joint under concrete dams based on field data1724 The prediction of a rock joint’s peak shear strength becomes complex when its joint surfaces are not fully accessible, such as the rock foundation under an existing concrete dam. This paper presents a case study with the application of a newly developed methodology that uses objective observations of the 3D roughness and joint aperture from drill cores to predict the peak shear strength of large natural, unfilled rock joints. Eight rock joint samples obtained after core-drilling an existing rock joint adjacent to the foundation of Storfinnforsen dam in Sweden were used. The main benefit of this approach is that it enables the prediction of both the mean value and the statistical uncertainty of the peak shear strength under conditions of difficult access. This information may be of importance in order to assess the safety in the foundation of an existing concrete dam. | Rock joints, peak shear strength, concrete dams, field observations, drill cores
T09: Long term behaviour of underground structuresChrysothemis PARASKEVOPOULOU (1), James INNOCENTE (2), Mark MCDONALD (2), Mark DIEDERICHS (2)1: University of Leeds, United Kingdom; 2: Queen's University, CanadaTime-dependency and long-term strength of rocks in brittle underground environments – from the lab results to numerical continuum analysis1725 There has been a wide effort to develop constitutive models to aid prudent engineers or scientists in understanding materials' behaviour in rock mechanics. Hoewever, there is still a lot of work to be done when considering time-dependent behaviour that can lead to instabilities and progressive failures which cannot be captures when considered the commonly used constitutive models, usually static. This paper aims to provide more insight into understanding time-dependent behaviour at both the laboratory and excavation scale. Building on the findings this study develops in-depth understanding on capturing the time-dependent behaviour in brittle rock materials proposing a new approach to be adopted when simulating numerically this behaviour highlighting key considerations both at the laboratory and tunnel scale. | long-term behaviour, time-dependency, time-to-failure, creep, strength degradation
T14: Petroleum engineering and carbon sequestrationCecilia LASKOWSKI (1,2), Diego MANZANAL (2), Mauro MUÑIZ-MENÉNDEZ (3), Sandra ORLANDI (1), José ALLARD (1)1: Universidad Nacional de la Patagonia San Juan Bosco, Comodoro Rivadavia, Argentina; 2: Universidad Politécnica de Madrid, Madrid, Spain; 3: Laboratorio de Geotecnia, CEDEX, Madrid, SpainCarbon dioxide impact on the mechanical properties of a sandstone from San Jorge Gulf Basin (Argentina)1728 During the last few years, there has been an increase in awareness related to global warming. In this context, carbon capture and storage comes into play, intending to reduce the emission of greenhouse gases. This research focuses on reservoir rocks from the San Jorge Gulf Basin (Argentina). To analyze the feasibility of storing CO2 in the reservoir layer, this research studies the evolution of the rock’s porosity and mechanical properties, using samples obtained from outcrop. With this aim, a series of tests such as Mercury Intrusion Porosimetry, X-Ray Fluorescence, and Uniaxial Compressive tests were performed over both unaltered and CO2-altered specimens. Preliminary results show a variable affectation of the porosity, mainly in the carbon dioxide contact zone. Carbonated samples also seem to present modifications in their mechanical properties. | carbon dioxide, CO2 geological storage, sandstone, mechanical characterization
T16: Underground storage for liquid and gaseous mediaStefan ZELZER, Thomas GEISLER, Thomas MARCHERInstitute of Rock Mechanics and Tunnelling, Graz University of Technology, AustriaA guidance for the optimal site location of Cavern Thermal Energy Storage (CTES)1731 The production of energy using CO2-neutral methods faces an additional challenge to conserve surplus energy over longer periods of time and to be able to use it when required. One possibility for meeting this challenge is the use of CTES (Cavern Thermal Energy Storage). These CTES store surplus heat in the form of hot water and preserve it for a desired period. Many cities feature the necessary rock formations to build and operate these CTES. For this reason, a guideline has been elaborated that combines the most important geotechnical parameters with the local rock mass conditions. In addition, this guideline pays special attention to the geometric dimensions since these have a significant influence on the stratification of water within the storage medium. It is possible to make a first selection of possible sites and to investigate them in more detail with this geotechnical guidance. | Thermal Energy Storage, Underground Heat Storage, Site Selection Criteria, Thermal Stratification, Suitable Rock Mass
T15: Rock and rock mass propertiesDaniela ŘIMNÁČOVÁ (1), Dominik VÖRÖŠ (1), Vendula NATHEROVÁ (1,2), Richard PŘIKRYL (2), Tomáš LOKAJÍČEK (3)1: Institute of Rock Structure and Mechanics of the Czech Academy of Sciences, Czech Republic; 2: Institute of Geochemistry, Faculty of Science, Charles University in Prague, Czech Republic; 3: Institute of Geology of the Czech Academy of Sciences, Czech RepublicPorosity of source rocks eligible for interaction with gases and liquids1732 The extent of the porosity of different source rocks may vary with their composition, weathering of the bedrock etc. To determine the further use of source rocks, it is necessary to understand and describe their physicochemical properties. Complex textural analyses of source rocks with variable amounts of organic matter were carried out using N2 and CO2 sorption, scanning electron microscopy and mercury intrusion porosimetry. The total adsorption of CO2 ranged from 0.03 to 1.5 mmol/g. The porosity and the pore size distribution varied according to the origin of the studied samples. The porosity ranged from 0.2% to 21%. Lower porosity values indicated a connection with gas capturing. Higher porosity values can be explained by the presence of macropores and larger pores, serving mainly for the migration of gases and liquids. Monitoring of sorption properties can provide a scientific basis for the safe utilization of reservoirs and rock layers. | Rocks, porosity, gas adsorption, textural parameters
T13: Numerical methods in rock engineeringYasuhisa AONO, Tetsuo OKUNOShimizu Corporation, JapanData Assimilation for Prediction of Surrounding Rock Mass Behavior during Underground Structure Construction Phases1733 To ensure safety during the construction of underground structures, the present and future conditions of rock and tunnel supports, such as displacements, stresses, and plastic regions, must be estimated and predicted by appropriate measurements and numerical simulations. However, there are many uncertainties, such as geological structures, mechanical properties of rocks, and initial and boundary conditions, which considerably complicate numerical modeling. To solve this problem, this study develops a numerical analysis method using a data assimilation (DA) technique that updates the numerical model based on the measured data during construction. Numerical experiments were conducted to evaluate the effectiveness of the proposed method. DA analyses were performed using the displacements obtained from the simulated measurement data. As a result, DA updated the physical properties of the elasto-plastic model and improved the prediction performance of the displacements and plastic region of the surrounding rock mass during tunnel construction. | Ensemble-based data assimilation, Underground structures, Numerical analysis, Strain softening
T15: Rock and rock mass propertiesRahul Rooplal KATRE, Nikhil Ninad SIRDESAI, Sandeep PANCHALDepartment of Mining Engineering, Visvesvaraya National Institute of Technology, Nagpur, Maharashtra, IndiaInfluence of grain-size on damage in thermally treated granites- A Review and Novel quantification techniques1735 Response of thermally treated granites are analyzed by several authors for processes like geothermal energy extraction, underground disposal nuclear waste, energy storage and structures exposed to fires. Although the conducted research helps to increase our understanding on the granites, quantification of thermal rock damage requires further studies which consequently alter the physico- mechanical response. So far, thermal damage is determined as a function of elastic modulus. However, an accurate determination of elastic modulus requires specialized laboratory facilities. When the treated granites (600°C) are allowed to cool in ambient temperature, the density decreases by 7.7%, 2.2% and 3.67% for coarse, medium and fine-grained granite, respectively. This reduction is primarily caused by the volumetric expansion of the mineral grains as seen by internal micro-cracking. In this study, the authors have quantified damage as a function of rock properties other than elastic modulus to appreciate the influence of temperature on varying grain-size. | Granite, Mineralogy, Morphology, Temperature, Damage
T13: Numerical methods in rock engineeringTemenuga GEORGIEVA (1,2), Fanny DESCAMPS (1), George AJDANLIJSKY (3), Sara VANDYCKE (1), Nicolas GONZE (1), Jean-Pierre TSHIBANGU (1)1: University of Mons, Belgium; 2: Euridice, Belgium; 3: Bulgarian Academy of Sciences, BulgariaInfluence of deep coal mines on the stability of shallow cavities1736 Wallonia and Hauts-de-France regions encounter complex developments of multi-level mining cavities that may affect the stability of shallower ones. This work focusses on an abandoned room-and-pillar quarry that extracted phosphatic chalk. On the same site, coal was mined out at depths from 200 to 750 m. To evaluate the influence of deep coal mines on the stability of shallow cavities, the geometry of created voids was modelled, integrating the mining sequence. In addition, detailed topographic and structural surveys of the chalk quarry were completed by rock mass quality assessment. Then a finite element geomechanical model combining the room-and-pillar quarry and the longwall mining was created. Specific vertical cross sections were investigated. The model revealed the progressive influence of coal mining on the room-and-pillar quarry as the surface mined out increased. These large models finally provide boundary conditions for local models in which the influence of specific parameters can be investigated. | post mining, stability analysis, finite element model, room-and-pillar, longwall mining
T05: Digitalization & AutomatisationHannah SALZGEBER, Larissa SCHNEIDERBAUER, Kathrin GLAB, Matthias FLORAUniversity of Innsbruck, iBT, AustriaStudy on comparing current software for parametric modelling in Tunnel Information Modelling1739 The Tunnel Information Modelling (TIM) method has presented the tunnelling industry with certain modelling challenges. Tunnel structures are characterised by the arrangement of recurring components along an alignment and the therefore resulting lengthy and repetitive modelling task requires automation through parametric design. This paper presents an evaluation of currently used software solutions for TIM, which are able to implement parametric modelling via extensions or scripting. The comparison includes aspects of geometrical modelling, integration of alphanumerical information into model components and drawing derivation. The resulting table gives a consolidated overview of the findings and caters to anybody who is currently looking at the implementation of a viable software options for the application of TIM. | BIM, TIM, parametric modelling, digitalisation, tunnelling
T05: Digitalization & AutomatisationInes MASSIMO-KAISER (1), Hans EXENBERGER (1), Hannah SALZGEBER (1), Hannah WERKGARNER (1), Richard LOIDL (2), Matthias FLORA (1)1: Universität Innsbruck, Austria; 2: ASFINAG Bau Management GmbHFrom prognosis Ground Model to Tender Model and Tunnel Construction Framework Plan with Tunnel Information Modelling1740 This article presents a concept for a digital ground model usable throughout all project phases and visualizes causalities between geological conditions and the tunnel structure. Specifically, a dynamic modeling approach is introduced to represent the geological conditions from design to construction. Three process phases are dealt with: (i) a preliminary phase defining the model area, (ii) the geological prognoses, including parameterization and schematization along the alignment as a base for further planning steps, and (iii) the creation of a cumulative tunnel construction model. A schematic, parameterized, small-scale tunnel excavation element model is the basis for a dynamic adaptation of geology. In addition, detailed predictions modeled along the alignment are introduced to represent the predicted geology in higher detail, adjustable in the event of changes, and thus represent the current geological information in the construction area. These models form the basis for a tender model and a digital tunnel construction framework plan. | TIM, framework plan, ground model, design process
T06: Geological investigation and characterizationThomas DICKMANN (1), Jozsef HECHT-MÉNDEZ (1), Dirk KRUEGER (1), Christoph SINKOVEC (2), Christian SCHÖNLECHNER (2)1: Amberg Technologies AG, Switzerland; 2: Jäger Bau GmbH, Bludenz, AustriaRapid seismic data acquisition in a TBM road tunnel excavation with segmental lining1741 Dedicated tunnel reflection seismic is a reliable geological exploration tool. In this method, 24 boreholes are prepared along a tunnel wall, which serve as seismic sources. In four additional boreholes, tri-axial seismic sensors are installed. By recording P- and S-waves propagating through the rock mass, seismic velocities are obtained, and an estimation of rock mechanical properties is possible. Changes in these properties allow for better understanding of the rock mass condition ahead of the face and timely identification of hazardous zones. Experiences on using reflection seismic during the construction of a double-shield TBM road tunnel in Switzerland are presented. Data acquisition was carried out by the tunnel contractor and data processing and evaluation by specialists in tunnel seismic. With 17 seismic measurements, a forecast of the rock mass was made over a length of 2,200 meters. Furthermore, the disturbance-free seismic data acquisition could be tested using an innovative next-generation hardware. | in-tunnel reflection seismic, geological forecast, rock mechanical parameters, site characterization
T17: Rock slope engineeringMaria Teresa CARRIERO (1), Cesare COMINA (2), Anna Maria FERRERO (2), Maria Rita MIGLIAZZA (1), Battista TABONI (2), Gessica UMILI (2), Federico VAGNON (1), Sergio Carmelo VINCIGUERRA (2)1: Polytechnic of Turin, Turin, Italy; 2: University of Turin, Turin, ItalyGeotechnical and geophysical investigation of a rock mass for the design check of an ornamental stone quarry1743 The design of an open-pit quarry must continuously adapt to the real conditions of the excavation faces, to meet safety requirements and maximize the effectiveness of the operational process. The case study of an ornamental stone quarry characterized by great value and challenging excavation geometry is analyzed in this study. The exploited rock mass is characterized by a non-ubiquitous discontinuity distribution due to the presence of highly fractured bands, mainly parallel to the excavation faces. The discontinuity network needs to be analyzed to forecast the rock mass mechanical behavior during excavation. In this regard, the integration of geotechnical and geophysical surveys allows the rock mass to be studied from the surface to a considerable depth. Trace mapping on scaled digital images was combined with traditional geomechanical methods and GPR surveys, executed on the excavation faces, to assess the variability of discontinuity spacing and to characterize the fractured bands. | open-pit quarry, spacing, digital images, GPR, fracture band
T05: Digitalization & AutomatisationSarp SAYDAM (2,1), Chengpei XU (1), Binghao LI (1), Birgul TOPAL (1), Serkan SAYDAM (1)1: MERE, Faculty of Engineering, University of New South Wales, Australia; 2: DYWIDAG-Systems International Pty Limited, AustraliaFeature Sampling and Balancing for Detecting Rock Bolts from the LiDAR Point Clouds1744 Rock bolts play a crucial role in enhancing the stability of tunnel structures. However, designing bolt detection methods from LiDAR point clouds often faces the challenge of data imbalance. Despite this, the state-of-the-art deep learning-based detection methods adopt uniform sampling strategy for both bolt and background points without considering their unequal distribution, leading to a substantial loss of bolt features and overabundance of noise points. We propose a novel bolt feature sampling and grouping strategy by integrating principal component and surface curvature analysis to balance the noise background points and the bolt points. The balanced point features are fed into a newly designed deep neural network with a weighted loss function to accurately detect the position of rock bolts. The proposed method achieves state-of-the-art results on the Civil Tunnel dataset and Mining Tunnel dataset, outperforming the state-of-the-art 3D deep learning-based detection methods with uniform sampling strategy. | Rock bolt detection, point cloud, LiDAR, neural network
T09: Long term behaviour of underground structuresM. Cristina SACEANU (1), Adriana PALUSZNY (1), Robert W. ZIMMERMAN (1), Diego MAS IVARS (2,3)1: Imperial College London, London, SW7 2AZ, United Kingdom; 2: Swedish Nuclear Fuel and Waste Management Company (SKB), Solna, Sweden; 3: Royal Institute of Technology (KTH), Stockholm, SwedenEvolution of spalling-inducing fractures around a deep geological repository for nuclear waste during glaciations and their effect on the long-term repository stability1746 This paper studies the potential impact of glaciations on the deposition boreholes of the future deep geological repository for nuclear waste at Forsmark, Sweden. A multiple-borehole numerical model is considered, in which fracture growth leading to spalling is simulated in three-dimensions, using the Imperial College Geomechanics Toolkit, a finite element-based discrete fracture growth simulator. Fractures initiate in tension due to in situ stress redistribution after drilling, and grow based on stress intensity factors computed at fracture tips. Glaciation is modelled through its effect on the horizontal stresses determined by ice-crust-mantle simulations, and the vertical stress is determined by the weight of the overlying ice sheet. Numerical results indicate that changes in the in situ stresses influence nucleation and growth patterns, increasing the extent of the damaged rock around the deposition boreholes during the glacial cycle. | deep geological disposal, nuclear waste, spalling, numerical modelling, glaciations
T15: Rock and rock mass propertiesAndreas MAYER (1), Franz REITER (2), Andreas FREUDENTHALER (3), Miroslav MARENCE (4)1: Büro für Geologie und Hydrogeologie ZT GMBH, Austria; 2: ÖBB Infrastruktur AG; 3: AFRY Austria GMBH; 4: AFRY Austria GMBHThe Tauernmoos pressure tunnel: a multidisciplinary approach to verify and ensure design rock mass conditions during construction1747 A 1.6 km long headrace tunnel has been constructed for the Tauernmoos hydro power plant. For the dimensioning of the tunnel lining, a minimum elastic modulus requirement of 15 GPa for the surrounding rock mass was formulated. The objective for the geological documentation was therefore the identification of zones with an elastic modulus below the required minimum. This was achieved by detailed mapping of the embrasure as well as by correlating the UCS, determined by Schmidt hammer, with the elastic modulus. For parts of the headrace tunnel, additional dynamic elastic moduli were established using refraction seismic surveying. That way, critical areas in terms of deformational behavior along the headrace tunnel could be determined. A consolidation grouting campaign with primary and secondary injection rings was carried out to improve the elastic moduli. The success of this measures was confirmed with a post-grouting seismic survey. | headrace tunnel, elastic modulus, Schmidt hammer, refraction seismic, grouting
T15: Rock and rock mass propertiesYulong SHAO, Jineon KIM, Jae-Joon SONGSeoul national university, Korea, Republic of (South Korea)4D imaging of crack evolution and failure mode in 3DP rock-like samples under uniaxial compression by using in-situ micro-ct technology1748 Previous studies have investigated static cracks and pores before and after compressive tests of 3D-printed (3DP) rock with limitations in describing real-time cracking and damage evolution during compression. In this study, compression tests were conducted on 3DP gypsum rocks using an in-situ micro-computed tomography (micro-CT) system to obtain 2D CT images during compression. Through 3D reconstruction of 2D CT images, crack propagation and pore evolution of 3DP gypsum rocks could be illustrated from a 3D stereoscopic perspective and quantitatively analyzed. Results indicated that multiple tensile cracks propagated along the axial direction during compression. Initially, the volume of 3DP gypsum rocks decreased owing to pore closure during the compaction stage in which cracks were yet to be initiated. As the external stress exceeded the bearing capacity of 3DP gypsum rocks, the crack volume increased first marginally and then rapidly as cracks initiated and further developed with the increased stress. | 3DP gypsum rocks, in-situ micro-CT, 3D reconstruction, crack propagation, pore evolution
T15: Rock and rock mass propertiesMinoru SATO (1), Takato TAKEMURA (2), Daisuke ASAHINA (3)1: Central Research Institute of Electric Power Industry, Japan; 2: Geomechanics Lab., Department of Earth and Environmental Sciences, Nihon University; 3: Geological Survey of Japan, AISTMechanical properties of 3D printed sandstone analogue with different binder rates1749 The mechanical properties of natural rocks obtained by laboratory tests vary considerably with rock anisotropy and heterogeneity by the formation process, and measurement accuracy of the equipment. However, it is difficult to evaluate these effects separately using natural rocks. Using three-dimensional (3D)-printed analogue minimizes the variations in the mechanical properties of rocks. In this study, the mechanical properties of 3D-printed sandstone analogues with different binder rates and jacketing conditions are examined at conventional triaxial compression (CTC) and true triaxial compression (TTC) stress conditions. This study demonstrates that the peak strength is slightly different for the same binder-sand weight rate samples; however, the deformation behavior observed from the shape of the stress–strain curve is similar. The mechanical properties and deformation behavior of the 3D-printed sandstone analogues are similar to those of natural sedimentary rocks under CTC and TTC testing conditions. | 3D printing, sandstone, mechanical properties, true triaxial test, triaxial test, P-wave velocity
T10: MonitoringJune Ho PARK (1), Jin Seop KIM (2), Chang Ho HONG (2), Ji Won KIM (2), Tae Hyuk KWON (1)1: Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea; 2: Korea Atomic Energy Research Institute, Yuseong-gu, Daejeon, Republic of KoreaLow-frequency acoustic emission characteristics from meter-scale fracturing of rock-like brittle materials1751 The acoustic emission (AE) method as a passive non-destructive monitoring technique is proposed for real-time monitoring of mechanical degradation in underground structures, such as deep geological disposal of high-level nuclear waste (HLW). This study investigates the low-frequency characteristics of AE signals emitted during fracturing of meter-scale concrete specimens. For comparison, uniaxial compression tests (UCT) and Goodman jack (GJ) tests in a 1.3 m-long concrete block were conducted while acquiring the AE signals using low-frequency AE sensors. The results showed that a sharp increase in AE energy emission occurred at ~60% and ~80% of the yield stresses in the UCT and GJ tests, respectively. High frequency AE signals were captured more as the tress increased in the GJ tests, which was in contrast to the UCT tests. The study presents unique experimental data with low-frequency AE sensors under different loading conditions, which provides insights into the field-scale AE monitoring practices. | Acoustic emission, low-frequency sensor, meter-scale, concrete, Goodman jack test
T01: Challenging rock engineering projectsShikang QIN (1), Chen XU (2,3), Xichen LI (4), Yabin HUANG (5), Qing YAO (2)1: College of Civil Engineering, Tongji University, Shanghai, China; 2: Institute of Rock Mechanics, Ningbo University, People's Republic of China; 3: Ningbo Key Laboratory of Energy Geostructure, Ningbo, China; 4: Shanghai Giant Energy Technology Co., Ltd., Shanghai, China; 5: The 4th Construction Co. Ltd. of China 15th Corporation, People's Republic of ChinaCollapse mechanism and treatment technology of large-span soft rock highway tunnel1753 Tunnel collapse seriously affects the security of the constructers and delays the engineering schedule. Based on the Liangwangshan Tunnel project located in western China, the collapse mechanism of large-span soft rock tunnel under loose load was revealed by theoretical calculation, field measurement and numerical simulation. The low strength-stress ratio of the unconsolidated fragment rock mass leads to a very high loose pressure. The measured stresses of the arch have exceeded its strength, which indicates that the arch is less secure. The FEM results show that I18 steel arch is incapable of resisting ground pressure in this project. Besides, a segmented and graded treatment technique was proposed to deal with tunnel collapse, and the tunnel deformation was successfully controlled. The monitoring data showed that the tunnel was stable after treatment, which shows that the segmented and graded treatment technique was successful and effective. | large-span tunnel, soft rock tunnel, in-situ monitoring, collapse mechanism
T13: Numerical methods in rock engineeringTuan Anh BUI (1), Giuseppe CAMMARATA (1), Varun Choudary KANCHARLA (1), Ronald BRINKGREVE (2), Sandro BRASILE (1)1: Seequent, The Bentley Subsurface Company, The Netherlands; 2: Delft University of Technology, The NetherlandsOn advanced numerical techniques for the modeling of bolt reinforced rock mass1754 Rock bolting plays an important role in different geo-engineering applications and its numerical modelling is crucial for the analysis and design of rock structures. Continuum modelling simulation of bolt-reinforced rock masses requires specific techniques to properly model the reinforcement system and its interaction with the rock mass, which often exhibits a nonlinear softening/brittle response. In this context, strain localization might occur, which, in turn, may affect numerical convergence and the quality of results. This paper presents some advanced numerical techniques implemented in PLAXIS to overcome the abovementioned challenges. Firstly, a regularization technique is implemented for an extended version of the Hoek-Brown failure criterion with strain softening. Secondly, the formulation of the structural bolt element interacting with the rock mass is developed. Finally, the robustness and accuracy of these techniques are discussed via a numerical example of a typical underground mining excavation problem. | Numerical modelling, Hoek-Brown with Softening, Rock reinforcement, Underground excavations, Viscous regularization
T14: Petroleum engineering and carbon sequestrationChenwang GU (1), Yongcun FENG (1), Nan CHEN (2), Xiaorong LI (1), Jingen DENG (1)1: China University of Petroleum Beijing, Beijing, China; 2: Pengbo Operating Company of CNOOC (China) Co., Ltd, Tianjin, ChinaNumerical investigation of cement sheath integrity under thermo-mechanical coupling based on damage mechanics1756 The transient changes of pressure and temperature in the wellbore during fracturing could cause cement sheath damage and micro-annulus. In this work, a plastic damage model that considers both damage and yielding is used to describe the full stress-strain mechanical properties of the actual cement sheath. A novel numerical model was established to evaluate the cement sheath integrity considering thermo-mechanical coupling. This model is validated by the laboratory experiment and shows high accuracy. The results indicate that tensile damage occurs inside the cement sheath during the fracturing process, and the maximum damage occurs in the direction of the maximum horizontal stress. The micro-annulus rapidly appears at the first cement sheath interface during depressurization process after injection, which can reach 39.57 μm. With the increase of shutdown time, the micro-annulus gradually decreases. This work reveals the cement sheath failure mechanism and provides a basis for wellbore integrity control. | Cement sheath, Thermo-mechanical coupling, Plastic damage, Micro-annulus
T08: Hydropower projects and damsYuxi LIU (1), Qianbing ZHANG (1), Ivan CHING (2)1: Department of Civil Engineering, Monash University, Clayton, VIC, Australia; 2: SMEC Pty. Ltd., Sydney, NSW, Australia3D numerical modelling of stability of underground pumped storage hydropower (UPSH)1757 In light of constructing larger and deeper underground pumped storage hydropower (UPSH) plants in deep valleys, a comprehensive study assesses their stability. Internal and external factors are analyzed for a typical underground hydropower station. Evaluating different rock mass types and mechanical qualities internally, the study also examines various station depths, major horizontal stress ratio (K), station angle, and station length. It is found that increasing station depth and size amplifies stress and deformation of surrounding rock, but rock types with higher compressive strength display better resistance against excavation-induced stress and deformation. Notably, the station walls are more stable when station long axis aligns with the major horizontal stress, but it is expected to be less favorable for station end-wall and tunnels connecting caverns. It is crucial to consider rock properties, in-situ stress, and other key aspects for proper engineering measures for the deeper and larger UPSH plants. | Stability analysis of underground pumped storage hydropower (UPSH), in-situ stress, rock type and quality, cavern length
T05: Digitalization & AutomatisationAmanda HUANG (1), Frank LI (1), Tong Joo SIA (1), Qianbing ZHANG (2)1: SMEC, Australia; 2: Monash University, AustraliaDigitalization and creep modelling for trinocular-cavern based metro station1758 Metro stations are complex underground infrastructure encompassing wide-span caverns. Their interactions with tunnels, adits, and utilities in vicinity can have impacts on ground stability. This paper aims to undertake a novel approach leveraging digitalization of design and 3D numerical modelling to better visualize and quantify the ground-structure interaction based on a metro station featuring a trinocular cavern platform. Knowledge-based prediction is important for critical areas of underground construction. By engaging numerical modelling and using appropriate constitutive relationships for both short- and long-term deformation criteria, predictions into the ground movement and responses of ground support can be made to offer insights into the adequacy of the support system and propose monitoring scheme correspondingly, which forms an essential part of structural health management for the underground infrastructure when coupled with data-driven analytics. | Digitalization, Long-term deformation, Numerical modelling, Trinocular-cavern, Monitoring
T05: Digitalization & AutomatisationDaisuke ASAHINA (1), Takato TAKEMURA (2), Takahisa ENDO (2), Yu TSUKURIMICHI (2), Yu AOJI (2)1: Geological Survey of JAPAN, AIST, Japan; 2: Geomechanics Lab., Department of Earth and Environmental Sciences, Nihon UniversityUsing webcam to visually observe the mechanical behaviors of Shirahama sandstone under triaxial compression1759 We present a newly developed monitoring system to directly visually observe the shear behavior of Shirahama sandstones under triaxial compression testing. The proposed visual monitoring system contains a commercially available webcam and a pressure-resistant steel housing device. The webcam records the video clip of the rock specimen surface during the triaxial compression test. The recorded video frames and their associated digital image correlation (DIC) results allow a better understanding of the evolution of the strain fields and fracture development. The implementation of the proposed monitoring system is simple, safe, and inexpensive, but allow new data to be measure and provides new insights into the progressive shear behavior under triaxial compression loads. | webcam, visual monitoring system, triaxial compression test, DIC, sandstone
T16: Underground storage for liquid and gaseous mediaDaniel Hubert BÜCKEN (1,2), Tobias BACKERS (1)1: Ruhr-University Bochum, Germany; 2: geomecon GmbH, Berlin, GermanyHybrid CO2 based thermo-mechanical underground energy storage - a numerical geomechanical review1760 The energy transition requires new ways of effectively and safely generating and storing energy. Multi-fluid geothermal energy systems, such as flexible CO2 plume geothermal systems and porous medium compressed air energy storage can provide dependable baseload, dispatchable power to complement intermittent renewable energy sources, and underground energy storage capacities. Here, a supercharged hybrid gas-based energy storage (SH-GES) approach using CO2 to store pressure and temperature is analyzed from a geomechanical perspective. This is crucial for safe storage operations. Using fully coupled multiphase THM simulations, a generic fault-bound reservoir model is used to evaluate the effect of cyclic storage operations and variable injection temperatures on stress alterations in and around the reservoirs, shifts in seal integrity, and fault stability. The preliminary findings suggest that employing SH-GES for energy storage is a viable option. However, additional research is needed to gather more data regarding the geomechanical impacts and storage efficiency. | energy storage, compressed gas, THM simulation, geomechanics
T10: MonitoringAlberto MICHELINIIDS GeoRadar, ItalyRegression analysis of slope instabilities evolution for time of failure estimation1762 Time of failure (TOF) estimation of rock slope instabilities is one of the most important output of slope monitoring activities. Providing an accurate TOF estimation allows to significantly mitigate the risk associated with slope failure. Various kinematic models to describe the evolution of instabilities are available in literature, the most representative one is the hyperbolic evolution found by Saito. Different techniques have been proposed and used to fit the Saito model to the experimental data, among these, inverse velocity (IV) method and slope gradient (SLO) method are probably the most popular. However, with the recent development of near real-time monitoring systems, and with modern computing power, it is conceivable to approach the TOF estimation with powerful non-linear regression methods. In the present work, non-linear regression analysis of Saito's model is presented and tested on slope collapse datasets acquired from Ground-Based Synthetic Aperture Radar (GB-SAR) systems. | time of failure, failure forecasting, GB-SAR, slope stability, deformation monitoring
T15: Rock and rock mass propertiesRupesh Kumar VERMA (1), Giang Dinh NGUYEN (2), Murat KARAKUS (2), Abbas TAHERI (3)1: Aurelia Metals, New South Wales, Australia.; 2: University of Adelaide, Adelaide, Australia; 3: Queen's University Kingston, Ontario, CanadaFull-field strain evolution in Brazilian Disc tests using Digital Image Correlation and Adelaide University Indirect Tensile strength test (AUSBIT)1763 Strain energy storing and dissipation characteristics of rock govern the dynamics associated with its failure mode. Such failure, especially in indirect tensile strength tests occurs in a split second, which practically disables the efficient application of image-based instrumentations to obtain the full-field strain evolution during the fracturing process. This paper presents the application of our recently developed innovative experimental methodology, named Adelaide University Snapback Indirect Tensile Strength test (AUSBIT), to indirect tensile testing of strong and brittle rocks. AUSBIT enables control of the disc specimen's cracking process in indirect tensile strength tests and captures the complete class II (snapback) post-peak load-displacement response. These experiments, in conjunction with advanced instrumentations based on Digital Image Correlation (DIC), provide us with full-field strain distributions over the surface of disc specimen. The results obtained are promising, showing both snapback post-peak responses and the evolution of full-field strain distributions. | Brazilian disc, Digital Image Correlation, strain burst, strain energy storing, dissipation, tensile strength
T05: Digitalization & AutomatisationJulia C. GODLEWSKA, Marc S. OGAN, Julia GALLAS, Sarah SCHUMSKI, Mandy DUDA, Tobias BACKERSRuhr-University, Bochum, GermanyComparison between manual and automated determination of discontinuity orientations in different rock mass types1764 In this study, the use of automated discontinuity orientation analysis is evaluated as a potential addition to manual data collection. Point clouds of outcrops of three different rock masses in Germany with distinct structural characteristics are analysed using Open-Source Software Cloud Compare and the plug-in Facets. The accuracy of the automated analysis data is compared to manually collected data. The findings of this study confirm that the discontinuity orientation from automated analysis corresponds to the manually generated data regardless of the geological setting but shows differences caused by exposed area of the discontinuity surfaces and undetected discontinuities due to minimal apertures. Further there remain differences between the results of the methods caused by complex morphology, especially in the context of human bias. The automated approach allows for the investigation of areas that are inaccessible by manual methods, and can also reduce human bias through careful interpretation of the results. | Automated discontinuity analysis, UAV, DOM, photogrammetry
T15: Rock and rock mass propertiesKatharina Meta NEUMANN, Mandy DUDA, Tobias BACKERSRuhr-University, Bochum, GermanyEffect of cyclic thermal loading on a carbonate rock: implications for thermal energy storage1766 Because renewable energy, such as wind and solar energy, is subject to temporal fluctuations, solutions are needed to store the energy in order to use it during periods of low energy production. Sensible thermal energy storage in rock (e.g. Alami et al. 2020) and seasonal geothermal energy storage are two options among some. The cyclic heating and cooling of the rock associated with cyclic storage can cause variations in the rock’s thermo-hydromechanical properties (Fränzer et al. 2023). To understand and specify those changes different rocks from a Jurassic carbonate rock formation in Southern Germany, a formation also targeted for geothermal use, was characterised before and after cyclic thermal loading. We investigated elastic, inelastic and thermal properties before and after thermal treatment to 100 °C and 800 °C. The results contribute to the understanding of thermally-induced changes in properties of rock and rock mass relevant for thermal energy storage. | thermal cycling, sensible heat thermal energy storage, limestone, carbonate rocks, thermal and mechanical properties
T09: Long term behaviour of underground structuresHlomani Glen MTHOMBENI, Shane K. DURAPRAJ, Richard T. MASETHESibanye Stillwater, South AfricaCrush Pillars’ Behaviour at Intermediate Depth on Merensky Reef1767 The Siphumelele Mine orebody has been mined extensively up to a depth of up to 1400 m below surface. Apart from stope support, stability of the reef horizon is provided by regional stability pillars support as well as local “crush pillar” support. These pillars are designed so that they crush as they are being cut, with the residual strength of the pillar material being used for the design. However, the major challenge is to “cut” or mine these pillars to the designed size. Undersized pillars degrade and do not provide the required stability, whilst pillar bursts may occur from oversized pillars. Correctly cut pillars perform as expected; they fracture and provide the necessary support. | Crush pillars, w:h ratio, rockburst, support
T15: Rock and rock mass propertiesMaría RAMÍREZ-BERASATEGUI (2), Diego-José GUERRERO-MIGUEL (1), Ramón GUTIÉRREZ-MOIZANT (2), María-Belén PRENDES-GERO (1), Martina-Inmaculada ÁLVAREZ-FERNÁNDEZ (1)1: DinRock Group. Universidad de Oviedo.; 2: Universidad Carlos III de MadridInfluence of shape surface on the actual stress distribution generated along the contact during the uniaxial compressive strength test1769 Uniaxial compressive strength is one of the key mechanical properties used to characterize rock materials. From international (ISRM) to national (ASTM, UNE) standards have been developed to ensure the trustfulness of testing results. However, they are quite severe with the geometrical tolerances considering the brittleness of rock materials, that provokes the specimens to form chips while machining them during the preparation process. This research analyses the influence of the surface geometrical deviations of the samples during the uniaxial compressive test. The effect of the stress distribution at the contact surface is analyzed using machined metal samples that accurately reproduce controlled flatness deviations. Moreover, pressure films are placed at the contact area to qualitatively record their influence on the actual contact stress distribution. These results are compared to those obtained on rock specimens. Therefore, influence of real contact conditions can be addressed according to the actual machining possibilities of rock materials. | uniaxial compressive strength, contact conditions, experimental contact pattern, load distribution
T03: Deep geothermal energyJuan Miguel REYES-MONTESApplied Seismology Consulting, United KingdomInduced fracture analysis from microseismic catalogues: Salton Sea EGS case study1771 Enhanced Geothermal Systems (EGS) use hydraulic fracturing to create a fracture network that facilitate the circulation of water between injection and extraction boreholes. Microseismic monitoring provides a unique method for the evaluation of the effectiveness and impact of the stimulation and reducing potential risks such as uncontrolled growth or induction of high magnitude seismic events. This study presents tools to interpret the geometry of the induced fracture network and quantify the changes in fluid conductivity induced in the reservoir during stimulations applied to a catalogue of over 8,000 events recorded at the Salton Sea Geothermal field over a 4-year period. The method integrates the temporal, spatial and size characteristics of the induced events to quantify the degree of interaction and connectivity between the fractures within the network, identify enhanced paths for fluid flow and highlight potential zones of induction of larger seismic events. | Microseismicity, Induced seismicity, Enhanced Geothermal Systems, Clustering, Discrete Fracture Network
T09: Long term behaviour of underground structuresSoshi NISHIMOTOCentral Research Institute of Electric Power IndustryLaboratory measurement by geotechnical centrifuge of long-term behavior in a model of vertical emplacement concept with tunnel at a deep geological disposal repository1773 We carried out the centrifuge model test to evaluate the long-term behavior during the resaturation surrounding the deep geological disposal repository. The centrifuge model is the vertical emplacement concept repository and 1/50-size, and the sedimentary rock is drilled a single disposal tunnel and hole, and then the model-overpack, Na-type bentonite buffer, and backfill material are placed in. And the test was conducted at 50 G with the effective stress of 3 MP for equivalent to about 200 years based on centrifugal similarity law. As a result, the displacement of the overpack was measured to be several times larger than that of the tests without the backfill material and disposal tunnel. In addition, it was confirmed that the buffer significantly expanded to the disposal tunnel after the test and visual confirmation. Test results implied that the displacement of the overpack is affected by the stiffness of the backfill material. | Deep geological disposal repository, Long-term THM behavior, Centrifuge model test, Geomechanical interaction
T09: Long term behaviour of underground structuresHermann HÖLD, Bernhard PICHLER, Helmut RECHBERGER, Philipp ASCHENBRENNER, Christian HELLMICHTU Wien (Vienna University of Technology), Vienna, AustriaDissolution and precipitation processes governing the hydration heat development in tunnel cements: Green’s function-based estimation of heat release in modified calorimetric tests1775 Cement hydration in freshly installed NATM-linings may imply significant temperature rises, as has been monitored during the advance of the Granitztal tunnel, as part of the high-capacity railway corridor linking the Baltic and Adriatic regions. These temperature rises affect the overall thermo-chemo-mechanical behavior of the lining and its surroundings, which can be elucidated by a coupled analysis method combining the laws of thermodynamics for chemically reactive media with advanced constitutive modeling and structural mechanics. A key material property entering such computations is the hydration heat per mass of cement, which is the focus of the present contribution. We present a modified calorimetry test where the absolute temperature is measured directly at the boundary of the hydrating cement paste sample prepared in accordance with the provisions at the Granitztal tunnel. This modified calorimetry test give access to the instant heat release rate arising from the hydration process. | Tunnel, Cement, Hydration, Calorimetry, First Peak
T13: Numerical methods in rock engineeringManuel Bernhard WINKLER (1), Ali YAZ (2), Thomas MARCHER (1)1: Graz University of Technology, Graz, Austria; 2: Istanbul Technical University, Istanbul, TurkeyComparison of analytical and numerical solutions for stresses and displacements around unlined tunnels with arbitrary cross sections inside anisotropic rock masses1776 The implementation of closed-form solutions for stress and displacement fields around tunnels with arbitrary geometry, often based on the complex variable theory and the method of conformal mapping, can be quite challenging from a mathematical point of view. In this paper a solution strategy for the implementation of a chosen closed-form solution from literature is presented, including the possibility to account for rock mass anisotropy and arbitrary tunnel geometries. The evaluation of the involved elastic potential functions is described, respectively derivatives thereof, in terms of solving non-linear constrained optimization problems. To validate our approach, the analytical results for stresses and displacements around a tunnel with semicircular geometry are compared to numerical results from finite element computations. The outcome of the study should be regarded as a basis for the development of refined analytical solutions within anisotropic rock masses considering more realistic boundary conditions and effects such as material non-linearity. | analytical solution, complex variable theory, conformal mapping, tunnel displacements, non-linear optimization problem, transverse isotropic rock mass
T13: Numerical methods in rock engineeringSurajit SARKAR, Manoj Kumar TIWARI, Syed Shah Ghalib ASKARI, Indranil SAHA, Piyush SRIVASTAVA, D.B. Sundara RAMAMTata Steel Limited, Jamshedpur, IndiaApplication of empirical and numerical modelling for stability analysis of developmental workings in an underground coal mine1778 Seam XVB of Bhelatand Amalgamated Colliery, Tata Steel Limited, India is being developed in the southern part of the leasehold area where the stability of the overlying roof strata is disturbed due to the presence of geological discontinuities. In this study empirical methods and numerical modelling have been used to ascertain the stability of the workings. CMRI-ISM RMR (Central Mining Research Institute – Indian School of Mines Rock Mass Rating System) classification system is the most popular and practiced empirical method for roof support design in Indian coal mines. Firstly, structural mapping of the panel was carried out in seam XVB. Further, an attempt has been made to estimate the factor of safety of the existing pillars, the rock load on the galleries & junctions of seam roof using both the methods. Finally, using the existing support design, the support safety factor (SSF) was determined, and recommendations were made to improve the existing SSF. | CMRI-ISM RMR, Empirical methods, Numerical modelling, SSF
T05: Digitalization & AutomatisationHans EXENBERGER (1), Ines MASSIMO-KAISER (1), Hannah SALZGEBER (1), Peter KOMPOLSCHEK (2), Frédéric HEIL (3), Matthias FLORA (1)1: AB für Baumanagement, Baubetrieb und Tunnelbau (iBT), Universität Innsbruck; 2: DI Arch. Peter Kompolschek; 3: ÖBB-Infrastruktur AGConcept for Tunnel Information Modelling based work-preview and documentation during construction at Tunnel Angath1779 For the realisation of the ÖBB project Tunnel Angath, the idea was developed to use BIM for various controlling purposes. This publication takes a closer look at the implementation for the areas of work preview and documentation. Derived from established methods of conventional tunnel construction, the necessary models and their data requirements are defined. These include a target model based on the tender, several evolutions of work-preview models as well as singular as-built models, representing each excavation round. All models combined allow for a full documentation of the construction processes and its complete history. The accompanying data structure offers automated dependencies and future-proof expansion capabilities. Finally, this paper presents a concept, which still needs to be proven feasible within the pilot project. | Tunnel Information Modelling, TIM, Building Information Modelling, BIM, Tunnelling, Digitalisation
T01: Challenging rock engineering projectsLianjin TAO, Haixiang ZHANG, Zhibo JIA, Ming SHI, Zhigang WANG, Cheng SHIKey Laboratory of Urban Security and Disaster Engineering of China Ministry of Education, Beijing University of Technology, People's Republic of ChinaStudy on anti-dislocation measures for railway tunnels crossing active faults in complex and dangerous mountainous areas1782 The geological environment of the Tibetan plateau region is complex, with extensive development of active faults. Tunnels built in this area would be greatly affected by active faults. To study the anti-fault measures for the tunnel, active faults were counted along the railway. We then analyze measures to reduce dislocations and review existing fundamental conclusions on fault prevention. Preliminary results on the staggered classification of active faults have been obtained through a literature analysis. Anti-fracture measures that might be applied to the railway were identified. It includes the use of segmental composite lining structure (such as steel-mixed composite structure), improving the stiffness of flexible articulated joints (such as corrugated steel), increasing the width of articulated joints, fault fracture zone core expansion design and other measures. The results can be used as a basis for a quantitative study of anti-fracture measures. | Mountain railway tunnel, active faults, anti-dislocation measures
T13: Numerical methods in rock engineeringVaibhav SHRINGI, Manuel Bernhard WINKLER, Alexander KLUCKNER, Thomas MARCHERGraz University of Technology, Graz, AustriaEvaluation of trends in tunnel lining utilization with regard to the moment of ring closure1784 At sequenced tunnel drives, next to the rock mass conditions, the advance rates of the single excavation stages and the moment of ring closure determine the performance of shotcrete linings. Especially in heterogeneous rock masses, the investigation of the optimum ring closure moment resulting in no damage of the lining challenges the engineers. If the ring closure is too early, the lining may experience compressive failure because the building up of ground loads is too large. A late ring closure may allow for too much tunnel displacement. To investigate the effects of various ring closure moments on the utilization of the tunnel lining and the tunnel crown convergences, this study performs 3D finite element simulations. The results at a specific measuring cross section and for the assumed ground conditions suggest that a delayed ring closure can lead to higher utilizations compared to an early ring closure. | ring closure, 3D finite element simulation, lining utilization, sequential excavation
T04: Deep mining and tunnellingChen XU (1,2), Lingxiao ZHENG (1), Gecheng ZHANG (1), Qing YAO (1), Shikang QIN (3)1: Institute of Rock Mechanics, Ningbo university, People's Republic of China; 2: Ningbo Key Laboratory of Energy Geostructure, Ningbo, China; 3: College of Civil Engineering, Tongji University, Shanghai, ChinaApplicability of stress release method in soft rock tunnel with high geostress1785 The Deformation Reserved (DR) method is a commonly used stress release method in the construction of weak rock tunnel with high geostress. The excavated tunnel section is usually larger than its design size, a space is reserved outside the design excavation boundary of the tunnel. The behavior of the double-layer support structure was investigated through theoretical derivation, and the applicability of the DR method in controlling the large deformation of soft surrounding rock during tunnel construction in high geostress was discussed. The calculated results by proposed method were verified by the in-situ monitoring data of field test. It is found that the DR method is capable of releasing the high geostress when tunnelling in squeezing rocks, and the double-layer support structure is necessary to resist the high ground stress. | large deformation, in-situ monitoring, multi-layer support, Deformation Reserved method, stress release
T15: Rock and rock mass propertiesMaximiliano R. VERGARA (1,2,3), Ana LIBREROS (4), Karl BALTHASAR (3)1: Skava consulting SA, Providencia, Chile; 2: Skava consulting ZT, Salzburg, Austria; 3: Institute of Soil Mechanics and Rock Mechanics, Karlsruhe Institute of Technology, Karlsruhe, Germany; 4: Ed. Züblin AG, Zentrale Technik - Tunnel Engineering, Stuttgart, GermanyExperimental and numerical study on the creep behavior of a rock mass with filled joints1786 The time-dependent behavior of the rock mass is primarily controlled by the time-dependent deformation of the rock mass discontinuities. While most investigations concerning creep in rock masses have focused on the creep behavior of the intact rock, there is limited experimental data available on the creep behavior of rock fractures and discontinuities. In this study, direct shear creep tests were carried out on rough and saw-cut rock joints artificially filled with ground rock to investigate the creep behavior of rock fractures in the laboratory. The experimental results demonstrate that the creep deformation and failure potential in a filled joint depends on the shear-stress/shear-strength ratio, the magnitude of the shear stress, and filling thickness. Subsequently, the observed creep behavior of the rock joints was implemented into a numerical model to simulate the creep response of a jointed rock mass with varying fracture densities. | Rock joint creep, Rock mass creep, Joint shear creep test, Rock mass creep model
T13: Numerical methods in rock engineeringKyeunghye AHN (1), Amade POUYA (1), Gye-Chun CHO (2)1: Laboratoire Navier (Université Gustave Eiffel, CNRS, ENPC), Ecole des Ponts ParisTech, Marne-la-Vallée, France; 2: Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, South KoreaModeling of joints of segment linings under complex relation between lining and ground conditions1789 This study has been attempted to do segment lining modeling by researching the effects on joints between segments. There were limitations in modeling analysis considering complex ground conditions along with joins. For example, it is often used to analyze the lining behavior due to joints in elastic ground like the beam-spring model or to analyze intensively the ground behavior by simplifying it. However, since consideration of elasto-plastic ground conditions and behavioral analysis of segment by joints are both important parts that influence each other, it can be said that modeling analysis is appropriate when analyzed together. To this end, the numerical analysis (FEM-code Disroc) was performed on the relationship of the interface between the ground and the lining by applying the segment joint as a nonlinear elastic model (Bandis). It is also reminded of the need for analysis depending on the presence or absence of joints in ever more complex ground. | Joint, interface, tunnel, nonlinear elastic
T15: Rock and rock mass propertiesLucas Conrad WITTE, Mandy DUDA, Murat AYDIN, Hossein ASGHARI CHEHREH, Tobias BACKERSRuhr-University Bochum, GermanyGeomechanical characterization of two granites to establish an experimentally based benchmark for numerical simulation – a laboratory study1790 Since decades, numerical models have been used to predict the behavior of the subsurface in civil and geological engineering projects. The validity of these codes must be tested against field observations or, more often, apparently simple laboratory experiments, whose outcome is typically known to the modeler. Therefore, there is a distinct need for an objective procedure to verify if codes are capable to mirror and predict supposedly simple, physical processes. In this Study we have determined microstructural properties, geometric and grain densities, ultrasonic wave velocities, static moduli, uniaxial compressive strengths, tensile strengths, the time dependence of geomechanical properties, thermal and hydraulic properties. | Rock mechanics, rock mass properties, laboratory experiments, granite
T13: Numerical methods in rock engineeringShahabedin HOJJATI (1), Hassan POURARIA (2), Seokwon JEON (1,3)1: Research Institute of Energy and Resources, Seoul National University, Seoul, Republic of Korea; 2: Department of Chemical and Materials Engineering, New Mexico State University, Las Cruces, NM, USA; 3: Department of Energy Systems Engineering, Seoul National University, Seoul, Republic of KoreaNumerical modeling of erosion in dense slurry flows1791 Dense slurries are often produced and transported in mining engineering. Handling such high-volume fraction particulate flows often results in high pressure drop and severe erosion damage in facilities. Underestimating the erosion damage may result in catastrophic health, safety and environmental problems. The present study aims at modeling erosion in dense slurries by using computational fluid dynamics simulation. We use dense discrete particle model which takes into account both particle-fluid and particle-particle interactions. Numerical modeling is first conducted for a slurry impingement test with available experimental data through which the accuracy of the model is validated. Then, CFD simulation is conducted for a flow loop transmitting slurry flow. A comparison of the obtained CFD results with measured erosion rate (R2=96.05%, mean percentage error=11.24%) indicates a great potential of DDPM for modeling erosion in dense slurries. | Erosion, dense slurries, Numerical modeling, DDPM
T06: Geological investigation and characterizationHong-Gyu LEEOriental Consultants Global, Tokyo, JapanPavement failure and flooding of tunnel in limestone geology1792 This paper describes a case study of cause investigation and countermeasure on pavement failure and flooding in a under service tunnel during a heavy rain constructed by NATM in limestone geology. Since caverns of various sizes were confirmed and a large amount of groundwater flowed into the tunnel during the excavation, the cause is assumed to be the high water pressure acting on the caverns connected to the lower part of the pavement, which could not be visually confirmed when the tunnel was excavated. After confirming the soundness of the tunnel structures and pavement concrete by non-destructive testing methods, the cause investigation mainly focused on reconfirming the original excavation surface under the tunnel pavement. A countermeasure was adopted to allow free drainage through the confirmed small caverns and new drilling holes to prevent the reoccurrence of high water pressure in the small caverns around the tunnel. | Limestone, tunnel, cavern, water pressure, pavement failure, countermeasure
T15: Rock and rock mass propertiesMaría Elvira GARRIDO (1), José B. SERÓN-GAÑEZ (1), Víctor MARTÍNEZ-IBÁÑEZ (1), Carlos HIDALGO-SIGNES (1), Roberto TOMÁS (2), Martina-Inmaculada ÁLVAREZ-FÉRNANDEZ (3)1: Universitat Politècnica de València, Spain; 2: Universidad de Alicante; 3: Universidad de OviedoPoint Load Strength Index of a limestone exposed to high temperatures and correlation with uniaxial compressive strength1793 The most common procedure to obtain rock strength is the uniaxial compressive strength test (UCS). Extracting rock samples weakened by temperature can affect the estimation of the UCS values. Estimating UCS using the Point Load Test (PLT) is possible because both are linearly related. PLT needs smaller samples and is quicker and cheaper than the UCS test. This research determines UCS, Point Load Strength Index, and β-values (i.e., the ratio between UCS and Point Load Strength Index) of a limestone exposed to temperatures up to 900°C and then cooled on air or by immersion in water. Results show that strength and β-values decrease as temperature increases. There are two threshold temperatures in the relationship between point load strength and UCS in Pedra de Borriol samples: 600 ºC for samples subjected to slow cooling and 400 ºC for those subjected to quick cooling. | UCS, PLT, limestone, high temperatures, Pedra de Borriol
T15: Rock and rock mass propertiesRisto KIURU (1), Sophie HAAPALEHTO (2)1: Oy Rock Physics Finland Ltd, Finland; 2: Posiva Oy, FinlandModified transient plane source measurements of Olkiluoto migmatite1795 Finland is moving forward as the first country to solve the geological final disposal of spent nuclear fuel. Due to the temperature sensitive nature of the used disposal method, thermal design of the repository layout is necessary. This design process requires information of the thermal properties of the rock mass as confining parameters for modelling. As part of this process, modified transient plane source (MTPS) measurements of the thermal properties of Olkiluoto migmatite were carried out between 2019 and 2021. The MTPS method was used to measure simultaneously thermal conductivity and thermal effusivity. Additionally, density measurements were done, allowing the calculation of thermal diffusivity and specific heat capacity. The assumption of normally distributed data was tested using the Shapiro-Wilk test for normality and normal probability plots. Finally, the data were fitted with Gaussians using the maximum likelihood method. | geological disposal, thermal properties, thermal conductivity, thermal effusivity. modified transient plane source, MTPS
T13: Numerical methods in rock engineeringNicolas GONZE, Fanny DESCAMPS, Jean-Pierre TSHIBANGUUniversity of Mons, Mons, BelgiumDevelopment of a 3D discrete element method approach to study the evolution of rock cutting mechanism in high-depth conditions: application to Vosges Sandstone1796 While wells reach deeper and deeper targets, understanding the cutting mechanism under confinement is not yet fully mastered. Among the numerical methods used to study this problem, the Discrete Element Method has already shown promising results, but the evolution of rock behavior with confinement is not always considered. This work proposes a calibration method based on UCS and triaxial tests to represent the evolution of rock behavior with confinement. This calibration procedure is implemented on Vosges Sandstone. The rock model failure envelope is built based on further triaxial tests and agrees with the experimental one. Secondly, linear cutting tests under confinement were implemented on the calibrated model. The results are compared to experimental ones. Their good agreement allows the validation of the proposed approach. | DEM, model calibration, rock cutting, confinement, PDC
T06: Geological investigation and characterizationEmelie GAGNON, Jennifer J. DAYQueen's University, CanadaInterpreting variability of uniaxial compressive strength with insights from vein microstructures1797 The uniaxial compressive strength (UCS) test is regularly used to derive rockmass strength and stiffness properties for geomechanics numerical modelling. While the test is straightforward, selecting representative material properties from a testing suite constrained by economics relies on the practitioner’s experience. This is challenging in veined rocks that exhibit significant variability in the results. To reduce this uncertainty, this study investigates the influence of intravein grain-scale geometric heterogeneity and orientation on the emergent veined specimen strength. Veins exhibit a spectrum of microstructures depending on the geological boundary conditions during their formation. Here, this is captured in a suite of 2D finite-element grain-based UCS experiments on specimens containing a single calcite vein. Results indicate that intravein grain orientation in veins with anisotropic grain arrangements is as influential on strength as the overall orientation of the vein (15-85% strength reduction) while isotropic crystal-bridged veins are less sensitive to orientation (20-45% strength reduction). | Geomechanical laboratory testing, uniaxial compressive strength (UCS), hydrothermal veins, grain-based modelling (GBM), vein microstructures
T14: Petroleum engineering and carbon sequestrationYong SHENG (1), Bing BAI (2), Jinzhi ZHU (1), Zexv ZHANG (2), Haiying LU (1), Mian CHEN (2), Yunhu LU (2)1: Tarim Oil Field Company, Petro China; 2: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing)Mechanism of wellbore collapse for Carboniferous, Ordovician and Cambrian strata in Southwestern Tarim of China1798 Samples corresponding to severe wellbore collapse in Carboniferous, Ordovician and Cambrian strata were collected from oil field company according to drilling and logging data. In this study, X-ray diffraction, hydration inhibition (linear swelling, dispersion and cation exchange capacity) tests and SEM experiments were conducted on representative samples. With the combination of caving analysis, the mechanisms of wellbore collapse were investigated for specific strata in Southwestern Tarim. The results showed that in Carboniferous strata, wellbore collapse was the comprehensive results of mudstone hydration and the existence of weak planes. In Ordovician strata, it could be concluded that the existed natural fractures providing drilling fluid flow path was the dominant factor inducing the wellbore instability. In Cambrian strata, the results showed the salt dissolution was the main reason of borehole collapse. | Hydration inhibition, Microstructure, Caving analysis, Wellbore stability, Southwestern Tarim
T13: Numerical methods in rock engineeringLong CHEN (1), Xin ZHANG (2), Li ZHAO (1), Bao ZHOU (1), Yan DING (3), Yunhu LU (2), Yutian HAN (1)1: PetroChina Tarim Oilfield Company, Korla, China; 2: College of Petroleum Engineering, China University of Petroleum Beijing, China; 3: CNPC Engineering Technology R＆D Co., Ltd., Beijing,ChinaA post-stack seismic sparse dictionary learning inversion method based on logging data - A case study of the Tarim Basin1802 Highly accurate seismic inversion results help refine geomechanical modeling. In this paper, a post-stack seismic sparse dictionary learning inversion method based on logging data is proposed. First, feature functions are extracted from the logging data. Then, a dictionary is learned adaptively from known observations. This dictionary is composed of a series of feature functions, using which the parametric model can be effectively characterized. This method effectively avoids the problem of single mathematical model assumptions. Finally, the post-stack wave impedance inversion data are solved, and the separation of wave impedance data is performed using the correlation between the velocity data and the density data. This method can effectively improve the resolution of seismic inversion results by extracting a priori information from logging data. It is found that the root-mean-square error of the sparse dictionary learning method is reduced by 9.075% compared to the Tikhonov method. | sparse dictionary learning, seismic inversion, highly accurate, geomechanical parameters
T14: Petroleum engineering and carbon sequestrationYiqi ZOU, Xuyue CHEN, Deli GAO, Siyuan YIN, Qiqi YANGChina University of Petroleum, Beijing, ChinaThe challenge of ocean shallow extended reach wells: how to achieve a farther extension limit1803 Due to the shallow vertical depth, offshore shallow extended reach wells usually have a high horizontal displacement to vertical depth ratio. The high friction of drill pipe during drilling limits the extension capacity of the extended reach well. Based on the three-dimensional string mechanical model, this paper analyzes the extension limit under the drilling condition and maximum running depth of 9-5/8 ″ casing under casing running conditions, and concludes that the friction coefficient, wellbore trajectory and drilling equipment are the main parameters limiting the extension limit. The operation parameters and suggestions under different working conditions are given.This research is expected to increase the extension limit of shallow extended reach wells and promote the economic and efficient development of shallow oil and gas. | extended reach well, extension limit, shallow water, downhole string
T17: Rock slope engineeringMazlina RAZALI (1,2), Mohd Ashraf MOHAMAD ISMAIL (1), Sharan Kumar NAGENDRAN (3), Zuraini ZAINAL (3), Hayato TOBE (4), Kensuke DATE (5), Yasuhiro YOKOTA (5), Hamzah HUSSIN (6)1: School of Civil Engineering, Engineering Campus, Universiti Sains Malaysia, Penang, Malaysia; 2: Centre for Civil Engineering, Universiti Teknologi MARA, Cawangan Pulau Pinang, Permatang Pauh Campus, Pulau Pinang, Malaysia; 3: Centre of Excellence for Engineering and Technology (CREaTE), Public Works Department (JKR), Alor Gajah, Melaka, Malaysia; 4: Rock Mechanics and Hydro-geology Group, Kajima Technical Research Institute, Kajima Corporation, Japan; 5: Kajima Technical Research Institute Singapore, Kajima Corporation, Singapore; 6: Department of Geoscience, Faculty of Earth Science, Universiti Malaysia Kelantan, Jeli, KelantanEvaluation of weathering effects by CIELAB color space and image analysis technique for interbedded metasedimentary rock in the northern region of Peninsular Malaysia1805 Weathering process affect the engineering behavior of rock masses, reduced strength, and structural stability. In addition to the prior technology, rapid weathering evaluation by CIELAB to characterize the rock surface color. The various colors appearing on the surface of the rock slope indicated the differential weathering grades of the rock mass. UCS-Schmidt obtained by the Schmidt hammer strongly validates the color changes and can be classified into different grades. A high value in redness (a*) and yellowness (b*) indicates the rock is weathered. The results were further revealed using image analysis to confirm the analysis. The weathering zoning processed by image analysis clearly interpreted different weathering grades. This study revealed the enhanced technique as an effective tool in the preliminary evaluation of weathering effect. | Image analysis, weathering, metasedimentary rock, CIELAB, Schmidt hammer
T12: New developments in rock supportGünther M. VOLKMANNDSI Underground Austria GmbH, AustriaVerification of design relevant parameters for new pipe umbrella support systems1806 Since the 90s pipe umbrellas have been used regularly to support tunnel headings in difficult ground conditions. During this time, the rules for design have continuously improved, but there are still problems to determine the equivalence of alternatively offered, new systems. For this reason, common connection types for pipe umbrella support systems are described and their characteristic design parameters, their advantages and disadvantages reviewed. Two different design approaches will be introduced and discussed. Different connection types or staggered connections / joints are assessed regarding their influence on the load-bearing capacity. The results of laboratory tests are discussed, and the necessity of a statistical evaluation shown. Having these results presented in a laboratory test report or a certificate issued by the producer in hand, it is possible to define for an owners representative whether alternative connection types are adequate or not. | pipe umbrella, canopy tube, design approach, connection types, laboratory bending tests
T05: Digitalization & AutomatisationAna Raquel Sena LEITE, Hatem MRADUniversité du Québec en Abitibi-Témiscamingue, CanadaThe creative process for the development of an autonomous bolting arm for underground mines1807 Ground support installation is essential in the underground mining industry. However, it is one of the riskiest activities due to the operator's exposure to unsupported faces recently excavated. From this reality, this work was performed to develop autonomous drilling and bolting arm for underground support purposes. The primary considerations for machinery are the rock mass interaction, artificial intelligence for recognition and mechanical requirements. First, some of the latest technologies that can be related to this research of the autonomous underground mine will be discussed. Secondly, the insight from the miners obtained from interviews will be reported. Finally, the challenges, premises and steps taken will be discussed. This research cannot be compared to one standard automatization due to the extreme variability encountered in rock masses during excavations. | Autonomation, machine learning, rock mechanics, ground support
T15: Rock and rock mass propertiesVasileios KALLIMOGIANNIS (1), Charalampos SAROGLOU (1,2)1: National Technical University of Athens, Greece; 2: University of Leeds, UKMechanical properties of carbonate fault rocks1809 The tectonic processes that take place inside a fault zone change the initial structure of the parent rocks and impact their properties. In the present study, the mechanical properties of five (5) types of carbonate fault rocks from Lefkada Island, Greece, are investigated and compared to the corresponding properties of the parent carbonate rocks. Due to their tectonic disturbance and weak nature, the studied fault rocks are difficult to sample and test using the methodologies suggested by the international standards in Rock Mechanics (ISRM, ASTM). Therefore, a new methodology to sample and perform laboratory tests in such materials is used. The mechanical properties of each studied type presented a high variance which relates to the different structural and textural properties of the tested samples. Those properties were quantified to shed light on the factors that control the strength of the studied fault rocks. | Carbonate fault rocks, Mechanical properties, Structural properties, Textural properties, Sample preparation, Uniaxial Compressive Strength
T10: MonitoringAdolf Bernd MORITZ (1), Johannes FLECKL (1), Werner LIENHART (2), Johann GOLSER (3), Thomas PILGERSTORFER (4)1: ÖBB-Infrastruktur AG, Graz, Austria; 2: Graz University of Technology, Austria; 3: Geodata, Leoben, Austria; 4: Geoconsult ZT GmbH, Puch bei Hallein, AustriaLong-term monitoring of Austrian railway tunnels – A next step forward1811 At the large infrastructure projects of the Austrian Federal Railways OeBB in the Alpine region geotechnical structures with different characteristics are encountered. Especially fault zones associated with high overburden are a great challenge during tunnelling, often resulting in large deformation of the rock-support system. On the other hand support for tunnels in swelling ground has to be designed to an expected swelling pressure during the life time of a tunnel. The goal is to apply robust, reliable and durable monitoring systems for observing such geotechnical structures during a service life of the tunnels of 150 years. The benefit is to early detect unfavourable tendencies of the system behaviour and the planning of measures in terms of predictive maintenance accordingly in due time. Finally this ensures high availability of the tunnels during operation. The paper presents the implementation of long-term monitoring via the projects Koralm Tunnel, Granitztal Tunnel and the Semmering Base Tunnel. | long-term monitoring, OeBB railway tunnel, ground pressure, fibre optic sensing, vibrating wire strain sensors, automatic data acquisition
T15: Rock and rock mass propertiesVasileios KALLIMOGIANNIS (1), Charalampos SAROGLOU (1,2)1: National Technical University of Athens, Greece; 2: University of Leeds, UKClassification of weak, carbonate fault rocks1812 The most common rock mass classification systems have been developed around hard rocks and do not fully apply to the characterization of weak rocks. Moreover, fault carbonate rocks present unique properties that cannot be accounted for when using these systems. Therefore, a new classification scheme is needed to accurately predict their mechanical properties. Weak, carbonate fault rocks from Lefkada island, Greece, are studied via a series of laboratory tests. Based on the geological background and our findings, the fault rocks are classified into four main types: Parent rocks, Welded breccias, Unwelded breccias and Matrix material. A methodology to estimate the Uniaxial Compressive Strength (UCSi) of each fault rock type is proposed. The results indicate that the Uniaxial Compressive Strength of the welded/unwelded breccias is a function of the corresponding strength of their components (fragments and matrix) and the matrix ratio (the percentage of matrix in a given volume). | Carbonate fault rocks, Mechanical properties, Structural properties, Textural properties, Sample preparation, Uniaxial Compressive Strength
T04: Deep mining and tunnellingRajashekar Yadav AVULA, Sreenivasa Rao ISLAVATHIIT KHARAGPUR, IndiaAnalysis of the behaviour of the Barrier Pillars and Gateroads of the deep Longwall Panel of India using the 3D Finite Element Modelling approach1814 In Longwall mining, gateroads play a major role in transporting men and materials and providing ventilation. Barrier pillars lie between two adjacent panels to support the face and gateroads. During the retreating, these gateroads and barrier pillars are subject to mining-induced stresses and may cause the failure of the face, barrier, roof and floor of gateroads. The behaviour of barrier and face must be assessed to extract the panel successfully. For this, a longwall panel of 250 m x 2500 m size lying at 530 m depth is analysed using 3D finite element modelling technique. This study considers the variations in retreat distance, coal properties, and barrier size. All the numerical models are analysed considering Mohr-Coulomb criterion. The vertical displacement in gateroads and stress on the barrier and longwall face, abutment zone and yield zone are analysed, and the safety factor of the barrier pillars and longwall face are determined. | Barrier pillar, Gateroad, Development of load, Goaf, Safety factor
T15: Rock and rock mass propertiesVíctor MARTÍNEZ-IBÁÑEZ (1), Carlos HIDALGO SIGNES (1), María Elvira GARRIDO (1), José Bernardo SERÓN GÁÑEZ (1), Roberto TOMÁS (2), Celestino GONZÁLEZ-NICIEZA (3)1: Universitat Politècnica de València, Spain; 2: Universidad de Alicante, Spain; 3: Universidad de Oviedo, SpainVariation in the drilling rate in thermally treated limestones through penetration-time curves from Sievers’ J-miniature drill tests1817 In this research we subject Prada limestone samples to temperatures of 600 ºC, and then we perform Sievers’ J-miniature drill tests to study the evolution of the penetration over time. We identify two characteristic intervals in the penetration–time plots: a superficial region with a variable penetration rate that includes an initial maximum value, and a deeper region in which the penetration rate stabilizes. Thermally treated samples exhibit an increase in the initial and final penetration rates, which indicates thermal damage both superficially and in-depth. We also observe that the time necessary to reach a stable drilling rate dramatically increases with temperature, involving an important part of the total test time. That has a clear influence on the final SJ value from Sievers’ J-miniature drill tests and is a starting point to determine a corrected SJ value for thermally treated limestones. | Rock drillability, Sievers’ J-miniature drill tests, SJ value, Thermal treatment, Temperature, Limestone
T04: Deep mining and tunnellingTawanda ZVARIVADZALuleå University of Technology, SwedenA conceptual study on the prediction of destress blasting efficiency using geostatistical approaches1819 As underground mines go deeper, it is of utmost importance to manage increased stresses to minimise occurrences of rockbursts. Rockbursts have several documented devastating economic, social and safety consequences such as fatalities, loss of mine assets or production sections, social uproar, force majeure etc. Among several approaches which can be adopted to manage rockbursts is the practice of destress blasting. It is necessary to evaluate the efficiency of any adopted destress blasting design. This can be done through the measurement of physical parameters such as changes in deformation, local seismic magnitude, stress; fracturing intensity etc. at different locations where destress blasting has been implemented. This entails physical exposure of workers to mining excavations, increasing their exposure to harm when safety fails. This paper presents a conceptual study on geostatistical approaches which can be utilized to estimate unmeasured locations using measured locations, thereby reducing the mining personnel's exposure to harm. | Deep mining, Rockburst, Destress blasting, Geostatistics, Semi-variogram modelling, Cross-validation
T13: Numerical methods in rock engineeringSteffen BEESE, Ralf EICKEMEIER, Jobst MASSMANN, Sandra FAHLANDBGR, GermanyAnalysing the influence of finite deformations treatment towards the safety assessment of nuclear waste repositories1820 In the analysis of underground disposals over multiple thousands of years the assumption of small strains can be violated. In this contribution an extension of the BGRc creep model to the finite deformation regime is outlined. With small scale examples the finite deformation treatment of the underlying boundary value problem is studied towards its influence on safety assessments for geological nuclear waste repositories. | Finite Deformation, Rock Salt, Creep, Finite Element Method
T13: Numerical methods in rock engineeringHarry HOLMES (1), Chrysothemis PARASKEVOPOULOU (1), Mark HILDYARD (1), Krishna NEAUPANE (2), David CONNOLLY (1)1: University of Leeds, United Kingdom; 2: AECOM, United KingdomEffect of joint dip on the transmission of stress waves from a moving point load in a parallel jointed rock mass1821 This paper presents a comparison between the response of an isotropic continuum and a jointed discontinuum when subject to a moving point load source. A numerical model was setup in the Universal Discrete Element Code (UDEC) and a tunnel was modelled longitudinally as nodes within the model. Discontinuum models with four different joint angles and a single isotropic continuum were analysed with the relatively near field and far field vertical displacement from each model recorded. It was found that the discontinuum models can show more or less displacement than the isotropic continuum depending on the joint angle. The patterns of the response were found to be different in the far field and near field. Conclusions were drawn relating to considerations for the best practice for commercial modelling of railway vibrations. | Jointing, Rock Engineering, Moving Load, Underground, Vibrations
T08: Hydropower projects and damsSteffen BAUER, Sebastian PERZLMAIERTIWAG-Tiroler Wasserkraft, AustriaThe material extraction for the Kühtai Dam1823 For the construction of the Kühtai embankment dam, a total fill volume of 6.9 mio m³ is required. The main sources of the material are the overburden and hard rock of the Längental valley. The required rock material is produced in a quarry developed at the eastern reservoir slope. The rock mass consists mainly of granodiorite gneiss. To estimate the production volume a 3D rock contour model was developed. The total production volume is 2.2 mio m³ of hard rock and 3.2 mio m³ of overburden. The produced material has to fit the requirements of the dam zoning, considering mass balance and sequence of construction. The bench and overall slope stability is evaluated by stability calculations, visual inspections, engineering-geological mapping, geodetic monitoring and terrestrial laser scanning. The finale bench faces are blasted by pre-splitting method. Preparation for production has started in 2020 and production began in 2022. | Kühtai Dam, rock slopes, quarry, blast design, monitoring
T15: Rock and rock mass propertiesSai Srujan Kumar CHALAVADI (1), Mahendra SINGH (1), Yogendra SINGH (1), Jaysing CHOUDHARI (2)1: Indian Institute of Technology Roorkee, Roorkee, India; 2: Fortescue Metals Group Ltd, East Perth, West AustraliaEffect of scale and in-situ stress ratio on the deformation modulus of rock mass around tunnels1824 Assessment of rock mass modulus is an essential part of analysis and design of tunnels. An in-house study was conducted to understand the variation of rock mass modulus around a tunnel to changing joint characteristics and far-field in-situ stress ratios. In each test, tunnel support pressures and displacements at the boundary of the test specimen were monitored. An exhaustive analysis of test results revealed that the deformation modulus is more sensitive to varying in-situ stress ratio than joint orientations. The modulus is found to decrease with increasing stress ratio. In addition to in-house study tests, analysis of the laboratory test results on jointed rock and small-scale rock mass specimens from literature proved a profound scale effect on deformation modulus. | Tunnels, Rock mass modulus, Joints, Joint factor, Scale effect
T15: Rock and rock mass propertiesLars JACOBSSON, Mathias FLANSBJER, Jörgen LARSSONRISE Research Institutes of Sweden AB, SwedenDirect shear tests on large natural and artificially induced rock fractures in a new laboratory equipment1827 A direct shear equipment for testing rock fractures up to 400×600 mm size, and up to 5 MN force in both normal and shear loading directions, was developed. Normal loading and direct shear tests under constant normal stiffness (CNS) and constant normal load (CNL) conditions were conducted on 300×500 mm specimens, one planar steel joint and two natural and two tensile induced rock fractures. Design targets, e.g. system to maintain undisturbed fractures up to testing and high system stiffnesses to achieve well-controlled shear tests, were verified by the experiments. A new optical system for local deformation measurements was used to accurately determine fracture displacements besides conventional non-local deformation measurements. The determined normal stiffnesses were similar previous results from the literature on smaller fractures, whereas the shear stiffness data are novel. The results provide a new insight into processes at the onset of fracture slip. | Rock fractures, large scale direct shear equipment, local optical deformation measurements, CNL, CNS, fracture stiffness
T15: Rock and rock mass propertiesDiego-José GUERRERO-MIGUEL (1), Martina-Inmaculada ÁLVAREZ-FERNÁNDEZ (1), María-Belén PRENDES-GERO (1,2), Celestino GONZÁLEZ-NICIEZA (1), Covadonga BETEGÓN-BIEMPICA (2), Emilio MARTÍNEZ-PAÑEDA (3)1: DinRock Group, University of Oviedo; 2: Construction and Manufacturing Engineering Department. University of Oviedo; 3: Department of Civil and Environmental Engineering, Imperial College LondonNew testing equipment to study dynamic fracture of rock and cement-based materials subjected to the action of roadheaders1828 New customized testing equipment specifically developed to address the dynamic fracture of material excavated by a roadheader at a laboratory scale is shown. Furthermore, limestone and cement-based material samples are tested to analyze the response of both the material and the cutting head when the number of acting picks is increased as a consequence of the translation of the whole roadheader during the excavation process. Results prove that the new equipment allows to identify the initial and end points of the contact between the sample and each of the picks, as well as the relation between the material strength and the mechanical specifications of the excavating machine. Thus, the new equipment can be used to tailor cutting head designs and to optimize the cutting parameters for a particular mechanical removal operation. | dynamic fracture, roadheader, excavation, rock cutting
T18: Early Career Forum (Young Researchers)Renato PEREIRA, José MURALHA, Luís LAMASLNEC, PortugalStability analysis of a rock slope: Fully-probabilistic approach1830 Stability analysis of rock slopes is an exercise that poses a variety of challenges to a rock engineer. Field information is often lacking and subjective modelling of the rock mass is required. Expert judgment also influences the quantification of the targeted safety level, reflecting the confidence of the designer in his own assumptions and hypothesis. With the introduction of the EN1997 in Europe, structural reliability concepts were brought to the design of geotechnical structures, now also including rock masses after its current revision. Yet, fully-probabilistic methods are still considered valid alternatives to the partial safety method recommended there. Understanding how to address rock engineering problems from a probabilistic perspective becomes essential to move beyond the traditional practice. In this study, a simple problem relating to the stability of a rock slope is explored. Limit states for foreseeable failure mechanisms are defined and the system reliability problem is formulated and solved. | Rock slope, wedge stability, probabilistic approach, system reliability, failure mode analysis
T08: Hydropower projects and damsMike GEORGEBGC Engineering, United States of AmericaA Block Theory approach for rock erodibility assessment incorporating 3D high-resolution site characterization data1831 Scour of rock in dam foundations and spillways during flood events is an important issue for dam safety. A new approach using Block Theory to evaluate erodibility of 3D rock blocks has been developed using physical hydraulic model and prototype testing. The use of high-resolution remote sensing technology for 3D site characterization of the rock mass (e.g., photogrammetry and LiDAR) in combination with the Block Theory Rock Erodibility (BTRE) method has permitted a more detailed, site-specific, examination of rock erodibility than previously attainable. This includes delineation/analysis of site-specific 3D rock blocks, monitoring/change detection of scour over time, and rapid collection of thousands of discontinuity measurements for probabilistic scour analysis. | Rock scour, Block Theory, remote sensing, erodibility, dams, spillways
T17: Rock slope engineeringLal HRUAIKIMA (1), Mahendra SINGH (1), Sarada Prasad PRADHAN (1), Jaspreet SINGH (2)1: Indian Institute of Technology Roorkee, Roorkee, India; 2: Simon Fraser University, Burnaby, BC, CanadaSite specific joint spacing distribution of roadcut slopes in a selected stretch of national highway in Indian Garhwal Himalayas1833 Due to extensive road widening project in the Himalayas, the roads experience huge instability problems especially during monsoon season. For the present study, 50 rock slope sites were considered over a stretch of 35 km on a national highway. The various attributes of discontinuities governing the slope failure were observed and the joint spacing in the stretch of the national highway is studied in detail. Detailed scanline survey was carried out and a database comprising more than about 6000 datapoints was generated. It is observed that the joints are spaced between 1 cm to 60 cm for the stretch of road. Statistical analysis of the joint spacing shows that most of the joint sets follow Exponential distribution, Weibull distribution, and lognormal distribution. Slope stability analysis was performed using the joint spacing data for all the slopes. It was observed that 50% of the slopes were susceptible to failure. | Discontinuities, Joint Spacing, Probability Distribution, Slope Stability
T04: Deep mining and tunnellingTobias BACKERS, Simon KATTENBECK, Mandy DUDARuhr-University Bochum, GermanyThe Brown-Hoek stress-depth relation revisited1835 In 1978 Brown and Hoek published their well-known paper on the relationship between measured in-situ stress and depth. The key figure of this paper can be found in many textbooks related to rock mechanics and rock engineering and the given relationships are used frequently. In this paper we use the World Stress Map data to check if the more than 40 years old interpretation of the limited dataset at that time is still valid. The presented analyses clearly shows that the general trends are, but that some details need to be tuned in future. In an ongoing initiative more measured stress data is included into the analysis. | in-situ stress, horizontal stress, depth-related, stress gradients
T02: Comparison of international tunnelling contractsCarl Philipp FRIEDINGER (1), Klaus MITTEREGGER (2), Philip SANDER (1,3)1: University der Bundeswehr Munich, Neubiberg, Germany; 2: TIWAG-Tiroler Wasserkraft AG, Innsbruck, Austria; 3: RiskConsult GmbH, Innsbruck, AustriaProbabilistic Analysis of the Delivery Models Unit Price and Alliance applied at the Project Gemeinschaftskraftwerk Inn with Focus on the Construction Time1839 Innovative delivery models attempt to deliver major construction projects within budget and on time. However, proving their efficiency is difficult because of a missing base for comparing innovative and traditional delivery models. Therefore, a common ground is mandatory, as given in the “Gemeinschaftskraftwerk Inn” (GKI). Part of the GKI is a 23.5 km long headrace tunnel. The excavations started in the design-bid-build model with a unit price contract, which was terminated during construction by mutual agreement. The alliance contract was chosen to continue the tunnel advance with a new contractor. Only key personnel was exchanged. That allows a unique direct comparison of both delivery models. A probabilistic analysis was conducted. In principle, probabilistic models of the excavations were introduced to compare the construction time in the two different contract models. The key finding is that the construction time is 15 % to 22 % faster using the alliance delivery model. | alliance contract, Gemeinschaftskraftwerk Inn, innovative delivery models, probabilistic analysis, TIWAG alliancing contract
T13: Numerical methods in rock engineeringMohammad Youssef FALLAH SOLTANABAD (1), Amade POUYA (1), Lina Maria GUAYACAN CARRILLO (1), Laurent BROCHARD (1), Christophe DE LESQUEN (2), Minh-ngoc VU (2)1: Navier Laboratory/CERMES, École des Ponts ParisTech, Gustave Eiffel University, CNRS, Marne-la-Vallée, France; 2: Andra R&D, Châtenay-Malabry, FranceFluid injection influence on fracture propagation near an underground drift1842 This study analyzes the propagation of fractures around a gallery submitted to fluid injection. After recalling some concepts of fracture modeling in a porous medium, 2D simulations are carried out with the finite element code Disroc®. These simulations account for the anisotropy of the in-situ stress state. The impact of hydro-mechanical couplings under the effect of fluid injection is addressed by three approaches of increasing complexity: 1- The pressure is assumed to act only in the existing fractures and in the tunnel with no coupling in the rock mass. 2- The pressure field is assumed stationary, obtained from an independent simulation, and used as an input for the mechanical calculation. 3- The transient flow of the fluid in the fracture and in the rock, mass is considered and coupled with the mechanics. A comparison of these approaches clarifies the various contributions of hydromechanical couplings on fracture propagation over different time horizons. | Fracture propagation, porous media, underground storage, numerical modeling (FEM), hydromechanical coupling, Cohesive zone model (CZM)
T08: Hydropower projects and damsJohannes KLEBERGER, Irmina PÖSCHL, Jonas WEILiC consulenten Ziviltechniker GesmbH, Austria275 m high Yusufeli arch dam – Geotechnical modelling during construction1843 The World’s highest double curved arch dam outside of China was recently completed near the town of Yusufeli in NE Turkey. The project was ordered, supervised and managed by the State Ministry of Hydraulic Works (DSI), and constructed by contractor LIMAK of Ankara. The implementation of the 275 m high dam necessitated the construction of almost 480 m high very steep cut-slopes in extreme terrain. The contractor decided early during his contract to perform a multi-staged site investigation and consequent 3D geotechnical modelling. Data from a large variety of SI methods, including detailed geological documentation of ~20km of tunnels and ~200,000m² excavated slopes were continuously integrated into this 3D geo model. Together with a co-operative approach between acting parties, an active project management and highly professional service providers, the flexible 3D model helped to effectively deal with the important geotechnical issues and complete this ultra-high dam project without significant delays. | 3D modelling, digital data base, steering tool, design and construction management
T04: Deep mining and tunnellingYousef GOLABCHI, Matthew A. PERRASYork University, CanadaComparison of regression and classification Machine Learning algorithms for determining excavation damage zones depths1847 During the construction of underground excavations, the development of excavation damage zones (EDZs) is a crucial factor in designing permeability-sensitive excavations, such as deep geological repositories for nuclear waste. In this study, regression and classification machine learning (ML) models were employed. Specifically, k-nearest neighbors (KNN) and multi-layer perceptron (MLP) were used for both models. The aim of the regression ML models was to predict the depth of damage based on the maximum tangential stress around the opening and the crack initiation (CI) threshold. In contrast, the classification ML models aimed to determine different EDZ zones using the same features. After comparing the ML models with each other and with the traditional regression approach, it was concluded that MLP outperforms KNN for both models. Moreover, MLP exhibits consistency with the traditional regression lines. Thus, MLP can be effectively utilized for regression in higher-dimension modeling with a greater number of features. | Excavation Damage Zones, Machine Learning, Regression, Classification, K-Nearest Neighbor, Multi-Layer Perceptron
T15: Rock and rock mass propertiesDimitrios KOTSANIS, Pavlos NOMIKOSNational Technical University of Athens, GreeceCorrelating uniaxial compression strength and static Young's modulus with Schmidt hardness for prasinites1849 The scope of this study is to investigate the potential correlation of the Schmidt hammer rebound number with the uniaxial compressive strength and the static Young's modulus of prasinites, a metabasic petrological type outcropping in Attica Peninsula, Greece. Research works of similar content require the direct determination of the mechanical properties under consideration, so sixteen samples of NX diameter were prepared and examined in the laboratory. Then, the interpretation of the results revealed the relationship between the Schmidt hammer rebound hardness with the uniaxial compressive strength and the static Young's modulus of the studied rock materials. The derived empirical equations can provide valuable information for this rock type and can be used for preliminary investigations, at least in the study region. | Schmidt hardness, Uniaxial compressive strength, Static Young's modulus, Prasinites
T01: Challenging rock engineering projectsHanlim KIM (1), Gyeongjo MIN (1), Gyeonggyu KIM (1), Youngjun KIM (1), Jusuk YANG (2), Kyungjae YUN (2), Sangho CHO (1)1: Jeonbuk National University, Korea, Jeonju, South Korea; 2: Agency for Defense Development, Daejeon, South KoreaA method for investigating dynamic direct shear behavior of artificial jointed rocks using CNS direct shear box and Long Bar Drop Impact (LBDI) System1857 Understanding the shear behavior of a discontinuity in rock masses is vital for the proper design and construction of underground structures, considering their structural stability and cost efficiency. A static-based shear behavior is generally considered for designing these structures; however, rocks often undergo dynamic loading, such as seismic, blast, and percussive loading. Various studies have reported that rocks exhibit significantly different mechanical behaviors under dynamic loading, and frictional behavior may also exhibit different behaviors. In this study, a direct shear box and Long Bar Drop Impact (LBDI) apparatus were utilized to examine the dynamic joint shear behavior of artificially jointed rocks. Various dynamic loadings and initial normal stresses under constant normal stiffness (CNS) were considered in the experiment. The experimental results revealed that the dynamic joint shear strength depended on the initial normal stress and joint roughness. | Long bar drop impact (LBDI) apparatus, Direct shear box, Constant Normal Stiffness (CNS) condition, Dynamic joint shear behavior, Artificial jointed specimen
T08: Hydropower projects and damsYavar JALILI KASHTIBAN (1), Ali SAEIDI (1), Marie-Isabelle FARINAS (1), Javier PATARROYO (2)1: University of Quebec at Chicoutimi, Canada; 2: Hydro-Quebec, CanadaEvaluation of the effect of rock surface irregularities on energy gradient in unlined dam spillways1859 Rock scouring downstream of dams has raised concerns for dam safety. To assess hydraulic erodibility, it is important to consider both geomechanical and hydraulic factors. Unlined spillways are typically created through controlled blasting, resulting in irregular rock surfaces. Previous studies have not comprehensively considered various geometrical parameters, including joint opening, joint spacing, and surface irregularities, and their impact on hydraulic parameters. This study aims to investigate the influence of surface irregularities in 25 different configurations on hydraulic parameters. The findings will contribute to improving the current equation for the hydraulic erosive parameter in future research. ANSYS-Fluent CFD simulations were performed to analyze the determined unlined spillway geometries. Results showed that increased irregularity height reduced maximum velocity and energy, but led to increased total head loss and rock mass erosion. Furthermore, the water-rock interface experienced three times higher energy loss compared to the water surface. | Rock mass, Geomechanics, Unlined spillways, Erodibility, CFD
T06: Geological investigation and characterizationCamila Broetto MILLI (1), Alberto Ferreira AMARAL (3), Ana Paula DAHER (2), Marcos NASCIMENTO (3), Silas Santos SALGADO (3), Daniel Chaves dos SANTOS (3)1: Universidade Federal de Ouro Preto, Ouro Preto, Brazil; 2: Universidade Federal de Minas Gerais, Belo Horizonte, Brazil; 3: DF+ Engenharia, Belo Horizonte, BrazilDiagnosis of bench stability conditions in an iron ore open pit in the Quadrilátero Ferrífero/Minas Gerais/Brazil1860 The Quadrilátero Ferrífero, an important mineral province located in the state of Minas Gerais/Brazil, is influential for its world class deposits of commodities, such as iron ore. As in any other excavation, it is fundamental to grant the necessary bench slope stability conditions for the operation of its open pits. In this scenario, this paper develops products that supports the primary part of the diagnosis and planning of mining conditions in an iron mine. Field mapping and geological survey allowed gather structural data that supports geotechnical zoning of current slopes; kinematic analysis considering geometric conditions and the definition of potential types of failure mechanisms. This provided the overview of planar, wedge and flexural toppling occurrences in specific regions of the current operation. Corrective measures and geometric recommendations are discussed, as solution to ensure the stability of the structures and maintaining the production of this important commodity. | Slope Stability, Bench Analysis, Types of Failure, Quadrilátero Ferrífero
T01: Challenging rock engineering projectsAlfio DI GIOVANNI, Carmine TODARO, Simone SALTARIN, Marilena CARDUPolitecnico di Torino, Turin, ItalyThe phenomenon of tools' wear in a marble quarry: laboratory tests to evaluate the performance of conditioning as a wear preventer1861 Exploitation with a chain saw cutting machine has been the ordinary industrial practice in marble excavation for over thirty years, due to its ability to adapt to difficult environments and to guarantee a high level of safety during the cutting phase. Nevertheless, the presence of impurities in the calcite matrix, e.g. quartz, leads to the problem of rapid and unusual wear on cutting tools. In this study, two laboratory tests were selected and carried out to estimate the rock's wear potential: the CERCHAR Abrasivity test and the Soil Abrasion Test Apparatus (SATA). The results highlight a high degree of abrasivity in dry conditions, which was satisfactorily reduced by using water and additives. This mixture, typically used in tunnelling applications, is intended to decrease the wear from rock excavation and a significant reduction of this phenomenon has been noticed. | dimension stone exploitation, tool wear, Soil Abrasion Test Apparatus, CERCHAR Abrasivity test, wear reduction
T06: Geological investigation and characterizationMartin ZIEGLER (1,4), Markus FURCHE (2), Thies BEILECKE (2), Thomas BURSCHIL (2), Anne OBERMANN (3), Qinghua LEI (4), Chenxi ZHAO (4), Simon LOEW (4)1: Swiss Federal Office of Topography (swisstopo); 2: German Federal Institute for Geosciences and Natural Resources (BGR); 3: Swiss Seismological Service (SED); 4: Department of Earth Sciences, ETH Zurich (ETHZ)Monitoring damage evolution in a tectonically faulted clay shale — an experiment of the Mont Terri URL1866 The Progressive Failure (PF) project explores experimentally and numerically structurally-controlled damage evolution in faulted Opalinus Clay shale at 1:5 scale in the Mont Terri URL, Switzerland. The in-situ experiment consists of a central, large-diameter experiment borehole (representing a repository drift) and six monitoring boreholes. The experiment borehole intersects tectonic fault planes and a major fault zone; its air humidity is controlled to simulate open and closed drift phases. The rock mass damage evolution is recorded by manifold techniques, including borehole photogrammetry, active seismic and electrical resistivity tomographies, and recordings of pico-seismicity, aiming at detecting and observing damage initiation and evolution around the borehole. A discontinuum numerical model is built to mimic the tectonic fractures explicitly and investigate the damage evolution around the experiment borehole. This paper provides an introduction to the experiment and highlights key datasets collected over the first two years of the project. | structurally-controlled failure, Opalinus Clay shale, in-situ experiment, electrical and seismic tomography, borehole photogrammetry, numerical discontinuum simulation
T05: Digitalization & AutomatisationJosephine MORGENROTH (1), Jim HAZZARD (2), Shelby YEE (1), Davide ELMO (3)1: RockMass Technologies, Toronto, Canada; 2: Itasca Consulting Group, Inc., Minneapolis, USA; 3: The University of British Columbia, Vancouver, CanadaGeneration of a Discrete Fracture Network from digital discontinuity data captured using the 3D Axis Mapping method1867 Accurate mapping of geological structures and their orientations is a crucial step for analysis of underground excavation stability. A case is presented of a novel digital mapping workflow for generating a discrete fracture network (DFN) model. The RockMass Eon applies the 3-Dimensial Axis Mapping (3DAM) method to capture orientations and locations of discontinuities, producing a statistical distribution of their natural variability. The Eon uses infrared LiDAR and an altitude heading reference system to capture a point cloud, and a clustering algorithm is applied to extract statistically significant orientations representing the discontinuities. In this case study, 83 measurements are generated for 12 structures to provide a statistical dataset of the discontinuities. The mapped data from Glencore Kidd Operations in Canada are imported into ITASCA software to generate a DFN. This paper demonstrates that the use of digital data collection can streamline analyses and increase model confidence in underground rock engineering. | digital mapping, Discrete Fracture Network, numerical modelling, digitalization
T06: Geological investigation and characterizationGabriela Buitrago FRAINZ, Gustavo Vinicius GOUVEIAVale, BrazilGeotechnical parameters prediction from geophysical logging data using supervised learning methods1869 Rotary percussion drilling, despite being more agile and economical, does not provide the recovery of intact material as in traditional methods. With the use of this type of drilling, obtaining geotechnical parameters from alternative methodologies, such as geophysical logging, becomes of fundamental importance. Currently, however, geophysical logging does not meet the need to describe cores obtained by conventional drilling, due to methodologies established for geotechnics are based on tactile-visual parameters. Therefore, an opportunity is identified in the application of machine learning algorithms that use different data sources to obtain geotechnical parameters. Three algorithms were applied to the data sources and the scores varied depending on the comparisons and the acceptance criteria. It was observed that when the adjustment sequence is made in a more flexible criteria of acceptance, high levels of accuracy are achieved, which makes this tool practicable in geotechnical projects. | Machine Leaning, Geophysical, Geotechnical Logging, Mining, Supervised Learning
T07: Geological risks and natural hazardsHyung-Mok KIM (1), Yashwanth Kumar GUJJALA (1,2), Junya INOUE (3), Dong-Woo RYU (4)1: Sejong University, South Korea; 2: Indian Institute of Technology (Indian School of Mines), India; 3: The University of Tokyo, Japan; 4: Korea Institute of Geoscience and Mineral Resources, South KoreaAn improved calibration and uncertainty analysis for a ground subsidence using physics-informed neural network (PINN) approach1870 Accurately estimating surface settlement requires assessing under-bed layer properties. However, limited information necessitates the use of computational methods to address uncertainties. Recent advancements in machine learning and physics informed neural networks (PINN) have allowed researchers to incorporate physics into neural network models, enabling the forecasting of necessary parameters using inverse analysis algorithms. In this study, we employ the PINN approach to estimate unknown parameters associated with under-lying clay layer thickness and consolidation-aided material constants in an offshore vicinity of a river delta area. We implemented and compared Mikasa's one-dimensional approach, and also compared the outcomes of PINN techniques with Terzaghi's one-dimensional analytical solution and PEST back analysis. Additionally, our work introduces a methodology that utilizes PINN to identify these attributes and explores potential future applications of this framework. | PINN, Consolidation, Subsidence, Uncertainty
T01: Challenging rock engineering projectsAndreas GORICKI (1), Vipin PARIHAR (2)1: 3G Gruppe Geotechnik Graz ZT GmbH, Austria; 2: Afcons Infrastructure Limited, IndiaPandoh Highway Tunnels in Indian Himalaya - a rock mechanical challenge in design and construction1872 The National Highway NH-21 in the Indian State of Himachal Pradesh is developed into a 4-lane divided dual carriageway. The road section between Chandigarh and Manali with a length of approximately 21 km is located in topographically very difficult terrain where the Beas River formed a deep and narrow canyon with high and steep rock slopes. The paper describes the challenges in the design and the construction of the EPC Contract for six tunnels with a total single bore length of approximately 20 km. This includes geological design, NATM excavation design and detailed structural design for the rock tunnels in different tectonic formations. The variable rock mass conditions in combination with the short lateral distance to the very steep canyon slopes resulted in demanding rock mass behaviour and various difficulties to be solved during excavations. | NATM, tunnel, design, construction
T13: Numerical methods in rock engineeringDonát M. TAKÁCS (1,2), Tamás FÜLÖP (1,2), Áron POZSÁR (1,2), Róbert KOVÁCS (1,2,3), Mátyás SZÜCS (1,2,3), Peter VÁN (1,2,3)1: Department of Energy Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, Hungary; 2: Montavid Thermodynamical Research Group, Budapest, Hungary; 3: Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Budapest, HungaryModelling time-dependent processes resulting from thermo-viscoelastic behaviour of rocks1873 In rock mechanics, various situations are known where one may need a viscoelastic – rather than elastic – modelling. Examples include laboratory cyclic loading experiments, the Anelastic Strain Recovery method for determining in situ stress, and a recent new such area is the gravitational effect of waves (seemingly small but actually considerably relevant mass rearrangements) around underground gravitational wave detectors. It is also known that temperature influences the mechanical processes through thermal expansion, modifying strains and displacements and inducing thermal stresses. In certain cases, heat conduction – which determines the distribution of temperature – must also be incorporated in the description. Modelling these aspects poses a serious challenge. We present a thermodynamically consistent framework with a viscoelastic material model that captures these complex, coupled phenomena in a unified way. Our corresponding self-developed numerical scheme is able to predict the aforementioned thermo-viscoelastic effects for various scenarios reliably, with low resource demand. | viscoelasticity, thermal effects, wave propagation, extended symplectic numerics
T01: Challenging rock engineering projectsJose Allan MAIA (1), Teofilo COSTA (1), Anderson FONINI (2), Felipe GOBBI (2), Ricardo MENEZES (2), Gonçalo SONAGLIO (2), Fabiano MADRID (2)1: Vale S.A., Brazil; 2: FGS Geotecnia, BrazilDesign Review of the Remediation Project of a Highly Weathered Open Pit Wall from a Closed Iron Ore Mine in Brazil1874 In the late 90s, the excavation of an open pit mine was initiated in the Iron Quadrangle, a rich iron ore region situated in southeast Brazil. During years of excavation and mining duties, but especially after reaching its maximum depth, many instabilities occurred in the north wall, which presents about 500 m height and overall slope inclination that fluctuates between 30° to 35°. In the 2010s, a Real Aperture Radar and a series of prisms distributed across this wall indicated a total displacement of about 65 cm in 120 days during severe rainstorms. More recently, in the 2020s, InSAR data have shown that the displacements are still occurring after many slope failures, especially during the rainy season. As a result, the extensive erosion process accelerated the wall unloading generating a net of several unstable surfaces (comprising millions of cubic meters) controlled by the regional structural setting. Thus, during the design review of the remediation project, according to the reduced data available, several analyses were conducted to confirm the geotechnical parameters obtained from field and lab tests and assess the failure depth from back analyses. Finally, the design review service shows that the remediation proposed by the basic design could no longer address effective treatments for the decommissioning design of the north wall, but the remediation actions are still valid. | Decommissioning, Surface mining, Design review, Complex geology, Tropical environment, Weak rocks
T15: Rock and rock mass propertiesMaximiliano R. VERGARA (1,2,3)1: Skava consulting SA, Providencia, Chile; 2: Skava consulting ZT, Salzburg, Austria; 3: Institute of Soil Mechanics and Rock Mechanics (IBF), Karlsruhe Institute of Technology (KIT), Karlsruhe, GermanyComparison of conventional and cyclic oedometer swelling tests on rock specimens1878 The swelling behavior of rocks can be significantly affected by variations in moisture history, particularly through cyclic wetting and drying. The oedometer swelling test is widely utilized to assess the swelling characteristics of rock specimens. In this study, a comparison was made between conventional oedometer swelling tests and cyclic wetting and drying oedometer swelling tests on rock specimens. The objective was to evaluate the influence of cyclic wetting and drying on the resulting swelling curve. The slope of the swelling curve obtained from the cyclic test was more than double that of the conventional test. This comparison underscores the importance of accounting for cyclic wetting and drying conditions when assessing the swelling behavior of rocks and highlights the potential implications for long-term engineering projects involving rock structures. | Cyclic swelling, Rock swelling, Oedometer swelling test, Opalinus Clay
T05: Digitalization & AutomatisationNaval SINGH (1), Oscar LUNDHEDE (2)1: ORCX AB, FORCIT Explosives, Gothenburg, Sweden; 2: L-Consulting, B&R Sverige, Orebro, SwedenThe autonomous system cycle approach in off-road industrial applications – a holistic view1880 The fundamental need in ‘Off-road industrial applications’, e.g., mining, tunnelling, construction sites etc. are – safety, reliability, operational / economic viability, and sustainability. Available ‘automation and autonomous technologies’ has numerous benefits in off-road industrial applications. In the last 15 to 20 years ‘the automation and autonomous technologies’ has gained popularity in off-road industrial applications and addresses many of its above-mentioned fundamental needs. Although with all its operational and long-term economic benefits, still spread of automation and autonomous technologies are limited to few geographies and certain applications only. In this paper, we are presenting ‘the autonomous system cycle approach in off-road industrial applications’, and its potential benefits. We will also briefly review the available autonomous technologies, its status, and applications e.g., in mineral exploration, rock breaking, material haulage, rock processing etc. Through ‘the autonomous system cycle approach’, goal of this paper is to present a step-by-step guideline for integration and implementation of the new technologies in off-road industries. | Automation, Mining, Construction, Civil, Digitalization, Tunneling
T10: MonitoringMartin ZIEGLER (1), Simon LOEW (1), Arash Alimardani LAVASAN (2), Ernando SARAIVA (3)1: Department of Earth Sciences, ETH Zurich, Switzerland; 2: Faculty of Civil and Environmental Engineering, Ruhr-Universität Bochum, Germany; 3: Swiss Federal Nuclear Safety InspectorateMonitoring long-term hydromechanical processes in swellable Opalinus Clay shale of the new Belchen tunnel (Switzerland)1881 High swelling pressures and heaves of anhydrite-rich marls and Opalinus Clay shale (OPA) caused substantial damage to the Belchen highway tunnels between Basel and Lucerne in Switzerland, excavated with drill-and-blast technique in the 1960s. The tubes have to be refurbished and a new tunnel tube was constructed with a tunnel boring machine between 2016 and 2018. We have installed a monitoring system in a section of OPA to explore the evolution of radial pressures on the tunnel lining and the local hydro-mechanical conditions with the aim to characterize swelling processes of OPA in-situ. For the interpretation of radial pressures, the mechanical properties of the annular gap grout were explored and the impact of thermal strains on measured radial stresses was investigated with numerical simulations. Here we discuss key results obtained from the new Belchen tunnel that can be also relevant for design considerations of nuclear waste repositories in clay rocks. | Rock swelling, In-situ experiment, Swiss Jura mountains, THM coupled processes
T01: Challenging rock engineering projectsRaphael Perpetuo SOARES, Joao Pedro AMARAL, Gerson Rincon RIBEIROAngloGold Ashanti, BrazilGeotechnical Stope Index1883 The Geotechnical Stope Index aims to highlight the ore's dilution potential. The profile uses calculations to consider historical observations and geotechnical data analysis to identify potential geotechnical hazards about overbreaks in sublevel stoping. After each step, a column called "Estimated Dilution" is added to compare previous estimations with actual results, using a reconciliation method to calibrate the system's predictability feature. The Stope Index input limits have been calibrated based on stope performance data to provide realistic dilution estimations. This suggests that the system is being used in a mining or excavation context to estimate the amount of material that is lost or mixed in with the extracted ore during the mining process. By comparing the estimated dilution with the actual dilution, the system can improve its accuracy over time and provide more reliable estimates. This system is the geotechnical risk inserted in the mining plan before the mining production sequencing. | Stope Index, dilution, mine planning, geotechnical classification
T08: Hydropower projects and damsMarie-Hélène WISSE (1), Ali SAEIDI (1), Marco QUIRION (2)1: Université du Québec à Chicoutimi, Canada; 2: Hydro-QuébecExperimental study of joint opening and block protrusion effects on rock mass erosion in unlined spillways1884 Rock mass erosion in dams’ spillways can cause damages to the spillway structure and result in expensive repairs. In order to study rock mass characteristics having an effect on rock mass erosion in unlined spillways, a scaled physical model of a real dam spillway was built in a laboratory of Université du Québec à Chicoutimi. This physical model also allows studying the hydraulic parameters of the flow which have an effect on rock mass erosion. Some tests were undertaken to study the effects of joint opening and block protrusion on the hydraulic parameters in the simulated rock joints. The distribution of water pressure was measured on the faces of an instrumented block. The results obtained show that the main force having an effect on the block uplift is the water force acting on the top of the block. This force is mostly affected by protrusion configuration. | Physical model, Spillway, Rock Mass, Erosion
T04: Deep mining and tunnellingPengxuan JI (1), Qianbing ZHANG (1), Gisela VIEGAS (2)1: Monash University, Melbourne, Australia; 2: Newcrest Mining Limited, Melbourne, AustraliaMechanical and fracturing characteristics of defected cement mortar samples under biaxial confinements1887 In this study, quasi-static biaxial compression tests are conducted on rock-like cement mortar materials to examine the effect of shape, orientation, and interaction of pre-existing defects representing the rock mass with fissures created by nature or hydrofracturing. The mechanical and fracturing characteristics are investigated by stress-strain response, acoustic emission, digital image correlation and synchrotron X-ray computed tomography techniques. Results show the biaxial compression strength (σ_BCS) increases with confinement and restricts the development of cracks compared to uniaxial tests. In terms of hole samples, the confinement squeezes the tensile stress concentration area at the crown and invert of the hole. The orientation of the flaw impacts the failure characteristics and σ_BCS reaches its lowest value when the inclination angle is 45 degrees. The proposed integrated analysis framework is proven to be feasible for samples with more complicated geometry and the findings would benefit underground civil and resource-related projects. | Biaxial compression, Cement mortar, Pre-existing defect, Fracturing characteristic, Integrated analysis framework, Analytical solution
T04: Deep mining and tunnellingArpan NANDY, K Seshagiri RAO, Tanusree CHAKRABORTYIndian Institute of Technology Delhi, IndiaDevelopment of failure criterion for extensile fracturing of Kannur limestone under triaxial stresses1888 The classic rock mechanics is limited to evenly fractured rock mass at shallow depths wherein works of Mohr, Coulomb, Hoek and Brown, Drucker-Prager, Wiebols and Cook and more consider isotropic structural effects of joints seen at shallow depths. However, hardly any failure criterion is applicable to massive rocks available at deep depths. At deep tunnels, as one moves from the excavation surface into the rock, the fracture mechanism changes from extensional to shear cracking. The representative Kannur limestone is observed to exhibit exquisite extensile fractures as columnar shards are blown away in a manner much similar to strainburst in deep tunnels. The aim of the paper is to discuss the confinement dependency of limestone when subjected to triaxial stresses. Also, an improvement is suggested to Mogi criterion. This will further help to decide upon the multistep unloading of confining pressure observed during an excavation process in tunnels. | Brittle, triaxial, extensile, principal stress, crack
T10: MonitoringCharlotte WOLFF (1), Tiggi CHOANJI (1), Marc-Henri DERRON (1), Li FEI (1), Michel JABOYEDOFF (1), Andrea PEDRAZZINI (2), Carlo RIVOLTA (3)1: ISTE - University of Lausanne, Lausanne, Switzerland; 2: Sezione forestale- Repubblica e Cantone Ticino, Bellinzona, Switzerland; 3: Ellegi Srl - operational and administrative headquarters, Milano, ItalyUse of combined monitoring remote sensing techniques for the study of active fractures in a remote area: Case of Cima Del Simano rockslide1892 Cima del Simano Mountain (Swiss Alps) presents one main open fracture and several smaller fractures. Satellite InSAR highlights downward movements. This instability is worthy to be studied since it represents a risk for the road and villages located at its foot. Nevertheless, this mountain is challenging to study because of its bad accessibility and the strong atmospheric effects on remote sensing techniques. The study combines remote sensing techniques to acquire a maximal amount of information on the potential rockfalls sources and slow deep-seated landslides. Those techniques are Lidar, satellite InSAR and Ground-Based InSAR (GB-InSAR). They are aimed at confirming failure scenarios, predicted based on structural analyses and field observations. Small toppling movements are detected as well as more long-term moving areas (few mm/year). We estimate the limits of those instabilities and their corresponding volume by applying the Slope Local Base Level (SLBL) method. | Rockslide, InSAR, LiDAR, monitoring, SLBL
T10: MonitoringTiggi CHOANJI (1,2), Li FEI (1), Charlotte WOLFF (1), Franck BOURRIER (3), Romain GAUCHER (4), Kan Jean KOUAMÉ (5), Marc-Henri DERRON (1), Michel JABOYEDOFF (1)1: Risk Group, ISTE, University of Lausanne, Geopolis – Quartier Mouline 1015 Lausanne, Switzerland; 2: Department of Geological Engineering, Islamic University of Riau, Pekanbaru Riau 28284, Indonesia; 3: Université Grenoble-Alpes, INRAE, ETNA, 38000 Grenoble, France; 4: Service Ingénierie, Département des Hautes-Alpes, Gap, Provence-Alpes-Côte d’Azur, France; 5: CURAT, Côte d’Ivoire, Bd. De l'Université, Université Félix HOUPHOUËT-BOIGNY d'Abidjan Cocody (Côte d'Ivoire)Rockfall simulation and identification their sources locations along Massive external crystalline in Alps zone using LiDAR and Panorama Images: Case of La Grave, France1893 Rockfall hazards are fundamental problems for roadway safety in hilly areas. Monitoring rockfall activity along the 17 km long road from Chambon to La Grave is necessary to assess frequency, return period, and magnitude of rockfall events. According to historical inventory, more than 15 rockfall occurred between 1999 and 2020. Therefore, annual LiDAR measurements, with a point density of 40 to 189 points/m2, and more than 10’000 images from high-resolution cameras are used for detecting and evaluating rockfalls. Based on comparisons between 2020 and 2021, three rockfall sources totalling 200 m3 have been identified. Rock stability is assessed by analysing topography to identify potential rockfall sources using slope angle distribution (SAD) analysis and overhanging slopes from point clouds. Then, the trajectory from each identified source was simulated and verified using historical rockfall data. Thus, this combination of techniques better identifies and predicts deposited rockfall and impacts on infrastructures. | Rockfall, LiDAR, Alpes, Rock stability
T10: MonitoringChristoph Martin MONSBERGER (1), Fabian BUCHMAYER (1), Werner LIENHART (1,2)1: ACI Monitoring GmbH, Austria; 2: Graz University of Technology, Institute of Engineering Geodesy and Measurement Systems, AustriaDistributed Fiber Optic Monitoring Systems in Tunneling: Implementation from research into practice1894 Structural monitoring in combination with reliable data interpretation is essential to understand the deformation behavior of the lining and finally, to guarantee safe construction and operation. Conventional techniques may involve limitations, either in the spatial or the temporal resolution and do not deliver the overall deformation behavior along the entire lining. Distributed fiber optic sensing (DFOS) has significantly evolved in recent years to monitor large scale civil infrastructure, with scientific sensing designs being realized within various research projects. The technology can be advantageous for in-situ tunnel monitoring since the distributed strain and temperature sensing feature delivers a complete picture of the linings’ structural deformation behavior without blind spots. This paper discusses numerous DFOS tunnel monitoring designs and realizations at different construction sites and demonstrates that fiber optic sensors have considerably developed and provide essential capabilities to extend the conventional, geotechnical monitoring toolkit. | Distributed fiber optic sensing, tunnel lining, field applications, deformation behavior, structural integrity monitoring
T04: Deep mining and tunnellingAtsushi SAINOKIKumamoto University, JapanNumerical modelling of induced seismicity considering metre-scale stress heterogeneity in a fault damage zone1895 It is of paramount importance to gain a better understanding of induced seismicity taking place in deep underground for sustainable energy developments. Notwithstanding the effort made in the numerical simulation of induced seismicity, there is still a large gap between analysis results and field observations. The present study aims at simulating spatially and temporally distributed fault-slip events whilst considering metre-scale stress heterogeneity. The result indicates that the heterogeneous fault confining stress is crucial in the occurrence of fault-slip. The analysis of b-values computed from multiple seismic events simulated on the fault plane demonstrated that the b-value decreases with the reduction of the effective normal stress, showing consistency with the characteristic of induced seismicity in the field. This implies the possibility of applying the simulation method developed in this study to the risk evaluation for seismic hazards through the b-value analysis based on the advanced fault-slip modelling approach. | Induced-seismicity, stress heterogeneity, b-value, dynamic analysis
T14: Petroleum engineering and carbon sequestrationHuiwen PANG (1), Hanqing WANG (2), Yan JIN (1)1: China University of Petroleum-Beijing; 2: Petroleum Exploration and Production Research Institute, SINOPEC, People's Republic of ChinaPrediction of Safe Mud Window Based on Seismic Data in Carbonate Formation1896 To address the problem of predicting the safe mud window in China's TH oil field, we present a feasible seismic-based workflow that employs machine learning. Initially, multiple drilling fluid and mud loss engineering records were used to establish secure mud density windows for eight distinct wells with differing depths. Then, the well logs served as the link between drilling fluid density and through-well seismic data, and the relationship between drilling fluid density and seismic data was constructed using machine learning techniques involving ensemble learning. Finally, a 3D distribution model of safe drilling fluid density is generated, and its dependability is evaluated. The results of one validation well indicate that the model's complete blind test accuracy exceeds 75%. The model has a transverse resolution of 25 meters and a longitudinal resolution of 15 meters. It may offer theoretical guidance for devising drilling fluid density and wellbore construction. | Safe mud window, Seismic data, Machine learning, Carbonate formation
T13: Numerical methods in rock engineeringBijan PEIK (2), Andrew TSAI (3), Karl LAWRENCE (2), Karen MOFFITT (1)1: Equilibrium Mining Pty Ltd. (AU); 2: Equilibrium Mining Inc. (USA); 3: Equilibrium Mining Inc. (CA)Practical Implications of Using the Ubiquitous Joint Models in Continuum Applications1897 Failure mechanisms in open pit mining applications often involve a combination of weak rock mass and adverse structure. Major structure is typically included explicitly with less persistent fabric included using general anisotropy or ubiquitous joint constitutive models in both continuum and discontinuum applications. Implicit strength anisotropy in these constitutive models, however, is not equivalent to explicit jointed rock mass. This paper uses a conceptual slope example to illustrate that constitutive models incorporating ubiquitous joints exhibit an inherent strengthening which is considered a function of mesh density, mesh orientation, anisotropy orientation, and lateral constraint. The implication is an overestimate of the predicted stability margin by 5 – 10% or higher when key variables are compounded.  Key observations are summarized with the intent to provide the reader with a guide to using ubiquitous joint models. | Ubiquitous joint, Anisotropy, Numerical Modeling, Bedding, Slope Stability
T05: Digitalization & AutomatisationMasanari NAKATA (1), Karnallisa Desmy HALIM (1), Yeboon YUN (1), Harushige KUSUMI (1), Akinobu NISHIO (2)1: Kansai University, Osaka, Japan; 2: Kinki Regional Development Bureau, Osaka, JapanRock evaluation of NATM tunnel face using deep learning1899 Because of the complexity of the geological features, when the NATM method is used in Japan, the rock mass is evaluated in nine categories (A. condition of tunnel face, B. condition of excavation face, C. compressive rock strength, D. weathering and alteration, E. spacing of discontinuities, F. condition of discontinuities, G. direction of discontinuities, H. presence of water inflow, I. deterioration due to water) The evaluation is graded on four levels. The objective of this study is to use deep learning to quantitatively evaluate the frequency, condition, and morphology of fractures, as well as weathering and alteration of the tunnel faces; CNN was used to grade the three criteria regarding fractures. Furthermore, ratio of weathering area was detected by HSV color space for categories regarding weathering and alteration. We also applied Grad-CAM to verify whether the CNN model could actually evaluate rock fractures as a decision criterion. | New Austrian Tunneling Method, Rock mass rating, Convolutional neural network, Gradient-weighted class activation map
T13: Numerical methods in rock engineeringJosé G. GUTIÉRREZ-CH (1), Salvador SENENT (1), Eliana GRATEROL (1), Peng ZENG (2), Rafael JIMENEZ (1)1: E.T.S.I. de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, Madrid, Spain; 2: Chengdu University of Technology, ChinaApplicability of DEM - Rate Process Theory approach for rock creep simulation1902 One main long-term strength and safety concern in many geotechnical designs is rock creep response. Creep is the progressive deformation with time that many materials (soil, rocks, etc.) exhibit under an approximately constant stress. Based on laboratory and numerical results, several creep models (e.g., the Burgers Model) have been proposed; however, their main limitation is that the tertiary creep stage is often not well captured. To overcome this limitation, some progress has been made and new viscoelastic-viscoplastic creep models have been formulated. As an alternative, the Rate Process Theory (RPT) has recently been employed to successfully simulate all creep stages of rock samples. In this work, the Authors’ recent advances in this topic are used to illustrate the applicability of Discrete Element Method (DEM) modeling plus RPT to simulate rock creep, with particular attention to modelling of laboratory tests and rock creep in tunnels. | Discrete Element Method (DEM), Rate Process Theory (RPT), Rock creep, Tertiary creep
T13: Numerical methods in rock engineeringJosé G. GUTIÉRREZ-CH (1), Salvador SENENT (1), Svetlana MELENTIJEVIĆ (2), Rafael JIMENEZ (1)1: E.T.S.I. de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, Madrid, Spain; 2: Universidad Complutense de Madrid, SpainA new perspective of load-transfer behavior of rough rock-socketed piles1903 The response of axially loaded Rock-Socketed Piles (RSPs) has been extensively studied during the past. Most previous works focused on the behavior of smooth RSPs; however, our understanding is that the Load-Transfer Mechanism (LTM) of rough RSPs is still limited. Building on recent experimental and numerical works conducted by the Authors, this paper aims to provide new perspectives of the LTM of axially loaded rough RSPs. To do that, axially loaded rough RSPs are modelled with the Distinct Element Method (DEM) providing results that indicate that socket roughness is one of the crucial factors affecting the LTM of rough RSPs. Finally, the response of the mobilized axial load (with depth) and the corresponding mobilized shaft resistance, are presented and discussed. | Rock-Socketed Piles (RSPs), Distinct Element Method (DEM), Load-Transfer Mechanism (LTM), socket roughness
T06: Geological investigation and characterizationRamiro GARCÍA-LUNA, Salvador SENENT, Rafael JIMENEZE.T.S.I. de Caminos, Canales y Puertos, Universidad Politécnica de MadridApplications of the Structure from Motion photogrammetric technique to solve geotechnical problems at different scales1904 The Structure from Motion (SfM) photogrammetric technique has been widely used, due to its ease of use and low cost, as an excellent alternative for remote 3D rock mass characterization. This technique uses only the information obtained from the digital images acquired with a regular camera to generate very high-resolution 3D models. However, this technique is widely influenced by environmental and physical conditions (degree of luminosity, distance to the target, geometry, etc.) of each case. In this work, we present our previous experiences, from a micro-scale application (in the laboratory) for small-scale roughness analysis, to a large-scale application (in the field) for the characterization of long slopes using drones. For each application, different methodologies have been proposed, adapting the SfM technique and developing innovative solutions. The obtained results confirm the applicability of SfM to efficiently solve rock engineering problems at different scales and under different conditions. | Structure from Motion, photogrammetry, rock roughness, rock characterization, UAVs
T15: Rock and rock mass propertiesEsteban HORMAZABAL, Andrea RUSSOSRK Consulting Chile, ChilePractical estimation of veinlets shear strength properties in hypogene rock mass1908 Structures present in rock masses have a significant importance on strength and deformation of the rock mass that govern the rock mass’ performance in underground mining. Although important progress has been made in these last decades, data on their geomechanical properties is still limited. Furthermore, the majority of studies on joints characterization are connected to rock slopes, open structures and / or with soft infilling material, and low confinement stress conditions; while in underground hypogene rock mass, minor structures are generally sealed, with fillings not necessarily categorized as soft, and variable magnitude and orientation of the major stresses defined by the mining excavations sequences. This paper presents a practical approach to estimate the veinlets shear strength properties on hypogene rock mass based on rock mechanics tests results and Barton Bandis criterion, corresponding mainly to sealed veinlets with fillings with higher strength than those usually found in open pit mining. | Veinlet’s strength properties, rock mass characterization, Barton Bandis criterion
T01: Challenging rock engineering projectsThomas PILGERSTORFER (1), Katharina HOFER (2), Yvonne MONSBERGER (3), Jürgen VORINGER (4)1: Geoconsult ZT GmbH, Puch/Hallein, Austria; 2: ASFiNAG Bau Management GmbH, Ansfelden, Austria; 3: ASFiNAG Bau Management GmbH, Großwilfersdorf, Austria; 4: Swietelsky Tunnelbau GmbH & CO KG, Salzburg, AustriaBurgenland’s first tunnel takes its tribute – geotechnical retrospective of a tunnel collapse1909 The tunnel Rudersdorf, which is part of the S7 Fürstenfelder motorway is a two-lane twin tube road tunnel with seven cross passages, and has a length of approx. 1.785 m. The overburden of Burgenland’s first tunnel ranges between 2 and 72 m. Especially the excavation works in the northern tube were accompanied by several geotechnical challenges, which required an adaption of the excavation concept and the support measures. In the subsequently excavated southern tube, situated in similar geological and geotechnical conditions, a collapse of the tunnel occurred after about 100 m of tunnel advance with a material ingress of approx. 1.600 m³. The paper discusses the rock mechanical processes which led to the collapse on the basis of the evaluation of monitoring data, the observed system behavior before the collapse, the observations during the re-excavation works of the collapsed tunnel section, and the encountered geological and geotechnical conditions. | NATM, shallow tunnel, system behaviour, geotechnical monitoring, tunnel collapse
T06: Geological investigation and characterizationChao ZHANG, Wei WUNanyang Technological University, SingaporeSmart detection of limestone cavities in dense urban cities1910 Undetected cavities pose a great threat to underground construction in the limestone formations. In dense urban areas, additional challenges exist, such as fast and unnoisy field operations. Here we reported a new method to extract the characteristic energy of scattered and reflected signals for detection of limestone cavities. Comparing to the traditional seismic methods, this method does not require the seismic inversion and can thus achieve nearly real-time detection. The scattered and reflected signals are used to derive an anomaly score based on a signal processing framework, including multi-scale division and selection as well as enhanced low-rank feature extraction, to quantify possible locations of limestone cavities. We conducted a cavity detection test and demonstrated accurate detection of the horizontal location of a limestone cavity, but the accuracy of vertical location relies on the P-wave velocities of geologic layers. | Seismic imaging, limestone cavities, urban environment, field validation