ISRM 2023 - PUBLICATIONS

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 MineWater 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
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 rocksHydraulic 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
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 approachThe 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
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 LoadingWe 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 simulationThe 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
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 codeAt 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
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 IndonesiaThis 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
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 ClaystoneThis 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 RockThe 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
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 simulationDuring 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 strengthBord 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
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 analysisRainfall-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
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 excavationSimplified 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
T13: Numerical methods in rock engineeringTimo SAKSALATampere University, Tampere, FinlandNumerical prediction of thermal weakening effects on granite rockThis 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
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 influenceRock 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 optimizationMost 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
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 MineJwaneng 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
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 excavationsThorough 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
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 miningChuquicamata, 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
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 samplesThis 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 inversionRecently, 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
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 modelIn 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
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 DamThis 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
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 zoneThe 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
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 modelThe 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 estimationEstimating 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
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 3DECThis 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 miningSignificant 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
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 geometryIn 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
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 DesignAt 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
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 KoreaRoadheaders 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 dataIn 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
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 methodThe 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
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 fractureFluid 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
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 ClaystoneTunnelling 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
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 designThe 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
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-FLACGeological 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
T13: Numerical methods in rock engineeringGerold LENZiC consulenten ZT GesmbH, AustriaExcavation stability of deep tunnels in water-bearing fault zonesGroundwater 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
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 quartzThis 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
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)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
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 modelingConfinement 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
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 failureIn 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
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 algorithmThe 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
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 loadsA 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
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 5This 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
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 minesThis 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
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 AnalysisOwing 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
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 approachOne 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
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 rocksThis 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
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 dataFracture 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
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 ModelingExcavation-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
T13: Numerical methods in rock engineeringNicholas Ryland BARTONNB&A, NorwayGSI or JRC – continuum or discontinuum modelling – some suggestions and some critiqueGSI 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
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 stabilityIn 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 rocksIn 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
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 modelsPseudo-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
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 jointThe 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
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 impedanceShear 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)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
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 massThere 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
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 methodFatigue 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
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 MethodHydraulic 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
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 analysisA 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
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)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
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 costsThere 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
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 modelA 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
T13: Numerical methods in rock engineeringYasuhisa AONO, Tetsuo OKUNOShimizu Corporation, JapanData Assimilation for Prediction of Surrounding Rock Mass Behavior during Underground Structure Construction PhasesTo 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
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 cavitiesWallonia 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
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 massRock 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
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 massesThe 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 mineSeam 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
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 closureAt 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
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 conditionsThis 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
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 flowsDense 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
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 SandstoneWhile 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
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 BasinHighly 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
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 repositoriesIn 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 massThis 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
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 driftThis 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)
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 rocksIn 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
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 ApplicationsFailure 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
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 simulationOne 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 pilesThe 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