ISRM 2023 - PUBLICATIONS

T06: Geological investigation and characterizationAletta Gertruida HARTZENBERG (1), Daniel Francois MALAN (2)1: SRK Consulting, Canada; 2: University of Pretoria, South AfricaStructural mechanisms contributing to large-scale hangingwall instabilities on the UG2 reef horizonThe platinum mines in the Bushveld Complex of South Africa are characterized by a structurally complex rock mass. The mining activities in the narrow hard rock reefs are labour intensive with manual drilling, blasting, and cleaning methods. The underground personnel operate near the mining face where there is an increased risk of falls of ground. The presence of geologic structures in the stopes contributes towards hangingwall and pillar instabilities. The resulting falls of ground and large collapses may result in fatalities, significant ore reserve write-offs and even mine closure. Weak clay-like (alteration) zones contribute to these instabilities but are typically overlooked by mining personnel as it is not commonly encountered, and it is therefore not identified as a hazard. This paper summarizes the findings from case studies that investigated the impact of these structures, as well as suitable remedial strategies that may significantly reduce the risk of instabilities and improve mining safety at these operations. | structural complexity, hangingwall instability, pillar instability, ground penetrating radar
T06: Geological investigation and characterizationScott KIEFFER, Qian LIUGraz University of Technology, AustriaBlock in Point Cloud Data (BLOCKinPCD): A digital characterization system for rock outcropsThe extraction of 3D block structure from a point cloud is a nontrivial but important task in rock engineering. Block in Point Cloud (BLOCKinPCD) is a novel processing system that converts the point cloud data of rock outcrops into 3D rock structure. The workflow and processing functions include: (1) spatially identifying and extracting the point clouds of each discontinuity set; (2) quantifying the geometric parameters of each set (orientation, spacing and persistence); (3) characterizing the in-situ block system by assembling the block-forming sets into discrete fracture network; (4) quantifying the volume distribution of the block system and (5) evaluating the stability of blocks intersecting the excavation surfaces. As shown herein, BLOCKinPCD has been successfully applied to outcrops exposed in rock slopes and tunnel excavations. | Remote measurement, point cloud, rock structure, block system
T06: Geological investigation and characterizationJorge TERRON-ALMENARA, Charlie C. LINorwegian University of Science and Technology (NTNU), Trondheim, NorwayPerformance of the empirical method with rock mass classification systems to derive optimal rock support design in poor rock mass conditionsThe empirical method has been traditionally used for the design of permanent rock support in hard rock tunnels. Engineering classification systems have typically assisted empirical design with the description and classification of rock masses, together with recommendation of permanent rock support. In this sense, rock mass classifications have generally performed well, including poor ground conditions. However, research and studies during the last decades together with recent case records have shown that there is room for improvement when the empirical classifications are utilized in poor ground conditions. Some of the mentioned limitations are addressed in this article, through the study of a database with more than one hundred case records of monitored tunnels with empirical support design and excavated in poor ground conditions. The results indicate that a convenient design approach in poor ground conditions should involve the study of the ground behavior in the more traditional empirical method. | Empirical method, rock mass classification, poor ground conditions, rock support, ground behavior
T06: Geological investigation and characterizationYasmin Nicole BYRNE, Robert WHITTLECambridge Insitu, United KingdomThe impact of rock strength on the measurement of shear modulus from cavity expansion testingThe cavity expansion test is frequently used to determine the shear stiffness of rock. When stiffness is derived from an unload/reload event (cycle) then the process is repeatable and will give consistent values that are unaffected by drilling disturbance. The simplest interpretation of rock stiffness data is to assume the cycle is a linear-elastic event. In practice the response of the rock mass can be complicated by tensile failure and the level of shear stress. If the tensile strength is overcome and failure occurs, fracture growth can give cycles of reducing stiffness, unrepresentative of the rock mass at the insitu state. Material showing shear failure is likely to give a non-linear reduction of stiffness with strain. This includes decomposed and weathered materials. If the material remains largely intact, increasing the applied stress level will often produce a stiffer response with a power law trend. | Pressuremeters, Shear Stiffness, Tensile Failure, Cavity Expansion
T06: Geological investigation and characterizationAbdelmadjid BENRABAH, Luis JORDA BORDEHORE, Salvador SENENT DOMINGUEZTechnical University of Madrid (Universidad Politécnica de Madrid), Madrid, SpainA review of the application of empirical methodologies for preliminary analysis of natural cavesGeomechanical classifications have been used for the analysis of tunnels and mines since the 1970's. The database generated is huge: all types of lithologies, countries and works. However, there are few studies on its application to caves. The geotechnical stability of natural and anthropic caves (troglodytes) is a very little studied subject and of vital importance from the point of view of safety: there are thousands of caves that can be visited in the world, as well as cave houses, cellars and underground hotels and restaurants. We propose a review of the application of empirical methodologies for analysis of natural and anthropic caves. Both rock mass classifications CGI and Q index are too conservative, even in some cases alarmist. Stable caves appear as transitional or even unstable in graphs (Q) and rock classes (CGI). | Cave Geomechanical Index (CGI), Scaled Span, Q index, Rock Mass Classification, troglodyte
T06: Geological investigation and characterizationGeorg H. ERHARTER (1,2), Tom F. HANSEN (1), Shengwen QI (3), Neil BAR (4), Thomas MARCHER (2)1: Norwegian Geotechnical Institute, Oslo, Norway; 2: Graz University of Technology, Institute of Rock Mechanics and Tunnelling, Graz, Austria; 3: Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Aademy of Sciences, Beijing, China; 4: Gecko Geotechnics, Cairns, AustraliaA 2023 perspective on Rock Mass Classification SystemsDozens of rock mass classification systems (RMCS) have been developed since the 1950s for applications like tunnelling, mining or rock slopes. The abundance of systems and ongoing discussions amongst scholars and practitioners are symptomatic of the complexity of the problem and show that the community has not converged to commonly accepted procedures. Based on an online survey, this study aims to give an overview of the international spread of RMCS in use. The survey shows that GSI, RMR and the Q-system are the dominating systems in the world for underground engineering- and slope-related applications and thus have managed to prove their practical applicability throughout up to five decades. Conversely, the survey highlights that almost no system developed in the past 25 years has become internationally accepted, thus raising the question of whether today's RMCS can still live up to technological and scientific standards in 2023? | Rock Mass Classification, Tunnelling, Slopes, Mining, World Map
T06: Geological investigation and characterizationCatherine DORÉ-OSSIPYAN (1,2), Jean SULEM (1), Michel BORNERT (1), Alexandre DIMANOV (2), Patrick AIMEDIEU (1), Vincent DE GREEF (2), Andrew KING (3)1: Laboratoire Navier, Ecole de Ponts Paristech, France; 2: Laboratoire de Mécanique des Solides, Institut Polytechnique de Paris, France; 3: Psiche beamline, Synchrotron Soleil, Saint Aubin, FranceMulti-scale analysis of a porous carbonate rock under triaxial conditionsThe formation and evolution of deformation bands in a carbonate rock with high porosity is investigated by performing in situ triaxial experiments with high-resolution synchrotron X-Ray Computed Tomography by placing a specifically designed testing device directly in the tomograph. The processing of images by Digital Volume Correlation techniques provides insight on the deformation modes of the samples for various loading conditions. In more porous specimens with a homogeneous microstructure, many subhorizontal compactant deformation bands sequentially initiate, propagate, widen and fully saturate the volume of the rock sample after a few percent of overall strain. This leads to a rather uniform compaction of the sample. In contrast, denser samples with a more heterogeneous microstructure exhibit discrete deformation bands, in limited number. These bands propagate and widen, leading to strong localization of the deformation which remains restricted to certain parts of the sample. | in situ triaxial test, compaction bands, carbonate rocks, Digital Volume Correlation
T06: Geological investigation and characterizationYusuke HIRATSUKA, Sou KUMAMOTO, Hajime YAMAMOTOTaisei Corporation, JapanDevelopment of "T-DrillPacker" measurement system for groundwater inflow rate and pressure in advanced boringLarge groundwater flow into the tunnel during construction of a mountain tunnel can cause crucial problems. It is therefore important to investigate the location, flowrate, and hydraulic pressure of the flow paths ahead of the tunnel face in advance to tunnel excavations. One of the effective ways to characterize the flow paths is measurement of flowrate and pressure in the advanced horizontal boreholes using a packer system. However, with the conventional method, it is often difficult to carry out the installation of packer systems due to the risks of borehole collapse and delay in the construction schedule caused by pulling out the drilling string before packer installation. Therefore, the authors have developed a new measurement system that can be installed packer without pulling out the drilling tools. This paper describes the concept of this system, and a result of its successful application to a mountain tunnel construction site. | NATM, Advanced boring, Groundwater inflow rate, Hydraulic pressure, Packer system
T06: Geological investigation and characterizationJ.C. GRESS (1), M. FERREIRA (1), R.M. FAURE (2)1: Hydrogéotechnique, Fontaines, France; 2: Ecole Nationale des Travaux Publics de l'Etat, Vaulx en Velin, FranceRelations between elastic waves speeds and densitiesFor civil engineers, working on rocks, it is important to understand how density varies in the rock mass volume. Direct in-situ measurements are not easy, because of very often coring difficulties. The in-situ measures of elastic waves speeds can be interesting, but we need strong correlations between speeds and rock densities. Many researchers have worked on the subject but none has given physical relationships explaining the relations they had observed. Working on Nafe and Drake empirical curves, it is possible first to find an empirical relationship between Poisson ratio and density. Then, will be presented physical relationships existing between these two types of speed and rock density. Based on them, a relationship between rock mass elastic modulus Emr and density will be proposed. And finally comparing it to the one given by Hoek, linking Emr and the Geological Strength Index GSI, a relationship between GSI and density will be deduced. | Waves, speeds, densities, elasticity, modulus
T06: Geological investigation and characterizationMaria Teresa CARRIERO (1), Anna Maria FERRERO (2), Maria Rita MIGLIAZZA (1), Battista TABONI (2), Gessica UMILI (2)1: Department of Structural, Geotechnical and Building Engineering, Polytechnic of Turin, Turin, Italy; 2: Department of Earth Sciences, University of Turin, Turin, ItalyRoughness measure of a large in situ discontinuity surface by non-contact surveyRoughness of rock joint surface plays a key role in the stability conditions of rock slopes and it is commonly assessed on small portions of the outcropping surface or laboratory samples. However, roughness is naturally dependent on the considered scale, the analyzed surface sector (surface heterogeneity), and the direction of measurement (surface anisotropy). Therefore, the scale effect, heterogeneity and anisotropy should be quantitatively assessed to understand their role in shear resistance variations. This paper describes the surveys carried out on an extensive natural discontinuity in a slope along the Elva Valley Road (Northwestern Italy) subject to frequent and intense instability phenomena. A digital surface model (DSM) of the entire surface was obtained through UAV (Unmanned Aerial Vehicle) photogrammetric technique and the resulting point cloud was analyzed in order to measure the spatial variability of the surface roughness considering the different directions and the surveying interval. | Roughness, scale effect, Morphology, Non-contact survey
T06: Geological investigation and characterizationMarkus KASPAR, D. Scott KIEFFER, Qian LIUGraz University of Technology, Graz, AustriaHolographic mixed reality: an enhanced technology for visualizing and evaluating complex 3D geologic dataRock mass characterization involves field data collection, processing, and analysis of the measurement results. Software packages facilitate creation of 3D models as well as the representation of rock mass parameters and resulting block arrays. The computer-generated imagery is traditionally illustrated as static perspective pseudo 3D screenshots, 2D maps or numerical tables and diagrams. Mixed reality greatly improves data visualization within an immersive and interactive 3D holographic environment enabling interaction with scaled holograms at the actual field dimension. The holograms are inspected individually or via remote collaboration within shared virtual spaces. The physical outcrop together with quantitative aspects of the rock mass structure is portrayed, enhancing communication and understanding of actual field attributes. This paper presents case examples of mixed reality holographic models based on photogrammetry, terrestrial and hand-held LiDAR devices. The benefits and potential applications of mixed reality in engineering geology and rock mass characterization are summarized. | Mixed reality, digitalization, rock mass characterization, hologram
T06: Geological investigation and characterizationDae-Sung CHEON (1), Seungbeom CHOI (2), Won-Kyong SONG (1)1: Korea Institute of Geoscience and Mineral Resources, Republic of Korea (South Korea); 2: Korea Atomic Energy Research Institute, Republic of Korea (South Korea)Key Parameters and Distribution in Rock Mechanics for HLW Site Selection in KoreaA step-by-step approach is being adopted worldwide with respect to site selection for the geological disposal of high-level radioactive waste (HLW). Korea also adopted a three-step approach. In order to conduct systematic and efficient site investigation and site evaluation, a classification system for evaluation elements by stage has been proposed, and it is subdivided into aspects, items, and parameters. Among a total of 17 items and 103 parameters, rock engineering-related items are 3 items and 33 evaluation parameters. Uniaxial compressive strength, in-situ stress are selected as key evaluation parameters, taking into account domestic and foreign cases, the importance of rock engineering, and the existence of international standard testing methods. Their characteristics and the distribution range of the domestic parameters are investigated. In this study, two types of granite were selected and regional distribution characteristics were analyzed based on the data obtained through drilling up to 750 m. | HLW, Site investigation, Key parameters, Distribution, Uniaxial compressive strength, In-situ stress
T06: Geological investigation and characterizationLeandro R. ALEJANO (1), Elena MARTÍN (1), Ignacio PÉREZ-REY (1), Brais X. CURRÁS-REFOJOS (2), Fco. Javier SÁNCHEZ-PALENCIA (2)1: University of Vigo, Spain; 2: CSIC-CCHS - Instituto de Historia, Madrid, SpainRoman gold exploitation at the archeological site of Las Médulas (NW-Spain) by means of Ruina Montium: a rock and fluid mechanics perspectiveLas Médulas is an area located in NW-Spain featuring a landscape environment formed by an old Roman gold mining operation. It is thought to be the largest open-pit gold mine in the Roman Empire and it was exploited during I and II centuries AD. The archaeological site and its environment were declared UNESCO World Heritage in 1997, based on its value as a cultural landscape. The most spectacular mining system used there was the one that Pliny the Elder called “Ruina Montium”, that is, "the collapse of the mountains". This technique was applied to reach in one go the conglomerate levels richer in gold (Santalla formation), removing a thick cover of conglomerate block-in-matrix (bimrock) type waste. Unfortunately, there are no obvious remains of this procedure. In this multidisciplinary study in progress, archaeologists and engineers work together to better understand the detailed process used by the Romans to cave the mountains. | Roman mining, archaeology, fluid mechanics, rock mechanics, collapse, bimrock
T06: Geological investigation and characterizationArthur D. DE ALWIS (1), Mehdi SERATI (1), Derek MARTIN (2), Arcady DYSKIN (3), Elena PASTERNAK (3), David J. WILLIAMS (1)1: The University of Queensland, Australia; 2: The University of Alberta, Canada; 3: The University of Western Australia, AustraliaAcoustic Emission Characteristics of Mode I Rock FracturingUnderstanding the propagation of Mode I fracture is crucial in rock mechanics since this fracture mode is the predominant cause of catastrophic failures in brittle rock-like solids. For investigating the mechanisms of rock fracturing, Acoustic Emission (AE) is a widely accepted tool. In this paper, various AE parameters, including the number of hits, source location, Rise Angle (RA), and Average Frequency (AF) are considered to evaluate the AE characteristics during Mode I loading-induced fracturing of basalt. Certain waveform features such as the dominant frequency and amplitude distribution are further investigated. Results suggest interesting findings in the changes in cumulative hits, source location, and RA at different stages of fracture. The observed trend in peak frequencies found in the study, in particular, points to promising future studies. | Mode I Rock Fracture, Acoustic Emission, Source Location, Rise Angle, Average Frequency, Dominant Frequency
T06: Geological investigation and characterizationHolger JUD (1), Dieter TRONICH (1), Gerd SIEBENBORN (2)1: Smoltczyk & Partner, Germany; 2: Wasserstraßen- und Schifffahrtsamt Elbe-NordseeStructural and Geotechnical Investigations for the Remediation of Jetties and Seawalls on HeligolandHeligoland is a German offshore island located about 50 km from the German coastline in the North Sea. Storm surges, especially in 1954, caused massive destruction and damage to the jetties and seawalls. Moreover, the "Big Bang" blast in 1947 as well as wartime bombardments lead to extensive rock fracturing. Due to these impacts the jetties and seawalls displayed serious structural deficiencies, such as differential settlements and potential instabilities. Against this background, a site investigation was carried out for the geotechnical design of the remedial measures. Special drilling rigs were used, equipped with an interchangeable drill head for both sonic and wireline drilling methods while incorporating an automatic drilling data acquisition system. This allowed high quality structural and rock cores and samples to be obtained in accordance with sampling and testing standards. | Investigation, Sonic drilling, automatic drilling data acquisition, geological modelling
T06: Geological investigation and characterizationNana KAMIYA, Weiren LINKyoto University, JapanOne-dimensional consolidation properties of sedimentary soft rocks from the Boso Peninsula, central Japan using a constant strain-rate loading systemConsolidation property is an indicator of load bearing capacity of foundation and also reflects the process of geological evolution. In general, consolidation test has been performed for soil materials in geotechnical area, however we tried to conduct consolidation test using Mio–Pleistocene sedimentary rocks taken from a forearc basin located at a subduction zone. Consolidation yield stress almost increased as porosity decreases, however consolidation yield stress has variation in same porosity and it was increased with depth of sampling point, that indicates the consolidation line of this setting and the consolidation yield stress would record the maximum burial depth of the basin. SEM images show the consolidation fabric which has layer structure and high-resolution X-ray CT images show a deformation during the consolidation test. | Sedimentary soft rock, consolidation test, consolidation yield stress, X-ray CT image
T06: Geological investigation and characterizationEdward Alan BUTTONARUP Pft. Ltd., AustraliaAssessing Intact Rock Properties for the Salang Highway Tunnel Upgrade Route Selection StudyThe current 2700m long Salang Tunnel at the time of completion was the highest road tunnel at 3400 m providing all-weather connectivity from northern Afghanistan to the southern regions and the capital Kabul. The Salang Corridor is a crucial link within the Central Asian Regional Economic Cooperation Program’s transportation network. The intact rock test results presented within this contribution are associated with work to identify and optimizing the central tunnel alignment to reduce the maximum elevation and optimize the road alignment. Eight boreholes were drilled between 150m and 220m depth to investigate the ground conditions and rock properties for three previously identified tunnel alignments, due to very poor ground conditions a 9th borehole was terminated at 42m depth. The results demonstrate that with appropriate sample selection and testing methods and procedures reliable and consistent data can be acquired to characterize and assess rock properties and associated tunnel hazards. | Rock testing, Brittle failure, Granite, Alpine Tunnelling
T06: Geological investigation and characterizationIrmina PÖSCHL (1), Walter FREI (2)1: iC consulenten ZT GmbH, Austria; 2: GeoExpert AG, SwitzerlandThe use of dynamic moduli logging in large-scale geotechnical modellingThe dynamic elasticity rock mass modulus was used as reference parameter for developing large-scale geotechnical models. Modulus values were derived from p- & s-wave seismic refraction surveys. Hybrid seismic surveying, an increasingly applied combination of refraction and reflection seismic testing, proved being a particularly helpful tool for delivering the data necessary for a comprehensive interpretation of modulus distribution. Seismic surveying provides large amounts of spatially continuous data coverage at relatively small cost and time effort. Due to the non-intrusive nature of probing, the recorded data type reflects in-situ conditions, not corrupted by invasive procedures. Adequately processed, the data can be directly transferred into digital models for visualization, evaluation and interpretation. The experiences made from survey programs with different investigation methods and targets opened new perspectives for rock mass characterization, but also disclosed limitations to be considered for a successful application. | Elasticity modulus, hybrid seismic surveying, seismic refraction tomography, reflection seismic surveying, 3D modelling
T06: Geological investigation and characterizationJose Antonio VALIDO GARCÍA (1), Luis Enrique HERNÁNDEZ GUTIÉRREZ (2,3), José Miguel CÁCERES ALVARADO (1), Carlos Javier PÉREZ GONZÁLEZ (4)1: Instituto Universitario de Materiales y Nanotecnología. Departamento de Ingeniería Industrial, Universidad de La Laguna, La Laguna, Spain; 2: Consejería de Obras Públicas, Transportes y Vivienda. Gobierno de Canarias, Santa Cruz de Tenerife, Spain; 3: Instituto Volcanológico de Canarias” (INVOLCAN), Tenerife, Canary Islands, Spain; 4: Departamento de Matemáticas, Estadística e Investigación Operativa, Universidad de La Laguna, La Laguna, SpainSimple and multiple regression study of physical-mechanical properties of ignimbritesThe objective of this study is to analyse the relationship between uniaxial compressive strength (UCS) with physical properties, such as apparent density (AD) and ultrasound velocity (PWV), and with other mechanical properties, such as point load test (PLT) and indirect tensile strength (BTS). This analysis was carried out on a group of ignimbrites, consisting of a total of 45 samples, from the Canary Islands and consisted of applying simple regression and multiple regression methods. Applying the simple regression method, it was determined that the ultrasound velocity (PWV) is the property that explains the variability of the compressive strength (UCS) to the greatest extent. Using the multiple regression method, a model capable of increasing the proportion of variability of the (UCS) is obtained, using the apparent density (AD), the ultrasound velocity (PWV) and the point load test (PLT) as independent variables. | Canary Island, ignimbrite, boreholes, geomechanical properties, regression
T06: Geological investigation and characterizationYong-Zhi HUANG, Tai-Tien WANG, Fu-Shu JENGDepartment of Civil Engineering, National Taiwan University, Taipei, TaiwanA study on point cloud interpretation of fracture intensity and its spatial variabilityIn geological surveys with a rock engineering focus, the investigation and description of discontinuities is an important but time-consuming and labor-intensive step. With advances in surveying and mapping technology, digital surface models (DSM) and their corresponding point clouds can reproduce the geometric properties of outcrops, and provide a useful intermediary for rock fracture investigations. Here we develop and apply a method for fracture mapping that employs a discontinuity set extractor (DSE) program to capture fracture planes from point clouds and a spherical scan approach to determine fracture intensity in a direction-dependent fashion. The proposed approach is applied to obtain the fracture intensity of six outcrops, and the spatial variation of fracture intensity and corresponding influencing factors are investigated accordingly. The fracture intensity has both heterogeneous and directional-dependent characteristics. Their variations are affected by lithology and folds. | Fracture intensity, Spatial variability, Advance surveying and mapping, Point cloud interpretation
T06: Geological investigation and characterizationMaria Lia NAPOLI (1), Lorenzo MILAN (1), Monica BARBERO (1), Edmund MEDLEY (2)1: Politecnico di Torino, Italy; 2: Terraphase Engineering, Oakland, CA, U.S.AApplication of the point counting technique for estimating the VBP of geotechnically complex formations (bimrocks/bimsoils)The estimation of the Volumetric Block Proportion (VBP) of geotechnically complex block-in-matrix formations (such as melanges) is crucially important for reliable predictions of their mechanical behavior, and for reducing safety risks and extra costs caused by unexpected technical problems that can occur during excavation/construction works. However, estimating site-scale VBPs is extremely difficult. This paper describes a statistical investigation of virtual block-in-matrix models to determine the amount of bias introduced when the point counting technique is used to infer VBPs from in-situ 0D (point) measurements (PBP). A graph is provided to obtain an uncertainty factor (UF) to adjust the measured PBPs to real VBPs, on the basis of the block content measured and the size of the area analyzed. To validate the approach, the results are compared to those provided recently by Napoli et al. (2020), where the uncertainty in estimates of VBPs from 2D measurements was investigated. | Bimrocks, bimsoils, point counting technique, volumetric block proportion (VBP), uncertainty factor, statistical analysis
T06: Geological investigation and characterizationGabor SOMODI (1), János BORSODY (2), Ágnes KRUPA (3), Krisztián PETRIK (1), Balázs VÁSÁRHELYI (1)1: Budapest University of Technology and Economics, Hungary; 2: Hidro-Duna Ltd.; 3: Mecsekérc Plc.Rock mass characterization during the construction of a twin-tube motorway tunnel in HungaryA twin-tube motorway tunnel has been under construction near Sopron in Hungary. Geological inhomogeneity during the excavation required the redesigning of the schedule and reorganisation of the project. The geological overbreaks and weak, unstable tunnel faces caused minor stability problems that could be handled locally, but did not substantially affect the planned support. The thick and hard conglomerate layers, harder than expected, caused a significant reduction in the speed of progress and justified the purchase of more powerful excavation tools. A wide tectonic zone appears in the form of several minor dislocations (0.1-1.5 m), characterising a complex strike-slip fault with persistent dislocations caused by minor normal and reverse faulting. This condition represented the most complicated part of both tunnels in terms of stability. Based on the face mapping information, indicator numbers were assigned to the geological layers and then GSI values were calculated using different equations. | weak rock, rock mass classification, calcareous sediment, local instabilities
T06: Geological investigation and characterizationHongkyu YOON, Jennifer HARDINGSandia National Laboratories, United States of AmericaPhysics-informed machine learning of flow and transport problemsRecent advances in machine learning/deep learning (ML/DL) methods show promising results to enhance our ability to develop fast surrogate models and estimate heterogeneous subsurface properties through inverse modeling approaches. In this work we explore physics-informed neural networks (PINNs) as a way to incorporate governing partial differential equations (PDEs) in the ML framework through loss functions. With advection-dispersion-reaction (ADR) and Darcy equations, PINN methods are evaluated for multiple cases by changing model parameters and the inverse modeling framework. This work demonstrates that PINNs tend to perform better than data-driven only model with less collocation points and the potential capability of PINNs for accurate surrogate models to coupled geomechanical problems in the subsurface. | Machine learning, Physics-informed neural network, Inverse modeling, Advection-dispersion-reaction
T06: Geological investigation and characterizationÅsa FRANSSONDepartment of Earth Sciences, University of Gothenburg, SwedenHydrogeology and grouting - a field experiment in shallow, crystalline rockWhen constructing a tunnel or a shaft in a fractured rock mass, the main water-bearing features are of major importance. A limited reduction in leakage, as well as a greater impact area, are potential consequences if these features are not considered in hydrogeological descriptions and in grouting design. This paper presents a grouting field experiment performed in a shallow, crystalline rock mass. An experiment where the spatial distribution of hydraulic conductivity (transmissivity) of water-bearing features was expected to show both directional dependence and connectivity. This was confirmed, grouting was performed, and hydraulic conductivity reduced. We expect that the demonstrated experimental work, highlighting general nature, pattern, and properties, can be used to improve hydrogeological descriptions and grouting design and form a basis for environmental impact assessments. Further, storage coefficient, and hydraulic aperture, based on transmissivity, can, potentially, be an additional indicator of fracture stiffness and situation of stress. | Hydrogeology, grouting, environmental impact, transmissivity, storage coefficient, fracture stiffness
T06: Geological investigation and characterizationDaniel PRADO AZEVEDO (1), Eduardo Antonio GOMES MARQUES (2)1: Universidade Federal do Pará, Brazil; 2: Universidade Federal de Viçosa, BrazilThe use of 3D digital implicit geological models on slope stability evaluationThis study highlights the importance of efficient and agile methods in geological-geotechnical evaluations for open pit mining. The use of 3D geological modeling technologies allows for a better understanding of lithological contacts and strength parameters, enabling the assessment of rock mass geometry and slope stability analyses. Implicit modeling software facilitates the creation of detailed geological-geotechnical models, which can be updated with new data. These models provide cross-sections for slope analysis and can simulate future mining progress and water level fluctuations. By utilizing these tools, the quality of evaluations improves, and areas requiring additional information are identified. The paper presents the results of an implicit geological-geotechnical model for an open pit mine and showcases a slope stability analysis conducted on a geological-geotechnical cross-section. Overall, these techniques enhance understanding, improve analyses, and contribute to more reliable open pit mine design. | Slope Stability, Stability Analysis, Softwares, Geotechnics, Implicit Model
T06: Geological investigation and characterizationAbhiram Kumar VERMA, Binay Kumar SAWIndian Institute of Technology Kharagpur, IndiaShear strength characterization of a natural rock joint developed in Peridotite depositsThe shear behavior of open rock joints in Peridotite rock, igneous in nature, is studied. These joints are open, random, with the most frequent aperture of 1-2 mm, filled with serpentinite, magnesite, chlorite, asbestos, and talk. Roughness are characterized as rough, smooth, undulating, planar, stepped, stepped/smooth plane, rough stepped, stepped undulating, polished, planer rough, and others. Direct shear test at three constant normal load are carried out, and joint characteristic curves are developed to determine their mechanical properties. All joint sample was collected from different boreholes of 75 mm diameter from depth ranging from 13.18 m to 555.78 m. Further, joints basic friction angle, JRC, JCS are determined. Based on these test results, the dilation and peak shear displacement models are developed and compared with existing shear strength models. | Open rock joint, CNL, Direct shear test, Dilation
T06: Geological investigation and characterizationHalil KUMSAR (1), Ömer AYDAN (2), Hitoshi MATSUBARA (2), Kouki MORI (2)1: Pamukkale University, Turkey; 2: University of the Ryukyus, JapanCharacteristics of hydro-magnesite of Salda Lake (Türkiye) and their implications on rocks of Jezerro Crater in MarsHydro-magnesite formation in Salda Lake in Türkiye receive great attention as an example on Earth in relation to the early life traces in the Jezerro Crater of Mars. The authors investigated Salda Lake and sampled hydro-magnesite. The sampled stromatolites vary newly formed soft ones to quite hardened ones. Microscopic structures and X-Ray analyses of samples were used to characterize the minerological constitutents. Some samples were prepared from large pieces of stromatolites to determine physico-mechanical properties. The investigation results are presented and the implications of the outcomes from these investigations on the characteristics of rocks in Jezerro Crater in Mars are discussed. | Salda Lake, hydro-magnesite, physico-mechanical properties, stromatolite, X-Ray analyses
T06: Geological investigation and characterizationErlend SKRETTING, Georg H. ERHARTER, Jessica Ka Yi CHIUNorwegian Geotechnical Institute (NGI), NorwayVirtual reality based uncertainty assessment of rock mass characterization of tunnel facesRock mass characterization has a high degree of uncertainty due to difficulties in capturing the heterogeneity of the rock mass, and due to human subjectivity and biases while mapping. Since classification systems are often used as a tool to decide rock support design, misinterpretation of the rock mass can lead to an inadequate support design. In this study, 3D-scans of tunnel faces are implemented in virtual reality (VR) to investigate the uncertainty of tunnel face mapping. A VR-mapping survey is conducted where 14 professional and experienced engineering geologists have performed Q-system based tunnel face mapping and the results allow to quantify the uncertainty related to that process, as well as investigating the different psychological aspects that influence engineering geologists in the mapping process. The paper closes with a discussion about what this VR-study's results mean with respect to rock mass classification and possible future applications for VR in rock engineering. | Rock mass characterization, tunnel face mapping, virtual reality (VR), rock mass classification systems, Q-system, uncertainty
T06: Geological investigation and characterizationMadelyn SUMNER, Laura PYRAK-NOLTEPurdue University, United States of AmericaVisualization of Fracture Intersections from 3D X-ray ImagingThough fracture intersections control the connectivity of a fracture network, few studies have examined the deformation of intersections. A laboratory study was performed to examine the effect of an applied stress on a fracture network and the intersection geometry. 3D printing was used to create 2 orthogonal intersecting fractures with either a “+” or “x” orientation relative to an applied vertical load. 3D X-ray microscopy was used to image the fracture network. For the “+” orientation, the network connectivity was maintained by the vertical fracture that did not deform significantly under load. However, for the “x” orientation, the void volume and connectivity between the two fractures decreased significantly and almost ceased to exist at the highest load as the topology transitioned from “X” to “Z” to “V”. Hydro-mechanical modeling of fracture networks may need to account for changes in intersection connectivity from perturbations in stress. | Fracture networks, fracture intersections, apertures, stress, imaging
T06: Geological investigation and characterizationMichelle PIENAAR (1), Raymond DURRHEIM (2), Musa MANZI (2), Glen NWAILA (2), Hennie GROBLER (3), Thabang KGARUME (4), Dean PRETORIUS (4), Michael VAN SCHOOR (4), Abrie OBERHOLSTER (5)1: Mandela Mining Precinct, South Africa; 2: University of the Witwatersrand, South Africa; 3: University of Johannesburg, South Africa; 4: CSIR, South Africa; 5: University of Pretoria, South AfricaMitigating the rock fall and rockburst risk in South African gold and platinum mines through advanced knowledge of the ore bodyThe Mandela Mining Precinct was launched in 2018 with the goal of modernizing the South African mining industry. It comprises three major initiatives that seek to improve efficiency, health and safety in current mining operations; develop fully mechanized systems to mine narrow tabular ore bodies in hard rock; and develop non-explosive rock-breaking systems. The crosscutting Advanced Orebody Knowledge (AOK) program seeks to develop technologies to characterize the rock mass ahead of mining and identify potentially hazardous geological features. Mining methods, layouts and rock support systems will be adjusted accordingly to mitigate the risk of rock falls and bursts. Technologies include rock drilling, light detection and ranging (LiDAR), ground penetrating radar (GPR), electrical resistance tomography (ERT), and various acoustic, thermographic and seismic techniques. Machine learning methods are being implemented to improve data processing and interpretation. This paper describes the status of the research program at 31 May 2023. | rock fall, rockburst, LiDAR, GPR, ERT, thermography, seismics
T06: Geological investigation and characterizationJunxiong YANG, Sebastian D. GOODFELLOW, John P. HARRISONUniversity of Toronto, Toronto, CanadaUsing borehole breakout data to constrain the in situ stress tensorKnowledge of the in situ stress state is critical for underground rock engineering projects, but direct measurement data are often not available. Although borehole breakouts are only indicative of the in situ stress state, they nevertheless represent a significant data resource. Properties such as breakout orientation, width and depth can all potentially be used to constrain the in situ stress state. In this paper, we present a novel global optimization and associated objective function that uses breakout data to constrain the normalized in situ stress tensor. This tensor is one in which the magnitudes of the three principal stresses are normalized with respect to the difference between the maximum and the minimum principal stresses, and three Tait–Bryan angles describe the principal stress orientations. The efficacy of the scheme is demonstrated by applying it to breakout data obtained from deep mining operations in the Sudbury mining district of Ontario, Canada. | borehole breakout, in situ stress, global optimization, normalized principal stresses, principal stress orientations
T06: Geological investigation and characterizationJayeeta DEY (1), Sujit ROY (1), Abdul MATIN (2)1: SRK Mining Services (India) Private Limited, Kolkata, India; 2: University of Calcutta, Kolkata, IndiaMapping of faults in underground mine by Sub Surface Profiling technologyUnderground mines often experience roof collapse due to the presence of faults. While major faults are identified during exploration, many a time smaller faults remain unidentified. Underground mine approaching such unidentified faults may result in sudden roof fall and groundwater ingress. To resolve the issue, we utilized GPR based Sub-Surface Profiling technology that is capable of capturing fault related deformation features as anomalies. Results of SSP scanning and its interpretation from an underground coal mine in India is presented. Signatures from SSP are found useful in mapping fracture frequency, identifying fault core and damage zone, and helped assessing the degree of cataclasis. Regular SSP scanning helped predicting the rock conditions in advancing galleries and facilitated to adopt appropriate roof and water management strategy beforehand. Considering the usefulness of the technology, it may be adopted in underground mines globally, particularly where fault related deformation pose challenge to roof management. | Underground-mine, fault, roof-collapse, Sub Surface Profiling, roof-management
T06: Geological investigation and characterizationJohannes HORNER (1), Jennifer Andrea BETANCOURT (2)1: recon-struct geologic consulting GmbH, Hallein, Austria; 2: Geologist, Bogotá, ColombiaUnderstanding the geological and geotechnical drill core logging process – key to successThe preparation of a consistent ground model in mining and civil construction requires a clear understanding of the geological and geotechnical data collected during the different investigation phases. Drill core logging data may be collected during distinct steps in the drill core logging process. A meaningful interpretation of the drill core logging data is often difficult due to inconsistencies in the logging process and shortcomings in the data management. Such errors and deficiencies can significantly influence the interpretation of the ground conditions. Common sources of error in the drill core logging process include careless drill core handling, inconsistencies in the logging criteria, and the lack of a well-structured data management system. These difficulties can be mitigated or even avoided by identifying the source of error, implementing measures to correct the inconsistencies and by establishing a clear documentation system for the drill core logging process. | diamond drilling, drill core logging, quality control, data management
T06: Geological investigation and characterizationYuanyuan WEI, Hui WUPeking University, People's Republic of ChinaInvestigation of the effect of matrix on tracer transport processes in subsurface fractured reservoirsTracer testing is a commonly used method to characterize flow and transport in subsurface fractured reservoirs. The interpretation of tracer recovery data generally requires numerous forward simulations of tracer transport in the underlying fracture and matrix. Previous studies have attempted to alleviate the associated computational burden by neglecting the matrix, but the impact of such a simplification remains unclear. This study systematically investigates the effects of matrix on tracer transport processes under various fracture/matrix parameters and tracer injection conditions through an analytical solution. Based on the results, we discuss the situations in which matrix has minimal effect on tracer transport and can be ignored during inversion/data assimilation. A dimensionless number that integrates fracture/matrix parameters and injection parameters is proposed to estimate matrix effect on tracer transport. The dimensionless number offers an easy yet practical way to quantify matrix effect, providing informative guidance for model development in tracer data interpretation. | Tracer transport, fractured reservoir, matrix effect, tracer injection condition, dimensionless number
T06: Geological investigation and characterizationThomas DICKMANN (1), Jozsef HECHT-MÉNDEZ (1), Dirk KRUEGER (1), Christoph SINKOVEC (2), Christian SCHÖNLECHNER (2)1: Amberg Technologies AG, Switzerland; 2: Jäger Bau GmbH, Bludenz, AustriaRapid seismic data acquisition in a TBM road tunnel excavation with segmental liningDedicated tunnel reflection seismic is a reliable geological exploration tool. In this method, 24 boreholes are prepared along a tunnel wall, which serve as seismic sources. In four additional boreholes, tri-axial seismic sensors are installed. By recording P- and S-waves propagating through the rock mass, seismic velocities are obtained, and an estimation of rock mechanical properties is possible. Changes in these properties allow for better understanding of the rock mass condition ahead of the face and timely identification of hazardous zones. Experiences on using reflection seismic during the construction of a double-shield TBM road tunnel in Switzerland are presented. Data acquisition was carried out by the tunnel contractor and data processing and evaluation by specialists in tunnel seismic. With 17 seismic measurements, a forecast of the rock mass was made over a length of 2,200 meters. Furthermore, the disturbance-free seismic data acquisition could be tested using an innovative next-generation hardware. | in-tunnel reflection seismic, geological forecast, rock mechanical parameters, site characterization
T06: Geological investigation and characterizationHong-Gyu LEEOriental Consultants Global, Tokyo, JapanPavement failure and flooding of tunnel in limestone geologyThis paper describes a case study of cause investigation and countermeasure on pavement failure and flooding in a under service tunnel during a heavy rain constructed by NATM in limestone geology. Since caverns of various sizes were confirmed and a large amount of groundwater flowed into the tunnel during the excavation, the cause is assumed to be the high water pressure acting on the caverns connected to the lower part of the pavement, which could not be visually confirmed when the tunnel was excavated. After confirming the soundness of the tunnel structures and pavement concrete by non-destructive testing methods, the cause investigation mainly focused on reconfirming the original excavation surface under the tunnel pavement. A countermeasure was adopted to allow free drainage through the confirmed small caverns and new drilling holes to prevent the reoccurrence of high water pressure in the small caverns around the tunnel. | Limestone, tunnel, cavern, water pressure, pavement failure, countermeasure
T06: Geological investigation and characterizationEmelie GAGNON, Jennifer J. DAYQueen's University, CanadaInterpreting variability of uniaxial compressive strength with insights from vein microstructuresThe uniaxial compressive strength (UCS) test is regularly used to derive rockmass strength and stiffness properties for geomechanics numerical modelling. While the test is straightforward, selecting representative material properties from a testing suite constrained by economics relies on the practitioner’s experience. This is challenging in veined rocks that exhibit significant variability in the results. To reduce this uncertainty, this study investigates the influence of intravein grain-scale geometric heterogeneity and orientation on the emergent veined specimen strength. Veins exhibit a spectrum of microstructures depending on the geological boundary conditions during their formation. Here, this is captured in a suite of 2D finite-element grain-based UCS experiments on specimens containing a single calcite vein. Results indicate that intravein grain orientation in veins with anisotropic grain arrangements is as influential on strength as the overall orientation of the vein (15-85% strength reduction) while isotropic crystal-bridged veins are less sensitive to orientation (20-45% strength reduction). | Geomechanical laboratory testing, uniaxial compressive strength (UCS), hydrothermal veins, grain-based modelling (GBM), vein microstructures
T06: Geological investigation and characterizationCamila Broetto MILLI (1), Alberto Ferreira AMARAL (3), Ana Paula DAHER (2), Marcos NASCIMENTO (3), Silas Santos SALGADO (3), Daniel Chaves dos SANTOS (3)1: Universidade Federal de Ouro Preto, Ouro Preto, Brazil; 2: Universidade Federal de Minas Gerais, Belo Horizonte, Brazil; 3: DF+ Engenharia, Belo Horizonte, BrazilDiagnosis of bench stability conditions in an iron ore open pit in the Quadrilátero Ferrífero/Minas Gerais/BrazilThe Quadrilátero Ferrífero, an important mineral province located in the state of Minas Gerais/Brazil, is influential for its world class deposits of commodities, such as iron ore. As in any other excavation, it is fundamental to grant the necessary bench slope stability conditions for the operation of its open pits. In this scenario, this paper develops products that supports the primary part of the diagnosis and planning of mining conditions in an iron mine. Field mapping and geological survey allowed gather structural data that supports geotechnical zoning of current slopes; kinematic analysis considering geometric conditions and the definition of potential types of failure mechanisms. This provided the overview of planar, wedge and flexural toppling occurrences in specific regions of the current operation. Corrective measures and geometric recommendations are discussed, as solution to ensure the stability of the structures and maintaining the production of this important commodity. | Slope Stability, Bench Analysis, Types of Failure, Quadrilátero Ferrífero
T06: Geological investigation and characterizationMartin ZIEGLER (1,4), Markus FURCHE (2), Thies BEILECKE (2), Thomas BURSCHIL (2), Anne OBERMANN (3), Qinghua LEI (4), Chenxi ZHAO (4), Simon LOEW (4)1: Swiss Federal Office of Topography (swisstopo); 2: German Federal Institute for Geosciences and Natural Resources (BGR); 3: Swiss Seismological Service (SED); 4: Department of Earth Sciences, ETH Zurich (ETHZ)Monitoring damage evolution in a tectonically faulted clay shale — an experiment of the Mont Terri URLThe Progressive Failure (PF) project explores experimentally and numerically structurally-controlled damage evolution in faulted Opalinus Clay shale at 1:5 scale in the Mont Terri URL, Switzerland. The in-situ experiment consists of a central, large-diameter experiment borehole (representing a repository drift) and six monitoring boreholes. The experiment borehole intersects tectonic fault planes and a major fault zone; its air humidity is controlled to simulate open and closed drift phases. The rock mass damage evolution is recorded by manifold techniques, including borehole photogrammetry, active seismic and electrical resistivity tomographies, and recordings of pico-seismicity, aiming at detecting and observing damage initiation and evolution around the borehole. A discontinuum numerical model is built to mimic the tectonic fractures explicitly and investigate the damage evolution around the experiment borehole. This paper provides an introduction to the experiment and highlights key datasets collected over the first two years of the project. | structurally-controlled failure, Opalinus Clay shale, in-situ experiment, electrical and seismic tomography, borehole photogrammetry, numerical discontinuum simulation
T06: Geological investigation and characterizationGabriela Buitrago FRAINZ, Gustavo Vinicius GOUVEIAVale, BrazilGeotechnical parameters prediction from geophysical logging data using supervised learning methodsRotary percussion drilling, despite being more agile and economical, does not provide the recovery of intact material as in traditional methods. With the use of this type of drilling, obtaining geotechnical parameters from alternative methodologies, such as geophysical logging, becomes of fundamental importance. Currently, however, geophysical logging does not meet the need to describe cores obtained by conventional drilling, due to methodologies established for geotechnics are based on tactile-visual parameters. Therefore, an opportunity is identified in the application of machine learning algorithms that use different data sources to obtain geotechnical parameters. Three algorithms were applied to the data sources and the scores varied depending on the comparisons and the acceptance criteria. It was observed that when the adjustment sequence is made in a more flexible criteria of acceptance, high levels of accuracy are achieved, which makes this tool practicable in geotechnical projects. | Machine Leaning, Geophysical, Geotechnical Logging, Mining, Supervised Learning
T06: Geological investigation and characterizationRamiro GARCÍA-LUNA, Salvador SENENT, Rafael JIMENEZE.T.S.I. de Caminos, Canales y Puertos, Universidad Politécnica de MadridApplications of the Structure from Motion photogrammetric technique to solve geotechnical problems at different scalesThe Structure from Motion (SfM) photogrammetric technique has been widely used, due to its ease of use and low cost, as an excellent alternative for remote 3D rock mass characterization. This technique uses only the information obtained from the digital images acquired with a regular camera to generate very high-resolution 3D models. However, this technique is widely influenced by environmental and physical conditions (degree of luminosity, distance to the target, geometry, etc.) of each case. In this work, we present our previous experiences, from a micro-scale application (in the laboratory) for small-scale roughness analysis, to a large-scale application (in the field) for the characterization of long slopes using drones. For each application, different methodologies have been proposed, adapting the SfM technique and developing innovative solutions. The obtained results confirm the applicability of SfM to efficiently solve rock engineering problems at different scales and under different conditions. | Structure from Motion, photogrammetry, rock roughness, rock characterization, UAVs
T06: Geological investigation and characterizationChao ZHANG, Wei WUNanyang Technological University, SingaporeSmart detection of limestone cavities in dense urban citiesUndetected cavities pose a great threat to underground construction in the limestone formations. In dense urban areas, additional challenges exist, such as fast and unnoisy field operations. Here we reported a new method to extract the characteristic energy of scattered and reflected signals for detection of limestone cavities. Comparing to the traditional seismic methods, this method does not require the seismic inversion and can thus achieve nearly real-time detection. The scattered and reflected signals are used to derive an anomaly score based on a signal processing framework, including multi-scale division and selection as well as enhanced low-rank feature extraction, to quantify possible locations of limestone cavities. We conducted a cavity detection test and demonstrated accurate detection of the horizontal location of a limestone cavity, but the accuracy of vertical location relies on the P-wave velocities of geologic layers. | Seismic imaging, limestone cavities, urban environment, field validation