bluuebunny/crossref_metadata_2025_split huggingface dataset:
Degradation of Fracture Characteristics on Coconino Sandstone Due to Water Content
Authors: Ko T Y 
Published: January 2023

AbstractThe water content of a rock affects its fracture characteristics, such as strength and fracture toughness. In this study, the effect of water content on the fracture characteristics, such as strength, fracture toughness and subcritical crack growth index under shear loading for Coconino sandstone was investigated. Here, experiments were conducted in two cases: completely dry and fully saturated. In particular, a short-beam compression specimen was employed to examine the fracture characteristics due to shear; in addition, the shear strength, mode II fracture toughness, and subcritical crack growth index under shear stress were obtained. Consequently, the shear strength and mode II fracture toughness decreased as the water content increased; however, the subcritical crack growth index remained almost the same without significant alterations. The effect of water on the strength reduction of rocks is related to chemical and physical corrosion, pore pressure increase, and frictional reduction. Previous investigations on the deterioration of strength by water have yielded similar results in this research. Under saturated conditions, the shear strength decreased by 15.5%, and the fracture toughness decreased by 11.8%, compared with dry conditions. Regardless of the dry or saturated condition, the subcritical crack growth indexnexhibited similar values.
Development and verification of a long-distance survey ahead of the tunnel face using excavation blasting as seismic source
Authors: Yamagami M , Ichiki T , Ito S , Murata K 
Published: January 2023

Abstract
In mountain tunnelling, it is important from the point of construction safety and effectiveness to obtain information about the ground ahead of excavation, such as the positions of fracture zones and possible water inflows which may pose problems during construction. Seismic reflection surveys are used to survey the ground ahead of the face. While the maximum surveyable distance of conventional methods is 100-150 m, the authors are working on extending this ability to provide a long-distance outlook for tunnelling work and have developed a method known as Blast Excavation Prospecting (T-BEP). As a result of comparing conventional method in a verification experiment, it is found that T-BEP can detect a fracture zone with a width of 35 m about 350 m ahead of the face with an error of about 40 m..
Effect of anisotropy of fracture surface on fluid flow
Authors: Torkan Masoud , Khorasgani Amir Hosseini , Uotinen Lauri , Bagbanan Alireza , Rinne Mikael 
Published: January 2023

Abstract
Characterization of fluid flow through rough fractures is an important issue in designing underground excavations, such as nuclear repositories or geothermal applications. Fluid flow could be influenced by several parameters such as contact areas, aperture, hydraulic and mechanical conditions. Contact area and aperture could be two crucial geometrical factors which control hydraulic and mechanical behaviors of fractures. These factors are rarely isotropic, and anisotropy is observed in different directions. In this research, photogrammetry, as a high precision method, was used to analyze morphology of a tensile fracture induced in granite. Experimental and numerical stress-flow tests on rock fracture were conducted in two different directions with diverse normal stresses and water pressures. Analyzing the regenerated 3D model of the fracture and hydromechanical tests predicts the anisotropy in flow rates in different directions. Numerical and experimental results are well fitted particularly in low-stress conditions. The obtained results show that anisotropy affects permeability since outlet flow rates in the different directions with the same initial water pressures differ by 7 % in experiments and 4% in numerical modeling.
Geomechanical characterization and analysis of the influence of durability tests on metabasalts
Authors: dos Santos Lemos Carolina Crissafe , de Souza Pires Costa Carolina , de Faria Silva Natália , Marques Eduardo Antonio Gomes , Jaques Daniel Silva 
Published: January 2023

Abstract
Laboratory tests are essential to provide knowledge on rock matrix properties, to predict field behaviour and to plan and execute improved engineering design. The paper presents the results of several laboratory tests performed on samples of a basic rock from N4 mine, located at Carajás Complex, on sound and cycled (artificially weathered) rock material. Carajás complex is located in Carajás sierra, Amazon region, North of Brazil, and is currently known as the biggest mineral province of the world. This region has great geological and economical importance and, on this context, studies related to rock mechanics are essential to evaluate open pit stability on long term periods. This study comprises a mineralogical, physical and geomechanical characterization of a metamorphised basalt rock, throughout a comprehensive laboratory test campaign encompassing the following tests: thin section description (including micropetrographic and weathering indices determination), physical properties, uniaxial compressive strength, point load strength, P wave propagation velocity, Schmidt hammer and durability test (accelerated cycling). Results from other works in the literature are presented to provide a basis for comparison. Petrographic analyses allowed classifying the rock as a hydrothermalized metabasalts. Micropetrographic index has shown that rock presents low weathering, with a higher quantity of sound minerals. Porosity, dry and saturated specific weight and water absorption capacity were calculated for samples with and without cycling and the results show that the number of water – salt cycles were not sufficient to cause a significant change on these physical indices. Wave propagation velocities were determined and the results are similar to the ones found in literature for similar rocks. Schmidt hammer were used to determine uniaxial compressive strength (UCS) trough Miller abacus. Another strength tests performed on rock samples were point load test, and the results were also used to correlate with UCS and other studies results. All these results were later compared with uniaxial compressive strength tests data and the values were similar. Furthermore, data from UCS tests were also used to calculate elasticity (Young) modulus and the material has shown a highly elastic behaviour.
Characterisation of Fine Particles Generated at Draw points During Sub-Level Cave Mining for Assessment of Mud Inrush Hazard
Authors: Musolino Matthew , Karakus Murat , Cox David , Chester Chris , Balog Glen , Nguyen Giang 
Published: January 2023

Abstract
The inundation of mud, known in the industry as ‘mud inrush’ is a hazard associated with caving mining methods. Ineffective inrush management strategies can result in sections of the mine lost, or in some cases, fatalities. Previous studies have focused on water and various percentages of fines (particles <2mm - <5cm) in draw points as risk indicators for the hazard. Standardised material tests were conducted on samples collected from a sub-level caving operation in Australia. Concrete slump tests were carried out on two in-situ mud samples based on their observed mobility. The immobile sample had 6% more material below 300μm and required a 2% higher moisture content to begin slumping and turn from plastic to soft flow. Shear strength tests reflected the higher plasticity of the immobile sample with a cohesive strength of 23.08 kPa compared to the second mobile sample of 9.16 kPa. The elemental assay revealed the mobile sample had lower iron oxide, and higher silicon oxide content than the immobile sample. The work presented in this paper indicates that fine fractions <0.6mm noticeably affect laboratory test results that are hypothesised to relate mud flowability and potential hazard.
Geometrical aspects in the consideration of actual opposed surface along shearing direction in rock joints
Authors: Guerrero-Miguel Diego-José , Prendes-Gero María-Belén , Álvarez-Fernández Martina-Inmaculada , González-Nicieza Celestino , Conde-Fenández Lucía 
Published: January 2023

Abstract
Shear behaviour of rock joints is strongly influenced by the roughness of its surface as the different failure mechanisms will be conditioned by the shape and distribution of the asperities and undulations in it. Currently, this surface can be digitalized using scanning methods directly in the field or in representative laboratory samples. After that, the surface is digitally reproduced using triangulation methods. This allows to analyse it using stablished parameters that do not depend on the arbitrariness of the technician. Despite the fact that 2D roughness parameters are still of great importance, these techniques are nowadays provoking a tendency to implement 3D measuring methods that allow to treat all the surface simultaneously and thus gathering valuable information of the rock joint as a whole. The vast majority of the 3D most powerful methods consider the area of the surface that is opposed against the shearing direction in order to determine the roughness, anisotropy and peak shear strength of the rock joint. However, not always the whole surface of each triangle that faces against shearing direction should be considered. In this work, a new methodology to consider the actual area of each triangular element that is involved in the shearing process is mathematically derived. Therefore, improving the accuracy of current methods, as well as the truthfulness of the mechanical characterization of rock joints.
A new approach to reduce blasting-induced vibration in tunnel blasting by utilizing the initiation time scatter of detonator
Authors: Yoon Y , Baek J , Jeong M S , Jeon S 
Published: January 2023

Abstract
The charge weight per delay is one of the major variables in empirical models for predicting the peak particle velocity in tunnel blasting. In many instances, the corresponding initiation times of the detonators often overlaps. The overlaps occur because of the initiation time scatter of each of the detonators. The overlap, in turn, causes an increased charge weight per delay, which consequently causes an increase in the blast-induced vibration. In this study, a novel technique is introduced for development of a blasting pattern exploiting the initiation time scatter of the detonators. The initiation time of 423 detonators was measured using a vibration monitoring instrument and a high-speed camera. From the data obtained, a standard deviation of the initiation times of the detonators was determined. The probability of overlap of the initiation times of the detonators was calculated using a Monte Carlo simulation. After simulating both a new blasting pattern utilizing the initiation time scatter of the detonator and the conventional blasting pattern 10,000 times each, it was determined that, in the new blasting pattern, the number of sets in which four or more blastholes initiated simultaneously decreased from 17,595 to 1604. Moreover, the probability that four or more blastholes initiated simultaneously in a blasting round decreased from approximately 70% to 12%.
An investigation on relations between dissipated energy and dynamic compressive strength of Kemi-peridotite at high strain rates
Authors: Ozoji T M , Zhang Z X , Aladejare A E , Zhang N , Guan X 
Published: January 2023

Abstract
Dynamic properties of rocks are essential for planning sustainable engineering structures in regions prone to dynamic loading as well as effective fragment size distributions during quarrying activities. Due to the vast application of dynamic rock properties, several studies have been conducted on the context. However, studies on relations between dissipated energy and dynamic compressive strength are scanty. The aim of the study is to investigate relations between dynamic compressive strength and dissipated energy during fragmentation of Kemi-peridotites at high strain rates. To achieve this, cored specimen was prepared according to recommendations of the International Society for Rock Mechanics and fractured using the split Hopkinson’s pressure bar. Results indicate that the dissipated energy during rock fracture generally increases at high dynamic compressive stress. However, the regression square of dissipated energy and dynamic compressive strength plots suggest poor relations between both variables. Further evaluation of measured strain at maximum dynamic compressive stress indicates that strain in specimen continued significantly after maximum dynamic compressive stress was attained. However, evaluations on relations between dissipated energy and strain indicates that energy dissipation continued along a significant portion of the measured strain during rock fracture at high strain rates. Visual evaluation of broken fragments also indicates good relations between dissipated energy and fragmentation results of Kemi-peridotites at high strain rates. Based on study findings, dissipated energy provides improved indices for evaluating strain and fragment size distribution while dynamic compressive stress provides indices on maximum stress required for rock failure.
Virtual reality learning system for remote rock mass mapping
Authors: Janiszewski Mateusz , Zhang Xiaoyun , Uotinen Lauri , Rinne Mikael 
Published: January 2023

Abstract
Rock mass quality mapping is essential in rock engineering and mining projects. However, the current manual mapping approach and its teaching are restricted due to the dangerous nature of work near rock walls and the constraints of resources. Therefore, a virtual reality learning system for teaching remote mapping of rock mass quality was developed at Aalto University. Two rock wall sections of an underground tunnel and a roadside rock-cut were scanned using photogrammetry and imported as high-resolution textured 3D models. The user wears a head-mounted display and performs mapping using a pointing device. The system collects the measurements automatically and assists the user in rock mass mapping. Along with the development of the system, qualitative research was conducted to evaluate user performance in a gamified learning system. The results demonstrate that with proper game elements implemented, the learning system can be used to steer student behaviour towards the target range. Once set up, the VR system is a tireless, user-paced aid in training and teaching.
Assessing the tunnel stability in brittle rocks based on strain bursting assessment
Authors: Aujmaya Lans , Vazaios Ioannis , Paraskevopoulou Chrysothemis 
Published: January 2023

AbstractStrain bursting is a phenomenon associated with deep underground excavations and tunnelling in brittle hard rocks that result in a sudden and violent failure, posing high risks and damage. This work aims to assess the strain bursting and the energy response characteristics and develop a guideline that can be utilized in the preliminary investigation stage. The obtained results are intended to enable predicting different brittle behaviours in deep geological environments. Elastic stress analysis using the DISL approach based on boundary element method is established (EX3-software) for the assessment of two tunnel geometries (circular, horseshoe) in granitic rock mass. Two different stress states are modelled to simulate the potential stress regime. The analysis’ results demonstrate that different geometries affect the energy storage capacity and result in different behaviour regarding the bursting potential of the rock mass.
Use of flow-back and pressure rebound data improves the minimum stress estimation in a tight claystone formation
Authors: de Lesquen C , Armand G 
Published: January 2023

Abstract
Andra is in charge of the long-term management of all radioactive waste in France. It has acquired between 2000 and 2008 a vast amount of stress data around the area selected to host the French deep geological repository for high activity and long-lived radioactive waste. The minimum principal stress was estimated from hydraulic fracturing tests and the fracture closure pressure was interpreted during the shut-in phase. However, in the Callovo-Oxfordian claystone, this method results in a minimum horizontal stress that is much larger than the vertical stress even when vertical fractures were clearly generated. As the uncertainty on the weight of the overlying sediments is low, the validity of this technique in a tight claystone formation with very limited leak-off is questioned. Several tests were reinterpreted using the flow-back data and the pressure rebounds when they were recorded. The new interpretation gives consistent results between the wells drilled around the Meuse/Haute-Marne underground research laboratory and the magnitude of the minimum principal stress matches well the actual orientation of the induced fractures. These data support the use of flowback tests as the preferred stress determination technique in tight formations.
Predicting rockburst damage scale in seismically active mines using a classifier ensemble approach
Authors: Toksanbayev N , Adoko A C 
Published: January 2023

Abstract
Rockburst still remains one of the most important sources of hazards in underground mine industry. This phenomenon results in many accidents and casualties in many underground mine projects around the world. Despite the scientific achievements in rock mechanics and engineering, the accurate prediction of rockburst damage potential is still challenging due to the complexity of seismic event occurrence. Hence, this paper aims to develop a reliable classifier ensemble to rockburst intensity in underground mine excavations subjected to seismicity. High quality rockburst database consisting of 254 case histories was used for the study. The classifier ensemble was developed through aggregation of several commonly used machine learning classifiers using the weighted voting. The performance of the classifier ensemble was evaluated using several indicators, namely: accuracy, recall, precision, and F1-score. The overall results indicate that the proposed classifier ensemble achieved good performance metrics and outperformed some existing empirical methods. It is concluded that the classifier ensemble could assist engineers to properly assess rockburst damage and contribute to selecting adequate ground control measures.
Effects of the initial stress and spalling strength on spalling around deposition holes and tunnels
Authors: Figueiredo B , Vatcher J , Sjöberg J , Ivars D Mas 
Published: January 2023

Abstract
Spalling in the deposition holes and tunnel stability are of concern for the design of deep geological repositories for spent nuclear fuel. A 3D numerical stress model, including a single deposition tunnel and multiple deposition holes to analyse the potential for spalling resulting from the excavation phase, was developed for the proposed repository location at the Forsmark site. Several potential initial stress field cases and spalling strengths of the intact rock were considered. The magnitudes of the factor of safety, the spalling depth, the minor principal stress, and the differential stress were evaluated. The results showed that no spalling in the central deposition hole is indicated for the most likely stress field, and the occurrence of spalling and the spalling depth are minimised for a maximum horizontal stress aligned approximately parallel to the tunnel axis. For spalling occurrence and depth of spalling, the magnitude of the maximum horizontal stress is more critical than its orientation, and the spalling strength is more critical than the magnitude of the maximum horizontal stress. No instability problems were indicated in the vicinity of the roof for all analysed stress cases.
An advanced constitutive model for transversely isotropic rock - Evaluation of two different regularization approaches
Authors: Mader Thomas , Schreter Magdalena , Hofstetter Günter 
Published: January 2023

Abstract
The mathematical description of the material behavior of rock is a demanding task in engineering practice. Rock is classified as a frictional cohesive material characterized by highly nonlinear mechanical behavior with irreversible deformation, strain hardening, strain softening and degradation of stiffness. In addition, depending on the origin of a particular rock type, the orientation of minerals and grains as well as the formation of stratification planes lead to inherent anisotropic behavior. Especially in stratified rock types like shales or phyllites, often the special case of transversely isotropic material behavior is encountered. In a previous work, a novel continuum-based material model for describing both, the highly nonlinear and transversely isotropic material behavior of rock, denoted as TI-RDP model, was presented. By means of the linear mapping of the Cauchy stress tensor into a fictitious isotropic configuration, an established isotropic damage plasticity model for rock was extended. In this contribution two different regularization approaches, which are well established for isotropic models, i.e., the mesh-adjusted softening modulus and the implicit gradient-enhancement, are adopted for the TI-RDP model. Based on uniaxial tension and triaxial compression tests considering different orientations of the principal material directions with respect to the direction of axial loading, their capabilities are assessed in terms of predicting the direction-dependent mechanical behavior in a mesh-insensitive manner.
Weakening of tensile strength of granitic rock by HV-HF-AC actuation of piezoelectric properties of Quartz: a 3D numerical study
Authors: Saksala T , Ruiz R A Rubio , Kane A , Hokka M 
Published: January 2023

Abstract
High-voltage and high-frequency alternating current (HV-HF-AC) excitation of piezoelectric properties of Quartz is a potential method to induce cracks in granite. This was recently shown in a numerical feasibility study [6], where cracking was induced on cylindrical rock samples made of granite by sinusoidal AC excitation at the frequency of ~100 kHz and the amplitude of ~10 kV. However, this study did not investigate the weakening effect due to this cracking on the tensile strength of the sample. The present study addresses this topic numerically. For this end, a numerical method based on 3D embedded discontinuity finite elements for rock fracture and an explicit time stepping scheme to solve the coupled piezoelectro-mechanical problem is adopted. Rock heterogeneity and anisotropy are accounted for at the mineral mesotructure level. A preliminary numerical simulation demonstrates that the HV-HF-AC treatment reduces the tensile strength of a cylindrical granite sample by 12 %, making it thus a potential non-conventional pre-treatment method in comminution and excavation of Quartz bearing rocks and ores.