Subjects -> MINES AND MINING INDUSTRY (Total: 82 journals)
 Showing 1 - 42 of 42 Journals sorted alphabetically Applied Earth Science : Transactions of the Institutions of Mining and Metallurgy       (Followers: 4) Archives of Mining Sciences       (Followers: 1) BHM Berg- und Hüttenmännische Monatshefte       (Followers: 1) Canadian Mineralogist       (Followers: 5) CIM Journal Clay Minerals       (Followers: 8) Contributions to Mineralogy and Petrology       (Followers: 11) Environmental Geochemistry and Health       (Followers: 2) European Journal of Mineralogy       (Followers: 12) Extractive Industries and Society       (Followers: 2) Gems & Gemology       (Followers: 1) Geology of Ore Deposits       (Followers: 3) Geomaterials       (Followers: 2) Geotechnical and Geological Engineering       (Followers: 8) Ghana Mining Journal       (Followers: 3) Gold Bulletin International Journal of Coal Geology       (Followers: 2) International Journal of Coal Preparation and Utilization       (Followers: 1) International Journal of Coal Science & Technology       (Followers: 1) International Journal of Hospitality & Tourism Administration       (Followers: 14) International Journal of Minerals, Metallurgy, and Materials       (Followers: 8) International Journal of Mining and Geo-Engineering International Journal of Mining and Mineral Engineering       (Followers: 5) International Journal of Mining Engineering and Mineral Processing       (Followers: 5) International Journal of Mining Science and Technology       (Followers: 4) International Journal of Mining, Reclamation and Environment       (Followers: 4) International Journal of Rock Mechanics and Mining Sciences       (Followers: 6) Journal of Analytical and Numerical Methods in Mining Engineering Journal of Applied Geophysics       (Followers: 15) Journal of Central South University       (Followers: 1) Journal of China Coal Society Journal of Convention & Event Tourism       (Followers: 4) Journal of Geology and Mining Research       (Followers: 11) Journal of Human Resources in Hospitality & Tourism       (Followers: 8) Journal of Materials Research and Technology       (Followers: 2) Journal of Metamorphic Geology       (Followers: 15) Journal of Mining Institute Journal of Mining Science       (Followers: 2) Journal of Quality Assurance in Hospitality & Tourism       (Followers: 5) Journal of Sustainable Mining       (Followers: 2) Journal of the Southern African Institute of Mining and Metallurgy       (Followers: 5) Lithology and Mineral Resources       (Followers: 3) Lithos       (Followers: 9) Mine Water and the Environment       (Followers: 4) Mineral Economics Mineral Processing and Extractive Metallurgy : Transactions of the Institutions of Mining and Metallurgy       (Followers: 11) Mineral Processing and Extractive Metallurgy Review       (Followers: 4) Mineralium Deposita       (Followers: 4) Mineralogia       (Followers: 2) Mineralogical Magazine       (Followers: 1) Mineralogy and Petrology       (Followers: 2) Minerals Minerals & Energy - Raw Materials Report Minerals Engineering       (Followers: 9) Mining Engineering       (Followers: 5) Mining Journal       (Followers: 3) Mining Report       (Followers: 2) Mining Technology : Transactions of the Institutions of Mining and Metallurgy       (Followers: 2) Mining, Metallurgy & Exploration Natural Resources & Engineering Natural Resources Research       (Followers: 8) Neues Jahrbuch für Mineralogie - Abhandlungen       (Followers: 1) Physics and Chemistry of Minerals       (Followers: 4) Podzemni Radovi Rangeland Journal       (Followers: 1) Réalités industrielles Resources Policy       (Followers: 4) Reviews in Mineralogy and Geochemistry       (Followers: 4) Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica Rock Mechanics and Rock Engineering       (Followers: 6) Rocks & Minerals       (Followers: 2) Rudarsko-geološko-naftni Zbornik Stainless Steel World       (Followers: 17) Transactions of Nonferrous Metals Society of China       (Followers: 9)
Similar Journals
 Rock Mechanics and Rock EngineeringJournal Prestige (SJR): 2.328 Citation Impact (citeScore): 3Number of Followers: 6      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1434-453X - ISSN (Online) 0723-2632 Published by Springer-Verlag  [2469 journals]
• Evaluating the Response of a Tunnel Subjected to Strike-Slip Fault Rupture
in Conjunction with Model Test and Hybrid Discrete–Continuous Numerical
Modeling

Abstract: Abstract The current paper evaluates the response of a tunnel subjected to strike-slip fault rupture with experimental and numerical approaches. Some state-of-art techniques were adopted in the analysis. A new formula containing sodium silicate was used for the similar material. Endoscope technique was used in the model test to log the crack propagating inside the tunnel. And hybrid discrete–continuous modeling was introduced to perform a sophisticated numerical investigation. Two small-scale model tests were carried out, in which the interaction of the tunnel with the fault rupture, the deformation pattern, and the strain evolution and crack propagation in the tunnel liner were observed. The model tests indicate that the failure of the tunnel mainly resulted by the faulting-induced circular cracks concentrated in the vicinity of the shear zone and longitudinal cracks at the passive side portion. Then, the hybrid DEM-FDM model was constructed and calibrated based on the experimental data, with which the response and mechanism of the tunnel subjected to strike-slip fault rupture were numerically investigated to identify the influences of some important factors. The longitudinal and transverse deformation profiles of the tunnel were found to be dominated by the rock mass condition and the buried depth of the tunnel. And the tunnel’s design factors have significant effects on the stress and failure mode of the liner. For a soft or thin tunnel liner, the failure zones were more concentrated. The tunnel would fail in a ‘shear’ mode. In contrast, for a hard or thick liner, the magnitude of the tensile strain is less, yet the tension failure area is larger. The tunnel would fail in a ‘squeeze’ mode. Based on the obtained results, suggestions on the design of tunnel liner against the strike-slip fault rupture were proposed.
PubDate: 2022-05-22

• 4D Synchrotron X-ray Imaging of Grain Scale Deformation Mechanisms in a
Seismogenic Gas Reservoir Sandstone During Axial Compaction

Abstract: Abstract Understanding the grain-scale processes leading to reservoir compaction during hydrocarbons production is crucial for enabling physics-based predictions of induced surface subsidence and seismicity hazards. However, typical laboratory experiments only allow for pre- and post-experimental microstructural investigation of deformation mechanisms. Using high-resolution time-lapse X-ray micro-tomography imaging (4D µCT) during triaxial deformation, the controlling grain-scale processes can be visualized through time and space at realistic subsurface conditions. We deformed a sample of Slochteren sandstone, the reservoir rock from the seismogenic Groningen gas field in the Netherlands. The sample was deformed beyond its yield point (axial strain > 15%) in triaxial compression at reservoir P–T-stress conditions (100 °C, 10 MPa pore pressure, 40 MPa effective confining pressure). A total of 50 three-dimensional µCT scans were obtained during deformation, at a spatial resolution of 6.5 µm. Time lapse imaging plus digital volume correlation (DVC) enabled identification of the grain-scale deformation mechanisms operating throughout the experiment, for the first time, both at small, reservoir-relevant strains (< 1%), and in the approach to brittle failure at strains > 10%. During small-strain deformation, the sample showed compaction through grain rearrangement accommodated by inter-granular slip and normal displacements across grain boundaries, in particular, by closure of open grain boundaries or compaction of inter-granular clay films. At intermediate and large strains (> 4%), grain fracturing and pore collapse were observed, leading to sample-scale brittle failure. These observations provide key input for developing microphysical models describing compaction of the Groningen and other producing (gas) reservoirs.
PubDate: 2022-05-21

• Stability Analysis of Surrounding Rock in Underground Chamber Excavation
of Coral Reef Limestone

Abstract: Abstract The exploitation and utilization of underground space in the coral reef limestone has become more and more important for the development and construction of ocean engineering in the world. Due to the particular composition and development environment of the reef limestone, its surrounding rock stability in underground engineering construction is significantly different from that of other terrestrial rocks. This paper focuses on the stability of surrounding rock in underground chamber excavation of coral reef limestone by physical model experiments and numerical calculation. First, the quartz sand, barite powder, high-strength gypsum, calcareous sand, cement and water are selected as the raw materials to configure the similar materials of reef limestone based on the similarity theory. Second, according to the difference of the lining and span of the chamber, three geological models are designed and the underground chamber excavation experiments of reef limestone are carried out. The change laws of displacement and stress during the excavation are analyzed, and the influence of lining support and chamber span on the stability of the surrounding rock is obtained. Finally, the numerical simulation is used to simulate the excavation of the foundation model, and the physical model experiment is verified by comparing with the numerical calculation results. The results show that: when reducing the lining support or increasing chamber span, the displacement and stress release rate of surrounding rock both increase during the excavation of chamber. The average error of displacement and stress release rate between the physical model experiment results and the numerical simulation results is about 10%, which verifies the accuracy of the physical model experiment results.
PubDate: 2022-05-21

• Application of Full-Scale Experimental Cutterhead System to Study
Penetration Performance of Tunnel Boring Machines (TBMs)

Abstract: Abstract Rock penetration is the most important function of tunnel boring machines (TBMs). Based on a detailed review of TBM rock penetration research, this study introduces a rarely reported full-scale experimental cutterhead system that combines the advantages of in situ penetration tests and laboratory rock-breaking tests. The main focus of this study is to investigate TBM penetration performance using this experimental cutterhead system. Nine groups of penetration tests were conducted on an integral concrete specimen with cutterhead rotational speed and net penetration varying from 1.9 to 5.9 r/min and 2.5 to 8.8 mm/r, respectively. The cutting force and chipping performance of each cutter were monitored, examined, and analyzed considering boreability and mechanical efficiency. The results indicate that the cutter normal force is unaffected by the cutter installment radius and cutterhead rotational speed. However, the muck weight and specific excavation rate increase in perfectly fitted exponential functions with increasing cutter position number, indicating that the cutting efficiency increases with cutter position number. Muck sieving results show that face cutters produce larger and more elongated chips than center cutters, as the extent of cutter side sliding declines with increasing cutter installation radius. The boreability index decreases in a perfectly fitted power function with increasing net penetration, indicating that the critical threshold for cutterhead net penetration is approximately 5 mms/rev. The proposed models predicting the cutter normal force and boreability index were compared with 13 sets of in situ penetration test data. This study can guide TBM excavations encountering rocks with equivalent strength and intactness.
PubDate: 2022-05-20

• Acoustic Emission Response Mechanism of Hydraulic Fracturing in Different
Coal and Rock: A Laboratory Study

Abstract: Abstract To examine the influence of lithology on the microseismic response mechanism during the process of coal and rock hydraulic fracturing (HF), we selected four lithological samples of coal, sandstone, shale, and mudstone, which are commonly found in coal-measure strata. The acoustic emission (AE) cumulative counts, AE energy, crack classification, AE peak frequency, and AE position of the four samples under natural conditions were studied, and the laws of crack propagation and evolution in the process of coal and rock HF were explained. We discovered the phenomenon of “bimodal frequency bands” during the HF of coal and rock samples. The results showed that the pressure curves and AE cumulative counts of the coal samples exhibited the largest fluctuations. The power-law distribution of AE energy has a discrete effect in the high-energy region and a plateau effect in the low-energy region. The AE energy power-law indexes of the mudstone samples are the largest, with the values of 0.64 and 0.61, whereas those of the shale samples are the smallest, with the values of 0.44 and 0.45. The crack classification of the samples of coal is mainly shear cracks, and the crack classification of the samples of sandstone, shale and mudstone is mainly tensile cracks. It is proposed to regard frequency band II as the dominant frequency band for HF in the coal, sandstone, and mudstone samples and frequency band I as the dominant frequency band for HF in shale samples.
PubDate: 2022-05-19

• In-situ Shear Modulus Determination by Pressuremeter Tests in Opalinus
Clay and Reconciliation with Laboratory Tests

Abstract: Opalinus Clay is the designated host rock for a deep geological repository of radioactive waste in Switzerland. The determination of its geo-mechanical properties relies heavily on laboratory tests on small specimens. To assess the in-situ elastic stiffness at a larger scale, pressuremeter tests were performed in Opalinus Clay at the Mont Terri Rock Laboratory, with the testing probe oriented both perpendicular and parallel to the bedding planes. The shear modulus of the Opalinus Clay is determined using the unload data of the pressuremeter tests in different lithofacies and at multiple expansion pressure levels. The measured shear modulus is dependent on the expansion pressure at the initial stage of the test but approaches a relatively constant value when a pressure magnitude of about 5 MPa is reached. The stiffness anisotropy of the Opalinus Clay, the rock mass disturbance, and the local fractures at test intervals can affect the measured moduli. In this test program, the impact of lithofacies was not evident at low expansion pressures and could not be evaluated at a greater expansion pressure. The shear modulus of the Opalinus Clay exhibits a nonlinear dependence on strain increment, which can be interpreted using a power-law stress–strain relationship. The small-strain nonlinearity is also dependent on the expansion pressures for the Opalinus Clay. At expansion pressures greater than 5 MPa, the strain-dependent shear moduli obtained from pressuremeter tests are comparable with those determined by triaxial tests on intact core specimens. At the shear strain increment of 0.1%, a secant shear modulus (parallel to bedding) of approximately 3 GPa for the intact Opalinus Clay can be concluded from both the pressuremeter and triaxial tests. Highlights High-quality pressuremeter tests are performed in Opalinus Clay to assess its in-situ static elastic stiffness using the unloading steps at multiple expansion pressure levels. Assuming axisymmetric borehole deformation, the shear modulus determined in the borehole oriented parallel to bedding is significantly lower than that determined in the borehole oriented perpendicular to bedding. The measured shear modulus can also be affected by the rock mass disturbance and the local fractures at the test interval. The interpreted secant shear modulus is nonlinearly dependent on the small strain increment during unloading, which can be characterized by a power-law stress-strain relationship. An agreement on the measured shear moduli (parallel to bedding) can be established between the pressuremeter and laboratory triaxial tests on intact Opalinus Clay when the strain dependency of the modulus is considered for both tests. This study presents a framework for bridging the elastic stiffness measurements of weak argillaceous rocks using high-quality laboratory and in-situ tests.
PubDate: 2022-05-16

• Assessment of Engineering Properties of Limy Rocks Using Friction-Transfer
Test: A Case Study

Abstract: Abstract Some expensive and challenging laboratory or field tests must be done to obtain the engineering properties of rocks. For avoiding time and cost consumption, some researchers have used simple tests to estimate some engineering properties. The friction-transfer test is partially destructive and can estimate the rock uniaxial compressive strength (UCS) using experimental equations or a previously prepared calibration graph. In this study, some engineering properties of seven types of limy rocks from Qom formation, collected from Hamadan province, were estimated using friction-transfer test results. Regression analysis between friction-transfer and physical properties tests show that the best relationship is between porosity (n%) and friction-transfer value (T) and torsion angle (θ) (R2 = 0.74). Friction-transfer engineering property regression analysis shows that the best relation is obtained between Brazilian tensile strength (BTS) and T, θ, because of the higher R2 (0.80). Relatively high coefficients of the determination indicate that the friction transfer can successfully predict the UCS of rocks. A conversion factor equal to 0.48 was obtained for estimating UCS by T values for this study data.
PubDate: 2022-05-16

• Rock Properties and Modelled Stress State Uncertainties: A Study of
Variability and Dependence

Abstract: Abstract The safety and sustainability of subsurface applications requires a profound knowledge of the local stress state which is frequently assessed using 3D geomechanical-numerical models. Various factors lead to generally large uncertainties in these models. The variabilities in the rock properties as one of the sources of uncertainties and their influence on the modelled stress state is addressed herein. A generic 3D geomechanical-numerical model is used to investigate the influence of different distributions of variability and their effect on different stress states. The variability in rock properties clearly affects the uncertainties in the stress state in a positive correlation with differences that depend on the affected component of the stress tensor. The basic observation is that largest uncertainties are observed in the normal components of the stress tensor where the variabilities apparently are most effective. The same rock property variabilities affect the shear components uncertainties to a significantly lesser extent. Variabilities in the Young’s modulus and the Poisson’s ratio chiefly affect the uncertainties in $$\sigma _{xx}$$ and $$\sigma _{yy}$$ . The density variability, however, leads to highest uncertainties in $$\sigma _{zz}$$ . In general, variabilities in the Young’s modulus are most effective, followed by the Density and then the Poisson’s ratio. Furthermore, an influence of the tectonic stress regime on how the variability in the rock properties affects the stress state is observed. At the same time only a small effect is observed for different stress magnitudes. The eventual uncertainties in a modelled stress state depend not only on the uncertainties in the rock properties but also whether the uncertainties are found mainly in the Young’s modulus, the Poisson’s ratio or the Density. These findings indicate the importance to regard variabilities in rock properties as a source for significant uncertainties in geomechanical-numerical models. It is proposed to use the derived relations for an inexpensive quantification of uncertainties by means of a post-computation assignment of uncertainties to a stress model.
PubDate: 2022-05-12

• Rock Strata Failure Behavior of Deep Ordovician Limestone Aquifer and
Multi-level Control Technology of Water Inrush Based on Microseismic
Monitoring and Numerical Methods

Abstract: Abstract The mining depth of most coal mines in North China has exceeded 1 km. The high seepage water pressure caused by high ground stress leads to the increasingly serious threat of water disaster in the mine. To explore the relationship and mechanism between water inrush from deep mining floor and grouting prevention, single-level grouting and multi-level cooperative grouting methods were carried out in Ordovician limestone confined aquifer of coal seam floor in Xingdong coal mine. Meanwhile, the temporal and spatial characteristics of rock fracture in the floor of deep mining face are revealed through the law of rock fracture microseismic. It is noteworthy that the occurrence time of water inrush and microseismic events have lag characteristics, that is, the occurrence time of microseismic events is earlier than that of water inrush. The multi-level cooperative grouting method can effectively control the non-uniform dissolution Ordovician limestone aquifer in-plane and vertical plane. Furthermore, single-level grouting and multi-level cooperative grouting methods are assumed to be unstable grouting and stable grouting. Besides, the flow pattern transformation characteristics of Ordovician limestone water in unstable to stable grouting are simulated by the finite element method. The results show that the energy inoculation level of fracture expansion around the aquifer decreases after stable grouting reinforcement. In other words, the multi-level cooperative grouting method can effectively strengthen and fill the water inrush channel and reduce the damage of high osmotic pressure to the aquiclude. It is of great significance to reduce the probability of water inrush in deep coal seam and ensure the mining safety of deep coal seam.
PubDate: 2022-05-12

• Heating-Dominated Fracturing of Granite by Open-Ended Microwave: Insights
from Acoustic Emission Measurement

Abstract: Abstract Microwave fracturing of hard rocks holds great promise in the civil, mining and tunnelling industries. The role of heating and cooling in the fracturing of rocks and when and where cracks initiate from and propagate to remain unclear and need to be addressed for future field applications of the technology. This study treated an alkali feldspar granite using a 6 kW industrial microwave source and a customised open-ended dielectric-loaded converging waveguide antenna. The real-time acoustic emission (AE) characteristics in the microwave heating and natural cooling phases were recorded and investigated. The surface temperature and P-wave velocity reduction of the specimens were also measured to quantify the thermal damage. The fracturing of granite is found to be tensile failure and is heating-dominated. Although a considerable amount of AE hits and events was detected in the cooling phase, they were of low energy, and therefore, the role of cooling in rock fracturing by open-ended microwave can be neglected. Fractures initiated from the exterior of the antenna and propagated towards the edges and the interior of the specimens. The cracks obtained from the AE localisation were in good agreement with those observed. With the increase of power level, the time for crack initiation was shortened, confirming the high-power effect.
PubDate: 2022-05-12

• A Numerical Characterisation of Unconfined Strength of Weakly Consolidated
Granular Packs and Its Effect on Fluid-Driven Fracture Behaviour

Abstract: Abstract Soft or weakly consolidated sand refers to porous materials composed of particles (or grains) weakly held together to form a solid but that can be easily broken when subjected to stress. These materials do not behave as conventional brittle, linear elastic materials and the transition between these two regimes cannot usually be described using poro-elastic models. Furthermore, conventional geotechnical sampling techniques often result in the destruction of the cementation and recovery of sufficient intact core is, therefore, difficult. This paper studies a numerical model that allows us to introduce weak consolidation in granular packs. The model, based on the LIGGGHTS open source project, simply adds an attractive contribution to particles in contact. This simple model allows us to reproduce key elements of the behaviour of the stress observed in compacted sands and clay, as well as in poorly consolidated sandstones. The paper finishes by inspecting the effect of different consolidation levels in fluid-driven fracture behaviour. Numerical results are compared qualitatively against experimental results on bio-cemented sandstones.
PubDate: 2022-05-12

• A Bayesian Approach for In-Situ Stress Prediction and Uncertainty
Quantification for Subsurface Engineering

Abstract: Abstract Many subsurface engineering applications require accurate knowledge of the in-situ state of stress for their safe design and operation. Existing methods to meet this need primarily include field measurements for estimating one or more of the principal stresses from a borehole, or optimization methods for constructing a 3D geomechanical model in terms of geophysical measurements. These methods, however, often contain considerable uncertainty in estimating the state of stress. In this paper, we build on a Bayesian approach to quantify uncertainty in stress estimations for subsurface engineering applications. This approach can provide an estimate of the 3D distribution of stress throughout the volume of interest and provide an estimate of the uncertainty arising from the stress measurement, the rheology parameters, and a paucity of measurements. The value of this approach is demonstrated using stress measurements from the In Salah carbon storage site, which was one of the world’s first industrial carbon capture and storage projects. This demonstration shows the application of this Bayesian approach for estimating the initial state of stress for In Salah and quantifying the uncertainty in the estimated stress. Also, an assessment of a maximum injection pressure to prevent geomechanical risks from CO2 injection pressures is provided in terms of the probability distribution of the minimum principal stress quantified by the approach. With the In Salah case study, this paper demonstrates that using the Bayesian approach can provide additional insights for site explorations and/or project operations to make informed-site decisions for subsurface engineering applications.
PubDate: 2022-05-12

• Stability of Spherical Cavity in Hoek–Brown Rock Mass

Abstract: Highlights A state of art approach to evaluate the stability of Hoek–Brown rock mass with a spherical cavity. Rigorous upper bound and lower bound solutions of stability factors are solved using advanced finite element limit analysis. Comprehensive design charts, tables and equations are presented for stability evaluation.
PubDate: 2022-05-09

• Investigate the Mode I Fracture Characteristics of Granite After
Heating/-LN2 Cooling Treatments

Abstract: Abstract Thermal treatment of the warm rock mass using liquid nitrogen (LN2) is a prospective rock fracturing technology in many geo-engineering applications. This paper presents an experimental and numerical work aimed at investigating the effect of thermal treatments (i.e., heating–LN2 cooling) on fracture failure characteristics. Mode I fracture toughness as a function of thermal treatment was determined using semi-circular bending tests. The roughness of the resultant fracture surfaces was quantitatively evaluated with a 3D laser scanner and fractal theory. Experimental results show that the thermal treatment has a significant influence on the fracture toughness and roughness. The fracture toughness of the thermally treated samples shows a negative correlation with the heating temperature, except in the range of 25–200 ºC where the fracture toughness shows a slight increase. However, the fracture roughness of thermally treated samples shows an opposite trend as it gradually increases with temperature. Scanning electron microscope analysis associates these phenomena to the development of thermal microcracks. Moreover, numerical simulations using the finite-discrete element method thermo-mechanical code (FDEM-TM) were conducted to reproduce the thermo/mechanical behavior of thermally treated rock, and to help explain the influence of the thermally induced microcracks on the failure mechanisms. The thermally induced microcracks contribute to the variation of the fracture toughness and roughness according to the laboratory experiment and numerical simulation. This work provides an improved understanding of the temperature effect on rock fracture characteristics in engineering applications.
PubDate: 2022-05-08

• Determination of Wave Propagation Coefficients of the Granite by
High-Speed Digital Image Correlation (HDIC)

Abstract: Abstract An experimental investigation of wave propagation coefficients determination of the granite was presented in the present study. Firstly, a series of pendulum impact tests were performed to investigate the stress wave properties of the granite. High-speed digital image correlation (HDIC) was utilized to capture the displacement and velocity at the free end of the impacted granite bar. Subsequently, the HDIC-based non-contact method was introduced for the determination of wave propagation coefficients of the granite. Finally, experimental studies based on the traditional contact method using strain gauges were performed to validate the present HDIC-based non-contact method. The results show that both the attenuation coefficient and wave number increase as frequency increases. Moreover, the propagation coefficients (attenuation coefficient and wave number) determined by the present HDIC-based non-contact method agree well with that determined by the traditional contact method using strain gauges. The present HDIC-based non-contact method can be used to predict the stress wave propagation through the granite effectively.
PubDate: 2022-05-08

• A Comparative Study of Point Load Index Test Procedures in Predicting the
Uniaxial Compressive Strength of Sandstones

Abstract: Abstract The point load index (PLI) test is one of the most frequently applied indirect methods in predicting the uniaxial compressive strength (UCS). Depending on the rock sample shape, the PLI test is performed in four procedures: axial, diametrical, block, and irregular lump tests. The present research aims to conduct a comparative study on the accuracy of these four procedures in predicting the UCS and evaluate the effect of density (ρ) and porosity (n) on the correlation between UCS and PLI. For this purpose, 15 different sandstone samples were collected from north Khorramabad, west of Iran. Some sandstone specimens were prepared for ρ, n, UCS, and PLI tests. Results indicated that PLI procedures have different accuracies in predicting the UCS, such that axial and irregular lump tests have the highest (R2 = 0.85) and the lowest (R2 = 0.70) accuracies, respectively. Moreover, the results of multivariate regression analysis revealed that n compared to ρ has a more important effect on the correlation between UCS and PLI (R2 = 0.87 and 0.92, respectively).
PubDate: 2022-05-05

• Rock Breakage and Tools Performance During Rock Processing by
Multidiameter Combination Saw with Different Diameters

Abstract: Abstract To better understand the rock breakage mechanism and optimize tool performance during rock machining by multidiameter combination saw, the rock processing experiment using a multidiameter combination saw was carried out on the bridge saw to investigate the variation of load with diameter in the combination saw. Furthermore, in this study, the sawing forces, tools wear, and rock breakage in the processing rock were qualitatively analyzed and compared. The experimental investigations demonstrated that the maximum undeformed chip thickness, the load per diamond, and the load in the sawing arc zone all decrease with increasing diameters of the single saw in the combination saw. The sum of the vertical forces of the single saw is generally less than that of the combination saw under the same parameters because of the existence of the coupling effect between the single saws. Different failure mechanisms of particles in the worn segment of the tool with different diameters also operate in rock processing using a multidiameter combination saw. With increasing diameter of saw blade, the proportion of the whole and blunt diamond particles increases, and that of the macro-fractured and pulled-out crystals decreases. Moreover, the differences in the surface integrity are attributed to the variation in the maximum undeformed chip thickness on the saw blade with different diameters in the combination saw and the gully depth on the surface, and the surface roughness of rock decreases with increasing diameter of the single saw.
PubDate: 2022-05-05

• Influences of Coal Seam Heterogeneity on Hydraulic Fracture Geometry: An
In Situ Observation Perspective

Abstract: Article Highlights The three-dimensional patterns of hydraulic fractures are presented with in situ underground observations. The coal body structure and coalbed structure greatly affect the hydraulic fracture geometry. Hydraulic fractures mainly develop in undeformed coal and weakly deformed coal. Weak layers and strongly deformed coal should not be perforated during fracturing engineering.
PubDate: 2022-05-05

• Experimental Study on the Mechanical Characteristics of Single-Fissure
Sandstone Under Triaxial Extension

Abstract: Abstract Generally, after excavation, a part of the rock slope or underground tunnel surrounding rock remains in a triaxial extension state. Meanwhile, the natural fissures in the rock mass are further expanded, which damages and destroys the rock. In this study, to investigate the mechanical properties and failure modes of single-fissured rocks under triaxial extension, single-fissure sandstone specimens with the same fissure length (l = 18 mm) but with different dip angles (α  = 0°, 30°, 45°, 60°, 90°) are examined under variable confining pressures (Pc = 0, 5, 10, 20, and 40 MPa) using an MTS815 testing machine and a compressive-to-tensile load conversion device. The results reveal that Pc has a significant effect on the failure strength of the single-fissure rock specimens. For a given dip angle, when Pc increases, the failure strength and axial deformation of the specimens increase moderately, and the failure stress gradually changes from tensile stress to compressive stress. Furthermore, the microscopic fracture pattern of the specimens also changes from intergranular fracture to transgranular fracture. The crack initiation angle gradually increases with the dip angle and Pc. The crack inclination of the specimen has a minor effect on the failure strength, except for Pc = 0.
PubDate: 2022-05-04

• Introduction to Selected Contributions from the 54th US Rock
Mechanics/Geomechanics Symposium, Golden, CO, 2020

PubDate: 2022-05-01

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