Subjects -> MINES AND MINING INDUSTRY (Total: 82 journals)
 Showing 1 - 42 of 42 Journals sorted by number of followers Stainless Steel World       (Followers: 18) Journal of Applied Geophysics       (Followers: 16) Journal of Metamorphic Geology       (Followers: 15) International Journal of Hospitality & Tourism Administration       (Followers: 14) Contributions to Mineralogy and Petrology       (Followers: 12) Journal of Geology and Mining Research       (Followers: 11) European Journal of Mineralogy       (Followers: 11) Mineral Processing and Extractive Metallurgy : Transactions of the Institutions of Mining and Metallurgy       (Followers: 11) Transactions of Nonferrous Metals Society of China       (Followers: 10) Journal of Human Resources in Hospitality & Tourism       (Followers: 9) Clay Minerals       (Followers: 9) Minerals Engineering       (Followers: 9) Lithos       (Followers: 9) International Journal of Minerals, Metallurgy, and Materials       (Followers: 9) Natural Resources Research       (Followers: 8) Geotechnical and Geological Engineering       (Followers: 8) Rock Mechanics and Rock Engineering       (Followers: 7) International Journal of Mining Engineering and Mineral Processing       (Followers: 6) International Journal of Rock Mechanics and Mining Sciences       (Followers: 6) Journal of Quality Assurance in Hospitality & Tourism       (Followers: 5) Mine Water and the Environment       (Followers: 5) Canadian Mineralogist       (Followers: 5) International Journal of Mining and Mineral Engineering       (Followers: 5) Journal of the Southern African Institute of Mining and Metallurgy       (Followers: 5) Mining Engineering       (Followers: 5) Applied Earth Science : Transactions of the Institutions of Mining and Metallurgy       (Followers: 5) Resources Policy       (Followers: 4) International Journal of Mining Science and Technology       (Followers: 4) Reviews in Mineralogy and Geochemistry       (Followers: 4) Mineral Processing and Extractive Metallurgy Review       (Followers: 4) International Journal of Mining, Reclamation and Environment       (Followers: 4) Physics and Chemistry of Minerals       (Followers: 4) Mineralium Deposita       (Followers: 4) International Journal of Coal Geology       (Followers: 4) Journal of Convention & Event Tourism       (Followers: 4) Geology of Ore Deposits       (Followers: 4) Mineralogy and Petrology       (Followers: 3) Rocks & Minerals       (Followers: 3) Journal of Sustainable Mining       (Followers: 3) International Journal of Coal Science & Technology       (Followers: 3) Lithology and Mineral Resources       (Followers: 3) Ghana Mining Journal       (Followers: 3) Mining Journal       (Followers: 3) Journal of Materials Research and Technology       (Followers: 2) Archives of Mining Sciences       (Followers: 2) Neues Jahrbuch für Mineralogie - Abhandlungen       (Followers: 2) Mining Report       (Followers: 2) Mining Technology : Transactions of the Institutions of Mining and Metallurgy       (Followers: 2) Environmental Geochemistry and Health       (Followers: 2) International Journal of Coal Preparation and Utilization       (Followers: 2) Mineralogia       (Followers: 2) Geomaterials       (Followers: 2) Journal of Mining Science       (Followers: 2) Extractive Industries and Society       (Followers: 2) Journal of Analytical and Numerical Methods in Mining Engineering       (Followers: 2) BHM Berg- und Hüttenmännische Monatshefte       (Followers: 2) CIM Journal       (Followers: 1) Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica       (Followers: 1) Gems & Gemology       (Followers: 1) Mineralogical Magazine       (Followers: 1) Rangeland Journal       (Followers: 1) Journal of Central South University       (Followers: 1) Natural Resources & Engineering Mining, Metallurgy & Exploration Podzemni Radovi Rudarsko-geološko-naftni Zbornik Journal of Mining Institute International Journal of Mining and Geo-Engineering Journal of China Coal Society Réalités industrielles Mineral Economics Minerals Gold Bulletin Minerals & Energy - Raw Materials Report
Similar Journals
 Rock Mechanics and Rock EngineeringJournal Prestige (SJR): 2.328 Citation Impact (citeScore): 3Number of Followers: 7      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1434-453X - ISSN (Online) 0723-2632 Published by Springer-Verlag  [2469 journals]
• Rockburst and Gas Outburst Forecasting using a Probabilistic Risk
Assessment Framework in Longwall Top Coal Caving Faces

Abstract: Abstract A probabilistic risk assessment framework was developed to mathematically represent the complex engineering phenomena of rock bursts and gas outbursts for a heterogeneous coal seam. An innovative object-based non-conditional simulation approach was used to distribute lithological heterogeneity present in the coal seam to respect their geological origin. The changing mining conditions during longwall top coal caving mining (LTCC) were extracted from a coupled numerical model to provide statistically sufficient data for probabilistic analysis. The complex interdependencies among abutment stress, pore pressure, the volume of total gas emission and incremental energy release rate, their stochastic variations and uncertainty were realistically implemented in the GoldSim software, and 100,000 equally likely scenarios were simulated using the Monte Carlo method to determine the probability of rock bursts and gas outbursts. The results obtained from the analysis incorporate the variability in mechanical, elastic and reservoir properties of coal due to lithological heterogeneity and result in the probability of the occurrence of rock bursts, coal and gas outbursts, and safe mining conditions. The framework realistically represents the complex mining environment, is resilient and results are reliable. The framework is generic and can be suitably modified to be used in different underground mining scenarios, overcoming the limitations of earlier empirical indices used.
PubDate: 2022-10-06

• Mean Cutting Force Prediction of Conical Picks Using Ensemble Learning

Abstract: Abstract The conical pick is the most essential tool of excavation machinery such as roadheaders, continuous miners, and shearers for breaking rock in mining and civil engineering operations. For rock cuttability, however, the geometry of conical picks and mechanical parameters of rocks are the most important factors. This study aims to construct an optimized data-driven predictive model to establish a quantitative correlation between strength of rock, geometry of tool, and cutting action data with the mean cutting force (CF). For this purpose, 157 datasets of 47 different materials including rocks, ores, coals, and artificial rocks with uniaxial compressive strength ( $${\sigma }_{c}$$ ), tensile strength ( $${\sigma }_{t}$$ ), cone angle ( $$\theta$$ ), attack angle ( $$\gamma$$ ), cutting depth ( $$d$$ ), and mean CF (MCF) are accumulated from the literature. Then, extreme gradient boosting (XGBoost) model is constructed by fine-tuning hyperparameters using grid search, random search, genetic algorithm (GA), particle swarm optimization (PSO), and differential evolution (DE). Based on performance indices that are calculated for each model, i.e., coefficient of determination ( $${R}^{2}$$ ), root mean square error (RMSE), and mean absolute percentage error (MAE) for the best performed model, i.e., DE-XGboost are $${R}^{2}=0.812$$ , RMSE = 2256.90 $$N$$ , and MAE = 1313.66 $$N$$ for training stage and $${R}^{2}=0.875$$ , RMSE = 2104.86 $$N$$ , and MAE = 1140.42 $$N$$ for testing stage, respectively. The findings also suggest that using a metaheuristic algorithm to fine-tune the hyperparameters of the XGBoost model can increase prediction accuracy. In the last step, three model interpretation methods viz., the permutation-based variable importance, H-statistic-based variable interaction, and accumulated local effects are applied to sensitivity analysis of the input parameters to predict MCF, providing key insights to model and researchers. The ALE plot demonstrated a complex non-linear relationship between predictors and the response variable. It is revealed that parameters $$d$$ and $$\theta$$ have the highest and lowest impact on the MCF, respectively. Finally, the successful implementation of this approach provides a solid platform for future studies and can be an alternative to complicated conventional and theoretical methods.
PubDate: 2022-10-06

• Hydraulic Fracture Vertical Propagation Mechanism in Interlayered Brittle
Shale Formations: An Experimental Investigation

Abstract: To investigate the vertical propagation mechanism of hydraulic fractures in interlayered brittle shale formations in the Qingyi member of the Southern Songliao Basin in Northeast China, an experimental model for simulating the shale within thin sandstone interlayers is designed. This model reflects the relative difference of the mechanical properties and brittleness characteristics between shale and sandstone. When combining a series of true triaxial hydraulic fracturing experiments with fracture area measurement, three-dimensional fracture reconstruction, and acoustic emission (AE) monitoring, the effects of the key geological and engineering factors on the fracture vertical propagation behaviors in interlayered shale formations are quantitatively studied. The experimental results showed four types of hydraulic fracture propagation patterns in interlayered shale formation: arresting pattern, deflecting pattern, penetrating pattern and composite pattern. The interlayer dip angle is negatively correlated with the penetrating ability of the hydraulic fracture, while the vertical in situ stress difference and interface cementation strength are positively correlated with the penetrating ability of the hydraulic fracture. The brittleness characteristics of the interlayer have a considerable effect on the propagation behavior of the hydraulic fracture. The interlayer with weak brittleness inhibits the hydraulic fractures’ ability to penetrate the interfaces and interlayers owing to the plastic deformation of the interlayer, thereby consuming considerably more elastic energy that should have been applied to fracture propagation. Under a higher injection rate and viscosity, the infiltration of the fracturing fluid in the interface is less, the hydraulic energy accumulated at the fracture tip is more concentrated, and the hydraulic fracture’s ability to penetrate through the interface into the interlayer is strengthened. The results of this study can provide a deeper understanding of fracture geometry and the fracture intersection mechanism in the continental interlayered shale formation, providing a more accurate guidance for fracturing parameter optimization.
PubDate: 2022-10-06

• A Limit Equilibrium Model to Simulate the Large-Scale Pillar Collapse at
the Everest Platinum Mine

Abstract: Abstract This paper is a case study of a large-scale pillar collapse at the Everest Platinum Mine. A major contributing factor to the collapse was the presence of weak alteration layers in the pillars. These alteration layers are found in the Bushveld Complex in South Africa where the pyroxenite layers have been exposed to hydrothermal fluid flow, serpentinisation and layer-parallel shearing. The resulting clay-like material and the weak partings substantially reduce the pillar strength. From the literature survey, it is clear that weak seams in pillars reduce their strength and conventional pillar strength formulas overestimate the strength in these cases. As an alternative, a novel numerical modelling approach is proposed to study the pillar failure and to conduct a back analysis of the mine collapse. This consists of a limit equilibrium constitutive model implemented in a displacement discontinuity code. Two areas of the mine were simulated, namely part of the collapsed area and a second area, with larger pillars that is still stable. This allowed for a preliminary calibration of the limit equilibrium model. The model illustrated that a reduction in friction angle on the partings, owing to the presence of water in the collapse area, seems to be a factor that contributed to the collapse. Although encouraging results are obtained, calibration of the limit equilibrium model remains a challenge. Laboratory testing is required in future to determine the strengths of the weak partings and in particular, the difference in strength of the wet and dry alteration zone material.
PubDate: 2022-10-05

• Experimental and Numerical Study on Tunnel Blasting Induced Damage
Characteristics of Grouted Surrounding Rock in Fault Zones

Abstract: Abstract The joint construction scheme of grouting reinforcement and blasting excavation is a highly efficient construction method for tunnels crossing soft, water-rich, and fractured geological zones. This paper focuses on the damage characteristics of the grouted surrounding rock induced by tunnel blasting. The variation law of acoustic wave velocity of grouted surrounding rock with the depth of each test hole was obtained by ultrasonic testing in the tunnel after blasting. By embedding the statistical damage constitutive model of rock mass based on stress criterion into the dynamic finite element code LS-DYNA, the damage of the surrounding rock under the influence of cyclic excavation blasting in the tunnel is analyzed. The damage distribution of the tunnel surrounding rock analyzed by numerical simulation is consistent with the damage distribution of the tunnel surrounding rock obtained by acoustic testing. The results show that the damage depth of the tunnel surrounding rock is 1.65 m ~ 2.79 m at the damage threshold of 0.19. The damage depth is 1.61 m ~ 2.69 m at the damage threshold of 0.28. Over the cross-section of the tunnel, the depth of damage is deepest at the bottom of the arch and shallowest at the foot of the arch of each bench of the tunnel. When the depth of damage to the surrounding rock is shallow, the degree of damage to the surrounding rock is large. When the damage depth of the surrounding rock is deeper, the degree of damage is generally smaller. The depth of damage is more than 2.5 m in the tunnel cross-section, within the range that needs to be reinforced. Finally, based on the depth of damage, the length of the anchors for the tunnel is proposed. Based on the distribution characteristics of the damage variables, a recommendation is made that the charge can be increased at the foot of the tunnel arch.
PubDate: 2022-10-05

• Reduction of Fragment Size from Mining to Mineral Processing: A Review

Abstract: The worldwide mining industry consumes a vast amount of energy in reduction of fragment size from mining to mineral processing with an extremely low-energy efficiency, particularly in ore crushing and grinding. Regarding such a situation, this article describes the effects of rock fragmentation by blasting on the energy consumption, productivity, minerals’ recovery, operational costs in the whole size reduction chain from mining to mineral processing, and the sustainability of mining industry. The main factors that influence rock fragmentation are analysed such as explosive, initiator, rock, and energy distribution including blast design, and the models for predicting rock fragmentation are briefly introduced. In addition, two important issues—fines and ore blending—are shortly presented. Furthermore, the feasibility of achieving an optimum fragmentation (satisfied by a minimum cost from drilling-blasting to crushing-grinding, maximum ore recovery ratio, high productivity, and minimum negative impact on safety and environment) is analysed. The analysis indicates that this feasibility is high. Finally, the measures and challenges for achieving optimum fragmentation are discussed. Highlights The effects of rock fragmentation on the whole size reduction chain from mining to mineral processing are described. The main factors influencing rock fragmentation by blasting are analysed. Main models for predicting rock fragmentation are briefly introduced and commented on. The feasibility, measures, and challenges of achieving optimum fragmentation are analysed.
PubDate: 2022-10-04

• Cracking Behaviors and Acoustic Emission Characteristics in Brittle
Failure of Flawed Sandstone: A True Triaxial Experiment Investigation

Abstract: Abstract True triaxial experiment with a synchronous acoustic emission (AE) monitoring system is a popular measure for the assessment of strength and cracking behaviors of brittle flawed rocks under anisotropic stress circumstances. This measure was employed to investigate the laboratory-scale brittle failure of flawed sandstone containing two different en echelon flaw configurations. Quantitative interpretations and comparisons of acousto-mechanical properties and cracking behaviors in intact and flawed sandstone have become available. Observations first revealed that en echelon flaws considerably weakened rock strength and deformability, and strongly affected the damage and failure processes. Second, intact specimen showed a quasi-2D spallation failure, while the failure of flawed specimens was dominated by the induced cracks initiated from en echelon flaws. Third, the two fundamental failure types of rock bridge including tensile-dominated failure and shear-dominated failure were registered. Whatever the failure type, micro-shear failure mechanism co-existed with micro-tensile failure mechanism. Moreover, AE amplitude distributions at the stable and unstable cracking phases follow a power law. The current findings provide insights into the brittle failure mechanisms of flawed rocks and have significant implications at scales relevant to seismicity and engineering applications.
PubDate: 2022-10-04

• Validation and Application of a Three-Dimensional Model for Simulating
Proppant Transport and Fracture Conductivity

Abstract: Abstract Hydraulically fractured well productivity greatly depends on fracture conductivity, which itself is dictated by proppant transport and placement. To guide engineering design and evaluate performance of proppant placement, a full understanding of the underlying physics and robust numerical models are needed. This paper introduces a continuum approach for simulating the transport of multiple fluids and proppant particles within hydraulic fractures. To achieve computational efficiency, this proppant model is developed based on the assumption of multi-component single phase flow and captures proppant settling, hindering effects, proppant-bed erosion and transport. Inter-particle stresses and collisions are not numerically calculated but represented through empirical correlations to include the effects of particle clustering and hindered settling. This model couples the fluid phase and particle phase through the slip velocity, which is governed by particle settling, particle–particle interaction and fluid-particle drag forces. The presented proppant model is validated by comparing numerical results with experimental data. With the calibrated simulation, the modeling capabilities on fracturing treatment design are demonstrated through sensitivity analysis and field-scale applications. Moreover, based on proppant placement and deformation, a generic model is applied to forecast fracture conductivity in different scenarios. As illustrated in this study, this coupled three-dimensional model is capable of simulating proppant placement and fracture conductivity under various operational conditions. This model can be broadly applied to improve fracturing design in various formations, including tight sandstone, shale, coal bed methane and carbonate reservoirs.
PubDate: 2022-10-03

• Effects of Axial Loading Width and Immediate Roof Thickness on the Failure
Mechanism of a Notched Roof in Room and Pillar Mining: Experimental Test
and Numerical Simulation

PubDate: 2022-10-01

• Correction to: Estimation of Brittleness Indexes from Petrographic
Characteristics of Different Sandstone Types (Cenozoic and Mesozoic
Sandstones), Markazi Province, Iran

PubDate: 2022-10-01

• Review of the Book “Convergence-Confinement Method for Tunnel Design”
by Marc Panet and Jean Sulem. Springer Tracts in Civil Engineering.
Springer

Abstract: Highlights A review of the book “Convergence-Confinement Method for Tunnel Design” is provided. The book is put in the context of tunnel design methodologies. The contents of every chapter are briefly summarized. A very positive assessment is eventually issued.
PubDate: 2022-10-01

• Cracking Behavior and Mechanism of Igneous Rocks Under Open-Ended

Abstract: Abstract Motivated by the potential field application of microwave-assisted rock breakage in rock engineering, microwave irradiation tests with open-ended applicators (hereafter surface irradiation) have been comprehensively carried out. In the present study, three kinds of igneous rocks were selected to conduct tests under different microwave conditions. The heating characteristics and cracking behaviors of the rocks under surface irradiation were obtained and the influences of rock and microwave conditions were analyzed. Furthermore, numerical simulations were conducted using COMSOL Multiphysics to obtain the temperature and stress distribution inside the rock. The results show that the highest surface temperature and the number, total length and maximum width of the cracks of igneous rocks increase with the microwave power level and duration. Under the same microwave condition, the diabase has the best heating characteristics and cracking behaviors, followed by quartz monzonite, and then alkali-feldspar granite. Dense crack zones within the irradiation area and radial cracks extending to the sample edges can be observed under surface irradiation. The dense crack zone is formed due to the differential expansion between minerals, while the generation of radial cracks is related to the circumferential tensile stress caused by the thermal expansion of the rock center.
PubDate: 2022-10-01

• Effect of Coal Fine Retention on the Permeability of Hydraulic Propped
Fracture

Abstract: Abstract The damage caused by coal fine retention to the permeability of hydraulic propped fractures is one of the key factors restricting coalbed methane (CBM) production. In this paper, permeability experiments of propped fractures under different coal fine retention conditions are carried out, and the retention coefficient of the coal fines is introduced. In addition, the permeability model of propped fractures is established to study the influence of constant rate flow and discontinuous flow on the coal fine retention, along with the influence of coal fine retention coefficient on the permeability of propped fracture in the single-phase flow drainage stage. The study results show that, with the increase of the coal fine flow rate, the retention of the coal fines decreases exponentially, in turn resulting in a logarithmic increase of the porosity and a logarithmic increase of the permeability in the propped fracture. The larger the coal fine particle size is, the likelier it is to remain, and likelier it is to reduce the porosity of the propped fracture, thereby resulting in a decrease in the propped fracture permeability. It is also shown that the retention coefficient of coal fines decreases exponentially with the increase of the flow rate, and increases with the increase of the coal fine particle size. In addition, the retention coefficient ratios of the two flow conditions increase linearly with the increase of the flow rate. The slower the flow rate is, the likelier the coal fines will be deposited in the constant rate flow; and the larger the flow rate is, the likelier the coal fines will be deposited in the discontinuous flow.
PubDate: 2022-10-01

• Mineral Composition and Grain Size Effects on the Fracture and Acoustic
Emission (AE) Characteristics of Rocks Under Compressive and Tensile
Stress

Abstract: Abstract The influence of rock mineral composition and mineral grain size on basic rock strength performance and AE characteristics have been studied, 13 different rocks microstructures are analyzed in an optical microscope thin section using petrographic image analysis, making it possible to determine the mineral composition and mineral texture characteristics of rocks. Then, the basic strength parameters of rock and AE signals generated during fracture propagation were obtained by UCT (uniaxial compression test) and BIT (Brazilian intension test). Finally, the relationship between basic strength parameters and AE characteristics of rock with mineral composition and grain size was analyzed. The results showed that different mineral constituents have significant effects on rock strength. The positive influence of plagioclase content on igneous strength was obtained. Sedimentary rocks strength increases initially and then decreases with the increase of plagioclase content. Besides, with the increase in quartz and K-feldspar content, the strength of the rock was weakened obviously. It is also found that the greater the dimensional deviation of mineral grain, the greater the strength of the rock. The strength of igneous rocks was inversely proportional to the mineral grain size, but there is no correlation between the sedimentary rocks strength and the mineral grain size. Furthermore, the tension–shear crack propagation of rock can effectively distinguish by judging that the data set of the AF–RA density graph was nearby the AF axis or RA axis and the peak frequency data sets of below 100 kHz or more than. Alterations in the rock nature are the main key reasons for the differences between AE hit rate, AE count rate, AE energy, and cumulative energy. The plagioclase content and grain size play a decisive role in AE signal characteristics and failure mode.
PubDate: 2022-10-01

• A Numerical Study on the Influence of Coordination Number on the Crushing
of Rockfill Materials

Abstract: Abstract Crushing of rockfill grains is one of the most important issues in the stability study of rockfill dams/embankments. In engineering applications, crushing characteristics of a rockfill grain depend strongly on its number of contact points with neighboring grains. The present work aims to propose a breakage criterion including the effects of coordination number, which refers to the increase of grain strength with the redistribution of stress towards hydrostatic stress conditions due to the continual crushing of neighboring grains. In order to analyze the influence of coordination number on grain crushing, single-particle crushing tests with different coordination numbers are first simulated by a bonded particle model using the discrete-element method (DEM). The mechanical confinement effects of neighboring grains are investigated by installing rigid walls around crushable agglomerates. One observes that the failure pattern and strength of agglomerates are significantly affected by the coordination number. The grain strength generally increases with increasing coordination number. Based on the results obtained at the grain scale, a new breakage criterion is proposed for rockfill materials. The proposed criterion is then embedded in a population balance model in DEM. The oedometer tests with three different grain sizes are simulated using the proposed criterion. In order to avoid the unrealistic mechanical response and reduce the energy accumulation in the particle spawning, a new numerical procedure is adopted in the simulations. The simulated stress–strain curve, normal compression line, and particle size distribution are in agreement with the experimental results. Comparison between the proposed criterion and some previous criteria illustrates the merits of the new criterion. The micro-responses of the samples, including the evolution of average coordination number and average particle stress, are also discussed. Discrete-element modeling and micromechanical analysis will enhance the understanding of crushing and deformation behaviors of rockfill materials.
PubDate: 2022-10-01

• Experimental and Numerical Impact Responses of an Innovative Rockfall
Protection Structure Made of Articulated Concrete Blocks

Abstract: Abstract This study deals with an innovative type of protection structure for gravity-driven natural hazards such as landslides (slope failures, rockfalls, etc.) consisting of a vertical wall made up of interconnected concrete blocks. This type of articulated structure presents many advantages including reduced footprint, versatility and easy maintenance. The response of such a structure under impact is investigated considering projectiles with kinetic energies of 520 and 1020 kJ, based on real-scale impact experiments and numerical simulations. The finite difference model is described in detail as well as the experiments. The model was developed focusing on the global structural impact response while keeping the computation time reasonable. The model parameter calibration is based on data in the literature and complemented with specific measurements. The experimental data allows us to describe the impact response of the structure and identify the main mechanisms controlling this response (sliding, tilting, and fracturing). The simulation results revealed that the model is efficient in mimicking this response, in terms of deformation amplitude and evolution with time. Finally, the numerical model made it possible to highlight complex mechanisms that were not possible to experimentally determine such as the different energy dissipation modes within the wall.
PubDate: 2022-10-01

• Triaxial Deformation of the Goldwyer Gas Shale at In Situ Stress
Conditions—Part I: Anisotropy of Elastic and Mechanical Properties

Abstract: Abstract The evolution of shale’s mechanical properties with confining pressure, temperature, and mineral composition directly influences fracture closure besides the effect of in situ stress variation across lithologies. We are the first to perform experimental study to characterize the mechanical properties of the Goldwyer gas shale formation located in the Canning Basin, Western Australia. We have performed constant strain rate multistage triaxial tests at in situ stress condition (confining pressure ≤ 22 MPa) on 15 samples of the Goldwyer gas shales with variable minerology, organic content, and heterogeneity. Deformation tests were conducted at room temperature and in drained conditions on cylindrical samples cored parallel (horizontal) and perpendicular (vertical) to the bedding plane. Both triaxial compressive strength (σTCS) and static young’s modulus E show a strong sensitivity to confining pressure and mineralogy, while only E shows a directional dependency, i.e., Eh > Ev. The internal friction coefficient µi in a plane parallel to the bedding is 0.72 ± 0.12, while it is only 0.58 ± 0.17 in the orthogonal direction. Both σTCS and E are significantly lower when larger fractions of weak mineral constituents are present (clays or organic matter). We observe that the Young’s modulus of most vertical samples is best approximated by Reuss’s bound, whereas that of horizontal samples is best approximated by Hill’s average of Voigt and Reuss bounds. The most prospective G-III unit of the Goldwyer shale formation (depth > 1510 m) is semi-brittle to brittle, making it suitable for future development.
PubDate: 2022-10-01

• Prediction of Uniaxial Compressive Strength Using Fully Bayesian Gaussian
Process Regression (fB-GPR) with Model Class Selection

Abstract: Abstract In rock, mining, and/or tunneling engineering, determination of uniaxial compressive strength (UCS) of rocks is an important and crucial task, which is often estimated from readily available index properties of rocks in practice, such as porosity (n), Schmidt hammer rebound number (Rn), P-wave velocity (Vp), point load index (Is(50)). This is especially true for projects with medium- or small-size, as well as for rocks with a high degree of fragility and porosity. While numerous methods have been proposed for predicting UCS indirectly, linear assumptions are frequently made during model development, despite the possibility of nonlinear relationships between UCS and the abovementioned indices. Furthermore, many established methods often struggle to strike a balance between model complexity and performance, resulting in models that are either over- or under-fitted. As a result, constructing an optimal UCS model with minimal variables while maintaining a high level of performance remains a great challenge in rock engineering practice. This paper proposes a fully Bayesian Gaussian process regression (fB-GPR) approach to develop an optimal model for UCS prediction which strikes a balance between prediction accuracy and model complexity. Both real-world and numerical examples are used to illustrate the proposed method. Results show that the optimal model of predicting UCS for the database from Malaysia is constructed by only n and Vp, with the same coefficient of determination of around 0.9 as the more complex model involving n, Rn, Vp and Is(50). A sensitivity study is also performed to systematically examine its robustness and accuracy of the proposed method in developing optimal model for UCS prediction.
PubDate: 2022-10-01

• Simulation of Brittle Failure Around Canada’s Mine-By Experiment Tunnel
Using 2D Continuum-Based Voronoi Tessellated Models

Abstract: Abstract The failure process of brittle rocks under compression involves the initiation, accumulation and propagation of tensile fractures before peak stress is reached. This process is influenced by the internal microstructure and the presence of heterogeneities in rock, creating localized concentrations of tensile stresses. A realistic simulation of this process requires an explicit representation of rock heterogeneities. The Voronoi tessellation technique is commonly used in numerical methods to simulate heterogeneities in brittle rocks. In this approach, the model domain is divided into several randomly generated polygonal Voronoi blocks separated by numerical ‘joint’ elements. This modelling approach is referred to as a Voronoi Tessellated Model (VTM). Discontinuum-based VTMs provide a better representation of the brittle rock failure process compared to conventional continuum methods. However, their higher computational costs may limit their practical applicability. In this study, a continuum-based VTM was developed using a two-dimensional finite element program to simulate the failure of Lac du Bonnet granite under laboratory and field loading conditions. For this purpose, the VTM with inelastic blocks and block boundaries was first calibrated to the intact (undamaged) rock strength obtained from laboratory tests and then to the rock mass strength estimated based on a tri-linear, brittle failure criterion. The calibrated VTMs were then used to simulate the brittle failure around a circular test tunnel at Canada’s Underground Research Laboratory (URL). As expected, the model calibrated to the intact rock strength did not capture the observed failure; however, the VTM calibrated to the tri-linear criterion did successfully replicate the observed V-shaped notch failure and damage zone around the test tunnel.
PubDate: 2022-10-01

• Investigation into Rock Breakage with Expansive Cement Under Biaxial
Confinement

Abstract: Abstract While drilling and blasting with explosives is widely used for rock fragmentation in mining and civil engineering, its use is associated with rigorous safety and environmental constraints as blasting creates toxic fumes, vibrations and dust. In recent years, there has been a growing interest in transitioning from blasting with explosives to rock fragmentation without explosives. In this study, the potential of expansive cement (EC), aka soundless chemical demolition agent (SCDA), as an alternative to explosives to break hard rock under confinement is explored through a comprehensive experimental and numerical modelling study. To do so, two large-scale tests have been designed and carried out on 1 m × 1 m × 0.25 m panels made from high-strength concrete and subjected to planar, biaxial loading conditions. Such test configuration is designed to mimic a mining front subjected to biaxial stresses. Different EC drill hole patterns were tested and compared. The fragmentation behaviour due to EC was first examined with five particle flow code (PFC2D) models simulating different EC drill hole patterns. Two panel designs were retained for the large-scale experiment. It is found that rock breakage with EC under confinement is feasible and promising, especially when the optimized drill pattern from numerical modelling is adopted. It is demonstrated that discrete element modeling with PFC2D can be used effectively to design and optimize the EC drill hole pattern under biaxial confinement. The findings of this study could set the stage for numerous future applications of EC for rock fragmentation of subsurface hard rock excavations such as shafts, tunnels, and mine openings.
PubDate: 2022-10-01

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