Abstract The plastic zone of the roof surrounding rock continues to expand after the coal seam mining. The permeability of the surrounding rock under plastic flow is a basic project for water inrush prevention in coal mine. In this work, the permeability experiments were carried out on roof sandstone from Xiaojihan No.2 coal seam under three loading paths. The variations of permeability affected by

Abstract The N00 mining method, as a novel coal mining technology, differs greatly in both the mining process and key technologies from traditional coal mining methods. To maintain entry stability under such new mining conditions, the stress and deformation process of the rocks surrounding the entry were analyzed based on the Mohr–Coulomb theory in this paper. The following results are concluded: the

Abstract The subsidence of offshore wells and platforms is a profound problem in the oil and gas industry. A new approach to reservoir geomechanical studies is used to analyze wellbore instabilities and investigate the subsidence of reservoirs. This study comprises an integrated workflow for developing a 3D geomechanical earth model for the North-Heera field, India. 1D Mechanical Earth Models are constructed

Abstract The physical and mechanical properties of surrounding rock of high level radioactive waste repository are affected by the heat released by nuclide decay. In this paper, the effects of temperature on P-wave velocity, porosity and tensile strength are investigated, the microstructure of the specimens with different temperature is observed utilizing a polarizing microscope. Brazilian splitting

Abstract Permeability is a fundamental index that is closely related to rock damage in geotechnical engineering. In this study, dynamic triaxial compression tests were performed using a modified split Hopkinson pressure bar (SHPB) for a range of incident energies, confining pressures, and number of impacts to study the mechanical behavior and permeability evolution of sandstone after dynamic loading

Abstract To eliminate roof-control disasters typically encountering in mines with thick and hard rock strata, fracture characteristics, instability mechanism and prevention methods were investigated in the study. A mine stope with thick and hard main roof and wedge-structure immediate roof in Zhuxianzhuang Coal Mine was taken as the background. In terms of the strata behaviors and roof control difficulty

Abstract Fault-slip induced by underground longwall mining could trigger dynamic failure to nearby mine openings. A better understanding of fault-slip behavior and the associated seismicity is significant for estimating the triggered damage and finding a feasible way to predict potential larger events. In this study, a displacement-dependent moment tensor method is introduced and embedded in the FLAC3D

Abstract The present study interpreted high-resolution aeromagnetic data using spectral analysis interpretation technique to carry out a regional estimation of geothermal resources of the entire Benue trough, Nigeria. The data was partitioned into 46 overlapping blocks and the depths to top, bottom and center of the magnetic sources for each overlapping data were computed. The calculated depths were

Abstract Abandoned roadways of coal mines are suitable for compressed air energy storage after proper treatment with grouting reinforcement and concrete lining. According to the theoretical analysis, the rock mass and concrete lining will experience cyclic tensile stress in the air injection-withdrawal process which is unfavorable to the long-term stability of the roadway. At present, few researches

Abstract Natural gas hydrate has great development significance and application prospect as a potential marine environment-friendly energy resource. It is difficult to exploit gas hydrate in deep-sea, and even causes serious marine geological disasters, such as submarine landslide. Mastering the mechanical behavior characteristics of gas hydrate reservoir is the crucial for safe and efficient exploitation

Abstract The fluid–solid coupled with triaxial servo-controlled seepage experiments of coal containing gas was used to study coal samples from a coal mine in Sichuan Province, China. The mechanical characteristics, seepage laws, energy dissipation, and fracture evolution of raw coal under incremental tiered cyclic loading and different confining pressures were studied. The experimental results show

Abstract Shock wave fracturing is a novel technology in coalbed methane (CBM) exploitation. Understanding dynamic damage and failure mechanisms of rock with different grain sizes is of vital importance to shock wave fracturing. In this study, we investigate the influence of grain size on the dynamic compressive strength and failure modes of sandstones under strain rates ranging from 20 to 100 s−1 and

Abstract Steering acid fracturing is a new way which can significantly increase oil and gas production. However, it is still unknown how to appropriately use steering acid in carbonate reservoir. Therefore, four true tri-axial acid fracturing experiments were carried out to study fracture initiation and propagation during steering acid fracturing. The experimental results reveal the following. 1. The

Abstract The shale gas potential of Ediacaran and Lower Silurian shales from the Upper Yangtze platform is assessed in this study with a focus on the contributions of clay minerals and organic matter to sorption capacity. For this purpose, a multidisciplinary assessment was carried out using petrophysical, mineralogical, petrographic and geochemical methods. In terms of TOC contents (4.2%), brittle

Abstract The Newark basin is one of the largest Mesozoic rift basins in Eastern North America, which preserves tectonic and climatic archives and has been considered for geologic CO2 storage. This paper describes geomechanical properties of the Newark basin formation, focusing primarily on mudstone intervals. Compressive strength, elastic moduli and acoustic velocities were evaluated with a series

Abstract With the development of society and the economy, the scale of underground cavern engineering is becoming increasingly larger. Unfortunately, underground cavern disasters such as roof collapse and rockburst occur frequently. Many studies have shown that the collapse of underground caverns is closely related to joints, which restricts the development of underground space and threatens the safety

Abstract Investigating the coupling effects of temperature levels and number of heating-water cooling cycles on thermal damage, cracking failure mechanisms, and mechanical responses of HDR (hot dry rock) is a vital issue during the exploitation of geothermal energy. In this study, a large number of granite samples exposed to high temperature treatment (25, 150, 300, 450, 600 °C) with multiple heating

Abstract Fatigue tests under high static pre-stress loads can provide meaningful results to better understand the time-dependent failure characteristics of rock and rock-like materials. However, fatigue tests under high static pre-stress loads are rarely reported in previous literature. In this study, the rock specimens were loaded with a high static pre-stress representing 70% and 80% of the uniaxial

Abstract Subdividing the reservoir sequences into some hydraulic flow units (HFUs) is one of the most serious challenges that face reservoir characterization and modeling in the oil industry. It may be a complicated process due to the heterogeneous nature of the hydrocarbons-bearing reservoirs, in particular in the case of non-clastic reservoirs. The stratigraphic modified Lorenz plot (SML) is one

Abstract Coal and lignite (brown coal) are geo-resources that govern energy production for decades. Geomechanical challenges, particularly slope stability, related to surface coal and lignite mines are critical during operation and determine the post-coal era. Several failure incidents have been reported in mining areas, typically associated with a sub-horizontal failure surface on a weak—clay or marl—layer

Abstract In the coal mining process, the limestone stratum under coal seams would be affected by high-pressure water, which has a significant influence on its physical and mechanical properties. To study the variation in limestone strength, uniaxial compression tests of three kinds of specimens processed with different water treatment methods are carried out, and the acoustic emission signals are collected

Abstract During the underground coal gasification process, a large amount of heat will be released, causing the surrounding rock in the goaf to undergo a high-temperature baking process. Therefore, it is essential to study the pyrolysis characteristics and mechanism of rocks. In this paper, the red sandstone in Linyi city of China is taken as an example. According to the results of thermogravimetric

Abstract The transport properties of complex fracture networks are of great significance to predicting the subsurface flow. Tree-like fracture networks were generated according to the fractal theory, and the roughness of fracture surfaces was created by using the Weierstrass–Mandelbrot function. The forward and reverse flows were numerically investigated via the lattice Boltzmann method by employing

Abstract Fault instability in response to subsurface wastewater injection is controlled by various operation- and site-dependent parameters. Previous numerical approaches focus on the prediction of the onset of fault reactivation, whereas the subsequent stress redistribution and fault movement are not considered. To better understand the potential correlation between injection activities and fault

Abstract Investigating analytical solutions to determine stresses for mine stopes with inclined walls is essential for the design of stopes in the mining industry, contributing to the prevention of serious accidents. Two variables in the analytical formula used for computing the vertical stresses in mine stopes with inclined walls play a vital role in the design. The two variables are the coefficient

Abstract Wave anelasticity of the fast P wave at mesoscopic scales is due to energy dissipation by conversion to slow P diffusive modes at heterogeneities much smaller than the wavelength and much larger than the pore size. We consider frames composed of two minerals and study the dissipation effects based on a generalized White plane-layered model, where the interfaces satisfy mixed boundary conditions

Abstract In unconventional natural gas development, the true triaxial stress field and anisotropic structure plane play an important role in the deformation and permeability evolution of reservoir rocks. In this research, the true triaxial experiments of sandstone, shale and coal with their own unique structural characteristics under the identical mean principal stress (p) and generalized shear stress

Abstract Determining rock damage thresholds is of great significance in predicting rock fracture. In this study, the relation among crack damage stress threshold (σcd), peak strength (σucs) and shape parameter m was observed. The impact imposed by temperature and confining pressure on m was then examined. The results show that there is an approximate linear relationship between σcd and σucs. Therefore

Abstract This work interprets the pore pressure distribution and in-situ stress magnitudes in the ~ 10,600 feet thick Neogene succession of the West and South Al-Khilala gas fields, onshore Nile Delta. The Messinian incised valley-fill (IVF) fluvio-marine sediments host the principal gas-bearing zones having a 0.47 PSI/feet pore pressure gradient, as seen from the downhole measurements. Early Pliocene

Abstract The slowdown of pressure solution creep has been thought to be caused by stress redistribution. This study presents a fresh view towards this creep behaviour. Basically, two rate-limiting mechanisms come into play amid pressure solution creep: (1) stress redistribution across expanding inter-granular contacts and (2) solute accumulation in the water film. Because non-hydrostatic dissolution

Abstract The evolution law of hydraulic fracture propagation and the fracture mode of two holes synchronous hydraulic fracturing under the influence of different factors were studied. Results showed that when the azimuth angle of two holes is 0° (θ = 0°), the stress at the center of the rock sample can be divided into three stages: the stress rising stage before crack initiation, the stress slowing

Abstract Understanding the depositional and development of hydrocarbon reservoirs is fundamental process to hydrocarbon exploration. Typically, water samples and remote sensing methods from existing or potential reservoirs can be used for interpretation of depositional environment. However, the lack of data in reservoirs represents a challenge for further exploration. The purpose of this study, the

Abstract In underground coal mining, the working face end is a bridge connecting the stope and the roadway. It not only is characterized by a large area pressure, but also faces the problems of rib spalling, roof falling, and floor heaving. In this research, a 3313 gob side entry retaining in fully mechanized top coal caving face in Shanxi Province was taken as the study object. First, by setting up

Abstract The mechanical characteristics of brittle materials submitted to combined compression and shear loading (CCSL) have received considerable attention recently. Both dynamic and quasi-static CCSL tests have been experimented to simulate the realistic working conditions encountered by different materials. Nevertheless, how the external shear loading affects the microcrack fracturing of rock still

Abstract Induced seismicity might occur during underground energy and resource exploitation. Seismic waves usually attenuate during propagation across rock joints. Joint surface configuration parameters such as the joint roughness coefficient (JRC) and joint matching coefficient (JMC) play an important role in affecting stress wave propagation and dynamic property. An experimental study was conducted

Abstract This paper simulates the propagation of hydraulic fractures under constant fluid pressure using the isogeometric analysis based on boundary element methods (BEM) i.e. the so called isogeomtric BEM. Due to the seamless integration between computer aided design (CAD) and numerical analysis, the isogeomtric BEM eliminates the meshing procedure and geometric errors, and explicitly parametrizes

Abstract The micro heterogeneities have a significant effect on the mechanical behaviour and failure mode of brittle rocks. In order to study the influence of microstructure and micro-mechanical properties on rock fracturing under blast loadings, a hybrid LS-DYNA and UDEC grain-based discrete element method (UDEC-GBM) is developed in this study. The LS-DYNA code is used to simulate the explosive detonation

Abstract Rock brittleness is an essential factor affecting underground engineering disasters and energy extraction. A large number of cracks are generated during rock destruction, and many acoustic emission (AE) signals are accompanied. The propagation speed and modes of cracks in different brittle rocks differ during failure, and their AE signals also show differing characteristics. In this study

Abstract Hard rock pillar is a crucial rock mass structure to maintain the stability of underground mine. It needs of special attention to analyze its stability from the point of rock mass quality. In this paper, the geological strength index (GSI) representing the rock mass quality of the hard rock pillar is examined as a new influence factor of stability, and combined with the conventional parameters

The rheological properties of rock are the main factors affecting the long-term stability of geotechnical engineering. However, the nonlinear rheological behavior in accelerating creep stage is still difficult to explain. In this paper, salt rock was used for triaxial compression experiments through incremental loading with different confining pressure. Determining the instantaneous elastic strain

Abstract We have developed a mathematical model by considering a buried, inclined, finite rectangular strike-slip fault in visco-elastic medium of Burger’s Rheology and the deformation caused in the medium is studied analytically. For modelling of deformations on the surface of viscoelastic half-space, the methods using the theory of dislocations are extended to calculate deformation inside the medium

Abstract Shear-related joint deformation is critical in the study of the anisotropic characteristics of a single rough joint in the ground stress field, such as aperture development within rock mass joints under the disturbance of mining construction, hydraulic transmissivity and permeability of gas in fractures in georesource research. However, natural rock specimens are too heterogeneous for laboratory

Accurate information of in-situ stresses is critical to all deep underground engineering. Unlike the vertical stress and minimum horizontal stress, the maximum horizontal stress cannot be directly measured, instead it must be inferred from other measurements. One widely used method is to inversely compute the maximum horizontal stress from borehole breakout angle revealed by caliper log or borehole

Traditional prediction methods for formation integrity collapse pressure are difficult to describe for shale microfractures, joints, and weakness planes. In this study, for multiple weakness planes, a reasonable prediction model for shale wellbore collapse instability is constructed using the Mohr–Coulomb criterion and the multistructural plane strength theory, which can analyze the wellbore collapse

Abstract This study presents resistivity and geomagnetic surveys to identify the subsurface structure of Tatta Pani geothermal spring, Kotli, Jammu & Kashmir, Pakistan. The flow, extension and subsurface structures were investigated using 1D resistivity survey by applying the technique of Vertical Electrical Sounding using Schlumberger electrode configuration. The data were then fed into iterative

Abstract A series of triaxial repetitive impact tests were conducted on a 50-mm-diameter split Hopkinson pressure bar testing device to reveal the characteristics of dynamic stress–strain of sandstone under confining pressure, and the confining pressure in this study was set as 5 and 10 MPa. The results showed that sandstone is very sensitive to confining pressure and strain rate. As the confining

Abstract Microwave-assisted rock fracturing has been widely applied to satisfy increasing demands for safety, high efficiency and energy saving. During microwave irradiation, rock damage occurs as a result of the irregular distribution of induced temperatures and resulting thermal stresses. This non-uniform temperature distribution may develop from either (1) intrinsic rock heterogeneity, or (2) from

Abstract The acoustic emission of hollow plate specimens of two calcitic marbles quarried in Greece is studied in the laboratory under uniaxial compression. Theses plate specimens are used as physical models, having a cylindrical opening of various sizes in the middle. Location analysis of the acoustic emission sources follows closely the macroscopic fracture surfaces, observed inside the collapsed

Monte Carlo simulation method is a powerful tool to consider inherent variability of soil properties in geotechnical problems. However, to fully reveal the variability and obtain convergent results, a large number of Monte Carlo simulations are required, which need great computational power and time, especially for complicated geotechnical problems with multiple random variables. In this paper, to

Abstract A pre-existing plane of weakness along the fault is comprised of a particular pattern of joints dipping at different orientations. The fault stress state, partially defined by the orientation of fault, determines the potential of slip failure and hence the evolution of fault permeability. Here the influence of fault orientation on permeability evolution was investigated by direct fluid injection

Abstract Characterizing the temperature-dependent shear mechanical responses of rock masses under constant normal stiffness (CNS) boundary conditions is of crucial importance for evaluating the stability and performance of deep underground projects. This paper experimentally analysed the shear mechanical properties and dilatancy deformation of sandstone exposed to high temperature with respect to various

Abstract The stability of surrounding rock is greatly affected by the mechanical properties of structural planes. At present, numerical methods have become an effective approach to scientifically evaluate the bearing capacity and predict the failure mode of jointed rock masses. Based on the basic theory of peridynamics, a strength reduction model is proposed to characterize the deformation and failure

Abstract Platy structures are a common geological feature in nature, and rock masses are often subjected to dynamic loadings. However, the dynamic behavior of rock plates has rarely been investigated. Three-dimensional FEM-based numerical modeling is used in this study to understand the cracking and failure characteristic of rock plates subjected to impact loading. First, a numerical plate center impact

The largest potential of geothermal energy lies in the hot granitic basement rocks with low permeability deep in the earth. Deep granitic rocks are usually exposed to the coupled water and thermal environment over a long period of time, as well as dynamic disturbance caused by drilling and excavation. Understanding the influence of low temperature water on rock is of great significance for effectively

Abstract A correlation study between the fracability and brittleness of shale gas reservoir is crucial for optimize reservoir reconstruction and enhance shale gas recovery. To investigate the relationship between fracability and brittleness of shale, a series of uniaxial compression tests of Silurian Longmaxi shale samples were carried out using a novel setup that combines X-ray micro-computed tomography

Abstract For the sustainability of lignite and coal mining, engineers need the soils' appropriate geotechnical characterisation of the excavations. This characterisation relates to the slope stability, the overall area stability, and the sustainable exploitation of mining areas during operational and post-closure eras. This work presents a novel perspective on the soil characterisation of lignite mine

Directional hydraulic fracturing by prefabricating longitudinal (axial) cracks on the sides of boreholes is an effective technique to control hard roof and ensure mining safety. In the present work, a true triaxial hydraulic fracturing experimental device was used to study the influence of prefabricated crack (pre-crack) parameters (including inclination angle and crack length), fracturing fluid viscosity

Abstract Due to differences in the properties of coal and gangue, gangue-containing coal often exhibits complex damage characteristics, which has become a key factor limiting the recovery rate in top coal caving. In order to improve the efficiency of top coal caving, it is necessary to recognize the failure mechanism of gangue-containing coal, especially the stress drop mode and the residual bearing

Abstract During the past decades, greenhouse gas mitigation techniques such as Carbon dioxide Capturing, Utilization, and Sequestration gained more attention due to the environmental concerns associated with the adverse impacts of global warming. Besides the feasibility of capturing and long-time storage of the CO2, it is of utmost importance to ensure longevity and safety of long-term CO2 storage

In an attempt to understand the general structural patterns of Ikogosi warm spring and environs, remotely sensed images have been integrated with high resolution aeromagnetic anomaly dataset. This is because subsurface faults offer pathways for the upward flow of geothermal fluids and imaging these structures where they are concealed provides localized areas for geothermal investigation. Interpretation