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

Seismic activities have been reported by the large-scale fluid injection in shale reservoirs both during hydraulic fracturing operations and wastewater disposal processes. Fluid overpressure has been regarded as the primary cause for the injection-induced seismicity since the fluid lubricates the fault and decreases the effective normal stress applied to the pre-existing faults. However, how fractures/faults

The weak bedding sandwiched between rock layers is one of the crucial factors influencing the overburden failure with the extraction of coal resources in longwall mining. In this article, the physical model tests and discrete element modelling (DEM) were carried out to examine the effects of bedding adhesion strength (BAS) on the roof fracture with longwall coal mining. A novel model generation method

Granite at a high temperature can cause a decrease in strength and cracking when exposed to a rapid cooling shock. Therefore, the cooling shock method can be considered as a potential cracking technology to improve the energy exploitation efficiency. The thermal cracking damage of high-temperature granite after cooling shock induced by different low-temperature refrigerants were studied. Firstly, granite

In this study, the stress change of a rock mass in front of the working face during underground excavation was simulated. The effect of loading and unloading rates on the mechanical characteristics, strain energy, and failure mode evolution of the sandstone were investigated. It was found that the loading rate of vertical stress had little effect on the varying trend of the volume strain, and the volume

Segmental lining is a new supporting structure for mine tunnels, but the applicability of the existing protective coal pillar design method to this structure is uncertain. In this paper, based on TBM-inclined tunnels in Xinjie Coalmine, China, a 1:35 scale 2D physical model with a 4 m width and 1.8 m height was constructed to simulate the complete engineering process. The effects of coal mining on

The bedding orientation influences the failure pattern and brittleness of shale. Clarifying the relation between acoustic emission and the effects of bedding orientation on the failure behaviors of shale is important to understand the mechanism of the formation of fracture networks. In this study, we analyzed the failure patterns and crack complexity of the shale specimens with various bedding orientations

The development of micro-cracks during damage to rocks affects the propagation of macroscopic cracks on the surface. To explore the crack evolution among pre-existing flaws in rocks, based on the acoustic emission (AE) source location results, the paper analysed the influences of micro-crack development on failure mode. By analyzing AE characteristic parameters, the main controlling factors affecting

The effect of high temperature on engineering properties of rocks has recently become an important topic for geotechnical engineering applications due to the development in geothermal energy extraction, underground coal gasification, disposal of nuclear waste and deep mining applications. This study aims to investigate the engineering properties of four rocks heated at high temperatures and to identify

The existence of a deep borehole in the Earth’s crust disturbs the local stresses and creates a stress concentration that may result in breakout and damage to the borehole. Maintaining wellbore integrity mitigates environmental impacts such as groundwater contamination, gas leakage to the atmosphere, and fluid spills and seepage at the surface. In this paper, the stability of deep boreholes (5 km)

A simulation was performed of the electromagnetic fields response to different unconventional reservoir scenarios and transmitter to receiver configuration, including strong anisotropy, combination of anisotropies and geometries, and larger monitoring times than conventional ones. The approximate solution of the anisotropic Maxwell equations was obtained using a mixed finite element method, discretized

A large fault fracture zone with about 100 m wide exists in Wuyue Pumped Storage Power station of China, where the low-strength and highly-fractured granite severely restricts the stability of the underground powerhouse. However, no relevant exploration has been made on its lithology to ensure the safety of the upcoming construction. To overcome this insufficiency, we present the most recent researches

The dynamic behaviors of calcareous sand were investigated under undrained conditions using cyclic triaxial tests, and the results were compared with those of commercially available Fujian (Fj) sand. The test results were used to evaluate the effects of gradation, particle crushing, and other parameters on the liquefaction resistance. The results of the undrained cyclic triaxial tests indicate that

A gravel cushion is an effective method for preventing rockfall disasters, but the thickness and particle size of cushion influence the impact response between rockfall and cushion. Based on previous indoor experiments, a numerical model of a rockfall impacting a cushion was built, and the accuracy of the model were verified by comparing with the coefficient of restitution obtained from experimental

During infrastructure construction and resource exploitation, the stability analysis of the working face and the determination of the limit support pressure are important. Herein, an improved wedge-prism model is proposed with consideration of three aspects. The inter-slice vertical force expression at any depth in the prism is derived using the slice method, and the vertical force acting on the wedge

In situ capture of crack network evolution is extremely difficult but necessary in fundamental research on mining mechanics and coalbed methane extraction. Systematic field monitoring of the mining-induced crack networks near three mining faces with vertical depths of 700 m, 850 m, and 1100 m in the Pingdingshan coal mine in China was conducted. By utilizing fractal geometry and an algorithm that predicts

Mastering the damage evolution and gas–solid coupling behaviours of coal containing gas allows for the in depth recognition of underlying coal and gas outburst mechanisms. In the current study, we derive an expression for the damage factor of coal containing gas based on the theory of energy conservation to monitor the evolution law of the damage factor during the entire stress–strain process. Under

To investigate the connection and bifurcation problems of the propagation principle and behavior in the whole process of rock crack, bulk insert of cohesive elements between entity elements has been developed. First, it defines what kind of cohesive element is best to be inserted between the model elements. To minimize the influence of embedded cohesive elements on the overall stiffness, Kcohesive

Intermediate geotechnical materials such as Victorian Brown Coal (VBC) often exhibit complex fracture characteristics due to the interplay of ductile and brittle behaviour. A diverse set of in situ joint orientations and fracture characteristics are found in the open-cut mines of the Latrobe Valley, Victoria, Australia. As such, the propagation of pre-existing discontinuities plays a significant role

As an emerging numerical calculation method, the numerical manifold method (NMM) has incomparable advantage in solving continuous and discontinuous deformation problems in a unified framework. In this study, an improved numerical manifold method was deployed to solve the crack propagation and coalescence problem with cracking friction effect in fractured rock mass. Firstly, based on the basic theory

The stability of slopes directly affects human lives, the environment, and the economy. Inaccurate geological profiles within numerical slope stability models can lead to potentially catastrophic consequences when model conditions do not appropriately reflect real-life stratigraphy. In cases where localised deposits are prevalent, probabilistic methods are often necessary to accommodate for unknown

Multiple hydraulic fracturing treatment from horizontal wells has been widely used to enhance the productivity of unconventional hydrocarbons. Interaction among the fractures can cause the reorientation of fractures and lower the stimulation efficiency. We perform discrete element method (DEM) simulations to assess the influence of completion scheme on the trajectory and efficiency of fractures si

Selective breakdown of mineralized particles by using high-voltage pulses (HVP) has been reported, yet its mechanisms are not fully understood, and the HVP setting factors affecting its efficacy in ore pre-concentration for the mining industry are not established. This study investigates the electro-dynamic mechanisms of electric breakdown by using the time-transient dielectric breakdown model and

Hard roof fracturing characteristics and mining-induced stress behaviors can be studied to ensure production safety in top coal caving face. Field tests were conducted at top coal caving face No. 8309 in the Tongxin mine of the Datong Coal Mining Group in China. The monitoring results indicated two modes of periodic weighting: short weighting steps with low intensity and long weighting steps with high

The determination of the gray threshold is crucial for the quantitative characterization of digital images. In this study, a new algorithm is proposed to determine the optimal image segmentation threshold. This algorithm is based on a combined analysis of the gray distribution curve and its second differential distribution curve of the digital image. Then, the feasibility and accuracy of the Liu–Cao

The dynamic mechanical behavior of jointed rock mass plays a key role in the blasting excavation from mining and tunneling engineering. To investigate the influence of joint parameters (e.g., joint length, joint position and joint type) on the mechanical behavior of singly-jointed samples, dynamic impact compression tests are performed on prefabricated rock-like samples using the Split Hopkinson Pressure

The mechanical properties and permeability of shales after supercritical carbon dioxide (SC-CO2) imbibition are vital to shale gas production and CO2 sequestration in shale reservoirs. In this study, triaxial compressive strength tests, steady state permeability tests, and CT scanning tests are performed on shale samples with 30 days of SC-CO2 imbibition. The results show that minerals dissolution

The mesoscopic parameters of numerical simulation cannot be directly obtained from laboratory test, and it is necessary to calibrate the parameters by comparing the numerical simulation results with the experimental results. To quickly and reasonably determine the mesoscopic parameters of limestone, a unique variable principle is used to comprehensively analyze the quantitative relationship between

Supercritical carbon dioxide (SC-CO2) jet is a promising technology for the extraction of coalbed methane. As a key component in the process of jet formation, the nozzle is an essential factor affecting the efficiency with which an SC-CO2 jet breaks coal and rock. The nozzle structure directly affects the energy conversion rate and flow field structure of the jet. Thus, the use of a suitable nozzle

Low cutting rate and high tool wear are the important problems during excavating hard rocks. In order to find a solution for these problems, some investigations have been carried out by several researchers. One of the recent studies is the microwave assisted excavation of hard rocks. Revealing the impacts of microwave exposure on the minerals and micro-structures of rocks will be useful for the investigations

For more than seven decades, the impounding of artificial water reservoirs has been known to trigger earthquakes. Accordingly, reservoir-induced seismicity (RIS) has been studied in terms of its identification and mechanisms. In this paper, we report three laboratory experiments to investigate the effects of water impoundment and pore-pressure diffusion on the reactivation of faults in high tectonic