Multiseam mining in gully regions has resulted in severe and complex disaster chains, including crack development, mountain landslides, river blockage, and intensified mine water inflow. To prevent and control water inrush disasters, it is imperative to investigate the characteristics and mechanizations of overburden failure under the combined effect of gully terrain and repeated mining in coal seams

We conducted small-scale field hydraulic fracturing (HF) experiments using carbon dioxide (CO2) and water as fracturing fluids. A hole was drilled 10–14 m below the tunnel floor into hot granitic rock whose temperature can form CO2 supercritical state at HF pressure. Under the same injection rate of 10 mL/min, the volume of the acoustic emission (AE) hypocenter distribution induced by CO2 HF was approximately

The intermediate effective principal stress has a considerable influence on rock strength as shown by true-triaxial data on intact rock. Therefore, a failure criterion that incorporates all three principal stresses may provide an improved prediction of failure than one that considers only the major and minor effective principal stresses. This study introduces a generalisation method, which converts

In the current paper, we propose a new three-dimensional strength criterion for rocks expressed in terms of the first principal stress invariant, I1, and the second and third invariants of the deviatoric stress tensor, J2 and J3. The design of this constitutive model conjugates the characteristics of two of the most well-known and widely used criteria in geotechnical engineering: Hoek-Brown and Matsuoka-Nakai

Tensile fractures in brittle materials may exhibit striation features running along the surface that indicate the trajectory of fracture propagation. Because of the directional persistence of these features, directional roughness characterization methods can be used on subsampled fracture surface data to map localized roughness features that follow these striations. These maps can aid in the interpretation

Granite for hosting the deep geological repository (DGR) is subjected to thermo-hydro-mechanical (THM) treatment for decades of years, while the variations in the tensile strengths of mineral grain interfaces (MGIs) with THM treatment are still unknown. Served as an important parameter in determining the macro mechanical properties of granite, quantifying the tensile strength degradation of MGI with

Clear understanding of overburden failure propagation during underground mining is critical in managing safety and environmental issues such as rock burst hazards, groundwater inrush and longwall convergency. This paper presents an in-situ monitoring study of overburden strain dynamics at a kilometre-deep longwall mine using distributed fibre optic sensing technology (DFOS). A deep borehole was drilled

The effect of blasting vibration on the macroscopic failure characteristics of underground tunnels has been investigated, but little attention has been paid to the stress and deformation characteristics of underground tunnels under the combined action of explosion waves and in-situ stresses. Consequently, enhancing the bearing capacity of surrounding rock masses by adopting effective reinforcement

Surface defects are prevalent in natural rock masses, and the newborn cracks that initiate from these defects and significantly affect structural stability usually extend in a three-dimensional (3D) manner. Hence, in this research, a series of uniaxial compression tests were conducted on sandstone specimens containing a surface flaw to examine the effect of nondimensional flaw depth (0, 0.3, 0.5 and

Analytical description of the process of rock discontinuity caused by the operation of an experimental cutting head, in which a combination of cutting and loosening methods was used, is presented. Loosening of the rock fragment takes place after reaching the tensile or shear strength of the rock, what is more favourable compared to the classical mining methods. An analytical model of the stress in

Strain rockburst poses a great threat to the construction safety of deep engineering, especially induced by dynamic impact loads such as blasting from the adjacent tunnel excavation. Aiming to clarify the failure characteristics and mechanism of strain rockburst induced by the dynamic impact load, a series of dynamic impact tests under different biaxial prestress conditions were conducted on the sandstone

Clay shales are low-permeable sedimentary rocks that exhibit inherent cross-anisotropic stiffness, strength, and permeability. Accurate design of tunnels excavated in clay shales requires appropriate constitutive models that account for the anisotropic properties of the host rock, especially under undrained conditions. This paper presents a transversely isotropic elastoplastic-damage model for fully-saturated

Heterogeneity is an inherent feature of subsurface rocks. Unconventional reservoir shales, a group of typically fined-grained sedimentary rocks, usually exhibit strong heterogeneities due to the diversity of their constituents, including stiff silicate and carbonate minerals, ductile clay minerals, and organic matter. Understanding the influence of heterogeneities on the mechanical response as well

Understanding the scale effect in the behavior of solid materials is important when small-scale models are used to predict the behavior of real structures. Tremendous efforts have been devoted to investigating the scale effect in the strength of quasi-brittle materials. However, limited studies have focused on the whether there is a scale effect in bursting failure, which is a typical failure pattern

This study investigates the propagation and attenuation characteristics of shock waves produced by drilling and blasting. The focus is on a novel method for calculating the attenuation of the shock wave pressure. Based on the propagation of shock waves in a rod with a variable section and a Maxwell model for rock, theoretical solutions for the attenuation of the blast-induced shock wave pressure were

The thick and steeply inclined coal seams of the Junggar Basin of Xinjiang, China, are unique with dip angles generally >50° but over the range 0°–85°. Initial and evolving permeability and pressures change drastically around wells down-dip within the steeply inclined reservoir as a result of the depth differential. Hence, the evolution of permeability and fluid pressures during drainage exhibits significant

Acoustic emission (AE) technology is widely used to monitor the damage evolution of rock. Identifying AE signals is crucial to reveal the rock cracking mechanism. The current tension and shear signal discrimination methods primarily rely on AE parameters. However, the differences between AE parameters and waveform images used as inputs require further exploration. Acoustic emission data from Brazilian

We propose a novel method for studying the λ/μ ratio, the vP/vS ratio and Poisson's ratio of rocks based on the determination of highly accurate moment tensors of acoustic emissions (AEs). The validity of the method is verified on observations of 539 AEs recorded in a sandstone sample during a semi-circular bend test. We show that the sandstone exhibits the so-called bi-modular behaviour indicating

To reveal the size effect and lateral pressure effect of columnar jointed basalts (CJBs), the meso-damage mechanics, statistical strength theory, continuum mechanics and digital image correlation are combined, and a series of heterogeneous numerical models of CJBs orthogonal and parallel to column axis are established. The elastic modulus, Poisson's ratio, uniaxial compressive strength, friction angle

Borehole breakout is a natural phenomenon resulting from in-situ stress redistribution around a borehole, and its orientation and geometries are critical indicators for in-situ stress direction and magnitudes. The aim of the study is to better understand the borehole breakout formation mechanism and reproduce breakout geometries using numerical simulations. A 2D bonded-particle model (BPM) is developed

Various numerical methods have been developed for modelling rock fracturing problems. Most of the available studies could reproduce reasonable results for given experimental data, but the ability and accuracy of these methods to predict rock fracturing are still controversial, and a systematic comparison is lacking. In this study, a set of rock mechanics experiments were designed for a numerical modelling

Rockburst in deep rock engineering poses serious threat to personnel safety and engineering. In order to reveal the rockburst characteristics in deep engineering, the rockburst investigations and rockburst mechanisms based on in-situ stress were carried out at five deep gold mines in Jiaodong Peninsula, China. At the cover depth between 400 m and 600 m, the ground pressure hazards are mainly local

Creep of shale controls the stability of fault gouge in sedimentary rocks, aseismic deformation in the upper crust, and several engineering operations, such as proppant embedment, reservoir subsidence, and wellbore stability during unconventional shale gas exploitation. However, measuring the creep properties of shale is challenging due to the multi-scale structure of this rock. Here, our goal is to

The caving mining method relies on gravity to transport large amounts of caved ore and rock, therefore, the gravity flow rules are the foundation for determining or optimizing the stope parameters. The stochastic medium draw theory of gravity flow is relatively fast and easy to implement, and it can describe different shapes of the drawbody. However, the theory usually regards the drawpoint as a point

This study focuses on rock damage potentially developing in the near-field of a planned underground nuclear waste repository at the Forsmark site (Sweden). In hard, crystalline rocks, mechanical damage in the form of spalling may be induced during construction by overstressing of the excavation periphery. During operation, thermal damage may develop due to additional thermo-elastic stresses forming

Abstract not available

In this paper, the governing equations of non-isothermal two-phase flow in unsaturated, deformable porous media are presented based on different representations of the gaseous phase along with their implementations in the open-source FEM code OpenGeoSys 6. As one implementation utilises the Richards equation to represent the unsaturated system whereas the second implementation relies on a two-component

Decoupled charge structures are widely used in contour blasting because of their lower peak value and loading rate of the borehole wall pressure (BWP), which plays an important role in the contour blasting effect. The filling medium and decoupling ratio are the two key factors of decoupled charge blasting, and their effects on the peak value, rise time and loading rate of BWP need to be investigated

A coupled numerical framework based on smoothed particle hydrodynamics (SPH) and finite difference method (FDM) has been developed to analyze the coupled process of fluid flow in a deformable poro-elastic medium. The salient feature of the developed coupled model is that the porous media has been simulated by two separate layers to describe solid and fluid phase with their respective governing equations

Brittle-ductile transition conditions and mechanisms are key scientific issues embedded in the reservoir deformation-related difficulties faced during shale gas exploration and exploitation. In this study, shale deformation experiments under different temperatures, confining pressure and differential stress were conducted using a NaCl solid confining pressure medium, taking the Lower Silurian marine

Rockfall events represent a serious hazard for people, structures, and infrastructures. The phenomenon can occur in several environments, natural and artificial. In surface mining operations, blasting, bench clean-up and scaling can induce rock blocks detachment, compromising operators’ and operations’ safety. The installation of passive mitigation measures coupled with a specific design of the pit

Numerical simulations become a necessity when experimental approaches cannot cover the required physical and time scale of interest. One of such area is a simulation of long-term host rock behaviors for nuclear waste disposal and simulation tools involved in the assessment must go through rigorous validation tests. The DECOVALEX project (Development of COupled models and their VAlidation against EXperiments)

We model the full wavefield produced by a seismic velocity survey and optimise the representation of the fracture zone to best match field waveforms. The velocity survey was part of a mapping study on fractures in the Excavation Damage Zone (EDZ) of ONKALO underground research facility at Olkiluoto. The EDZ results from excavation of the rock mass, which modifies stress conditions changing the nature

The safe and efficient development of ultra-deep shale gas deeper than 4500 m is closely related to the comprehensive evaluation of the mechanical behavior, brittleness and anisotropy characteristics of reservoir rocks under in-situ stress conditions. However, the above-mentioned information about ultra-deep shale is rarely reported. This study aims to fill this gap by systematically investigating

A natural rock often has a positive Poisson's ratio during compression. However, the thermal-damaged rock can abnormally present a negative Poisson's ratio. Thus far, the related mechanism has not been fully clarified from a micromechanical viewpoint. Here, we established a grain-based model to characterize the negative Poisson's ratio effect of the thermal-damaged crystalline rock using the universal

An airblast is a sudden collapse of a large volume of rock that causes air to rapidly flow through an underground opening as a result of air being compressed in a small space. Through the solution of the Ergun equation for turbulent flows in porous media, we have modeled air gusts in this paper. To resolve the issue, we use the finite element method (FEM). At a drawbell’s associated drawpoints, air

We study the role of in-situ stresses in fluid flow and mass transport through a two-dimensional fractured rock. The fracture network is based on a real outcrop with a connectivity state around the percolation threshold. We simulate stress-dependent fracture propagation and deformation using a geomechanics model based on the hybrid finite-discrete element method. The hydrodynamic transport through

The presence of joints dramatically affects the mechanical behavior of rock mass. For highly fractured jointed rock mass, it is more convenient to treat the jointed rock mass as equivalent continuum material. Consequently, several researchers have proposed continuum models to describe the mechanical behavior of jointed rock mass. These models are reviewed and their limitations are discussed. From the

This study revisited a well-founded analytical solution describing the collapse profiles of tunnel roofs and estimated traditional stability measures to be used for quantitative safety assessment and practical engineering design. The original analytical approach was proposed by Fraldi and Guarracino based on a variational approach in the context of limit analysis, and subsequently extended to account

The influences of surface roughness and shear processes on fluid flow and solute transport through three-dimensional (3D) crossed rock fractures, a vital element of fracture networks, were systematically investigated. Surfaces of tensile fractures created by splitting granite and sandstone samples along its two orthogonal central axes were optically scanned to generate rough-walled crossed fracture

High-frequency components in acoustic emission (AE) or seismic radiation attract much attention as they are directly related to the fracture process. One of the main issues in our knowledge of high-frequency radiation is a lack of definition on the relationship between high-frequency content and source mechanisms. In this study, high-frequency emission waves due to rock fracture in tension and shear

Reliable prediction of the rate- and fluid-dependent evolution of elasto-plastic strain in chalk is essential to minimize the risk associated with sea-floor subsidence and subsurface deformation. Experimental observations show that physicochemical interaction between the aqueous solutions and rock surface causes the change of mechanical properties in chalk. Here, we quantify the experimental observations

The natural fracture system exerts a significant influence on the physical and mechanical properties of rock masses. The heat transfer in fractured rock masses is much more complicated than that of intact rock due to the thermal contact resistance induced by natural fractures with varying size, aperture, roughness, and orientation. This work describes a method for determining the representative element

To bolster the safety and efficacy of blasting and impact drilling for underground works in composite rock strata, the dynamic tension of composite rocks requires thorough examination. Given the challenges of composite rock sampling, cement mortars with varying mix ratios are utilized to create composite rock-like test blocks. These blocks are composed of two different strength materials, further processed

The relative permeability curve is one of the key features to evaluate the flow property of a porous medium, which is important in petroleum and gas industry, yet it is not easy to obtain. In this study, we proposed a new intelligent way to predict the relative permeability curves directly from 3D digital rock images, compared with other existing artificial intelligence (AI) methods that usually used

In caving mines, productivity and safety can be affected by geotechnical hazards, such as rockbursts, inrushes, collapses, and air blasts. These operational risks decrease the availability of drawpoints and impact compliance with the short-term mine production schedule. In these cases, the mine production schedule has to be updated, modifying the amount of mineral extracted from the drawpoints and

Tectonic coal refers to the coal with varying degrees of brittle fracture or ductile deformation under the action of one or multi-period tectonic stresses, showing the characteristics of low mechanical strength, weak cohesion and large deformation. Therefore, drilling in tectonic coal is easy to cause the aperture shrinkage or closure due to the poor anti-deformation capability. Enlarging the initial

The water adsorption into pore spaces in brittle rocks affects wave velocity and transmitted amplitude of elastic waves. Experimental and theoretical studies have been performed to characterize moisture-induced elastodynamic variations due to macroporous effects; however, little attention has been paid to the manner in which wetting of nanopores affects elastic wave transmission. In this work, we extend

Anticipating the progressive damage and strength of an anisotropic and interbedded rock mass is challenging due to the overwhelming variables which need to be considered. Therefore, the strength and progressive damage of each rock material is not a realistic model which can be used to define the deformation of the interbedded anisotropic rock mass. In this research, weathered (sandstone-shale-sandstone)

In deep hard rock mines, the drilling and blasting method is mainly used for mining, which results in a complex environment of high static stress and frequent dynamic disturbance in some underground engineering surrounding rocks for a long time. In addition, a large number of underground engineering are in the geological tectonic zone with poor stability, which often triggers rock disasters when stress

Shale anisotropy can lead to deviated patterns of hydraulic fractures in multi-stage hydraulic fracturing (MSHF) operations, significantly hindering hydrocarbon production. Such deviation usually occurs in formations where the induced fractures interfere with natural bedding planes or where the stress shadow is created. In this work, the elastic behavior of a transversely isotropic shale rock during

Fracture injection/shut-in tests are commonly used to measure the state of stress in the subsurface. Injection creates a hydraulic fracture (or in some cases, opens a preexisting fracture), and then the pressure after shut-in is monitored to identify fracture closure. Different interpretation procedures have been proposed for estimating closure, and the procedures sometimes yield significantly different

Microseismic, acoustic emission, and electromagnetic radiation (MS, AE, and EMR) are promising methods for the monitoring and early warning of rock bursts. In the underground mining process, personnel activities and electromechanical equipment produce MS, AE, and EMR interference signals that affect the accuracy of MS, AE, and EMR monitoring. This study is aimed at overcoming the difficulties in identifying

Under the thermodynamics framework, a thermo-hydro-mechanical coupling model was established by a multi-scale homogenization technique for fractured rock mass containing both small-scale arbitrarily-distributed microcracks and large-scale grouped-directionally-distributed fractures. The proposed model simultaneously considers the deformation evolution and permeability and thermal conductivity variations

Investigation of the seepage characteristics and the corresponding repairing effects of slurry on fractured rock mass is of great significance to grouting theory and operation parameters designing. Several chemical grouting tests under different temperatures and grouted pressures were conducted and the seepage processes were monitored by the LF-NMR (low field nuclear magnetic resonance) technique.

In this study, laboratory pull tests of rock bolts were conducted to verify and update existing stress transfer models. The rock bolt samples in the study had different bond lengths that were fully encapsulated in cementitious grout with different water-cement ratios. The test results show that the existing models do not correctly describe the shear stress distribution on the bond length in some loading

Brazilian disc (BD) testing is a typical method for measuring the indirect tensile strength of rock materials. Both experimental and theoretical studies involving BD testing of anisotropic rocks typically focus on the influence of the 2D bedding effect, where a specimen is parallel to the bedding planes, whereas the influence of the 3D bedding effect combining both the orientation and loading angle