Energy-absorbing anchor bolts are widely used in geotechnical engineering, but there is no effective numerical simulation approach for evaluating them at the engineering application level. According to typical laboratory test results, the energy absorption criterion (F ≥ Fy) and breakage criterion (δ ≥ δf) are defined. The constant resistance energy absorption mechanical model and the increasing resistance

Stope backfilling is increasingly used in underground mines. Barricades are necessary to retain slurried backfill poured in mine stopes. In Canada, waste rock barricades (WRB) have been becoming more and more popular to retain paste backfill in stopes. A few solutions have been developed to size the WRB. Among them, a solution developed by Yang and coworkers in 2017 is particularly relevant. However

Water jet drilling (WJD) is an effective technique for drilling micro-holes in the subsurface for reservoir stimulation. This study aims to investigate numerically the failure mechanism of rock during WJD and to assess the WJD performance before drilling. A 3D fluid-solid coupling model is developed for simulating WJD by coupling a mechanical solver based on the combined finite-discrete element method

With the significant development of coal mining, complex coal reservoir environments with a high gas content, high stress, and low permeability increase the difficulty in efficient and large-scale extraction of gas. To further study the mechanism of coal–rock fracturing using a high-voltage electric pulse (HVEP) and to determine the influence of the HVEP on the permeability enhancement, a multi-field

Direct shear tests on samples containing similar triangular asperities have been carried out under constant normal stiffness (CNS) conditions, and observations demonstrated that there exists local lift-off of shallower asperities across the interface, resulting in a redistribution of local stresses and further impacting the global shear behavior. This study further modifies the existing theoretical

This study aimed to investigate the acoustic emission (AE) behavior of rock salt under combined creep and fatigue. The loading path was in a stress-controlled mode and contained a constant stress load with different durations, followed by cyclic loading. The AE counts, peak frequency, amplitude, b-value, and RA (rise time/amplitude)-AF (average frequency) distribution were systematically analyzed.

Earthquake can cause significant rock fracturing in either the short or long terms. A comprehensive analysis of the fracturing mechanism is critical for assessing the risks of potential slope failures, landslides and rock avalanches in seismic prone areas. This study employed 2D discrete element method (DEM) to investigate the fracturing of an intact rock slope of 600 m in base length and 300 m in

Soil-rock-mixture (SRM), consisting of high-strength rock blocks and low-strength soil, is widely distributed in nature. In traditional methods such as limit equilibrium methods, this geomaterial was simplified as a uniform medium without considering the influence of rocks due to its heterogeneity and complex physical and mechanical properties. A coupling method that bridges discontinuous deformation

Coupled static-dynamic tests were carried out on notched semi-circular bend (NSCB) granitic specimens using a modified split Hopkinson pressure bar (SHPB) device, to investigate the effects of axial pre-force and loading rate on dynamic fracture behavior of rocks. Digital image correlation (DIC) method was adopted to obtain the deformation field and fracturing process. The results indicate that the

Near-wellbore rock fracture is a key subject in subsurface energy extraction. Casing perforation completion is perhaps the most used type of well design mainly in comparison to the open hole completion. However, the effects of the combined casing-cementing-rock structure on pressure transmission in fracturing the rock have not been sufficiently addressed, but is key to understanding some important

Tar-rich coal was directly combusted during power generation, resulting in a huge waste of precious oil resources and a large amount of carbon emissions. The idea of intelligent unmanned mining machine (IUMM) for in-situ fluidised mining and conversion of tar-rich coal was proposed to solve the problems of traditional mining and utilisation methods, realise efficient utilisation of tar-rich coal, and

Three-dimensional (3D) printing is an emerging technology capable of producing exact replica specimens in rock mechanics. In this work, the sand 3D printing was explored to model the influence of cyclic freezing and thawing (F-T) for high-porosity weak rocks, which is one of the serious threats to rock stability in a cold region. The evolution of pore structure in the printed specimen during the F-T

Identifying shale geological temperatures is important for understanding the thermal maturity, thermal evolutionary history, and hydrocarbon generation stages of shale formations, and enables efficient shale gas development. This paper investigates the thermal Kaiser effect of shales under different warming rates by studying the thermoacoustic emission (TAE) characteristics of shales in the Lower Palaeozoic

It is critical to rigorously determine the mechanical properties of granitic rocks to effectively analyze and manage subsurface engineering activities, such as geothermal energy exploitation and nuclear waste disposal. However, the required deep drilling and sampling for macroscale rock mechanics experiments (macro-RME) are challenging and expensive. In this study, we developed a novel accurate grain-based

The predisposition of a slope to generate rockfalls is related to the intensity of rock mass jointing and the geometric arrangement of discontinuities intersecting the rock face. With the increasing use of terrestrial laser scanner (TLS) in rock slope surveying, methods have been proposed to semi-automatically extract the spatial properties of outcropping discontinuities from high-resolution topographic

The effective stress law and the permeability play a notable role in dealing with the gas-solid coupling problem of porous media. The key parameter to quantify the influence of pore pressure to effective stress is the effective stress coefficient αij. However, current relevant researches are mainly focused on the pore elastic flow characteristics in the elastic stage or hydrostatic pressure under conventional

Previous studies have revealed that hydraulic fracturing behavior in crystalline rock (e.g., granite) is highly dependent on mineral content, grain size, and heterogeneity and is therefore quite different from the behavior observed in sedimentary rock (e.g., sandstone). We investigated hydraulic fracture paths generated via cyclic and monotonic injection in Pocheon granite, Gonghe granite, and gray

Pre-investigation of geological conditions beyond the excavation face is crucial for assessment of safety and design in underground construction. This study developed a boring data monitoring system equipped for a multi-setting smart-investigation of the ground and pre-large hole boring (MSP) machine that typically drills a horizontal distance of 50 m to reduce blast-induced vibration. The monitoring

Abstract not available

As underground mining operations move deeper and the stresses encountered become more adverse, mine pillars are experiencing increased stress-induced damage and rock mass bulking. This has led to significant challenges in designing effective support systems, leading to costly mine development, production delays and support maintenance and rehabilitation requirements. Efforts to assess rock mass bulking

The 3D reconstruction of rock joint surfaces is crucial for quantifying rock joints. Through the uniform discretization of 2D and 3D rock joints, it was determined that both the climbing angles along the shear direction and the projection lengths of the consecutive ascending/descending segments follow normal distributions. This statistical distribution of climbing angles and projection lengths provides

An elastoplastic damage constitutive model is constructed in this work to describe the macroscopic mechanical behaviors of geomaterials with a “porous matrix - inclusion” microstructure. In order to consider the influences of microstructure on its nonlinear behavior, such as the porosity, volume fraction of inclusions and the properties of the solid phase, the macroscopic yield criterion derived in

Most rocks exhibit time-dependent deformation and failure. Two main mechanisms are generally considered, the progressive growth of cracks and viscoelastic and/or viscoplastic deformation. In this study, cracking process is described by a viscous phase-field method which is coupled with a viscoplastic model. The evolution of crack field is controlled by both elastic and viscoplastic tensile volumetric

A series of cyclic compression tests of marble spheres and scanning electron microscopy (SEM) imaging measurements were performed in this work. The cyclic compression tests of marble spheres reveal three different fracture types: Hertzian cracks, oblique fractures and multi-meridian fractures. The displacement of marble spheres with Hertzian cracks or oblique fractures in cyclic compression tests can

The scaling laws describing the spatial arrangement of fractures along six deep boreholes penetrating the crystalline rocks in the Rhine Graben were derived using a correlation analysis. Five of the wells, two to 5 km depth, were located at the Soultz geothermal site and one well to 5 km depth was located at Basel, some 150 km from Soultz. Five datasets were derived from borehole imaging logs, whilst

The deep coal reservoir is in a high in-situ stress regime, and the drop in pore pressure during the coalbed methane extraction can induce significant slippage effect and effective stress change. Both of them play a competitive role in permeability evolution. In our research, coal seepage experiments under variable bulk stress and pore pressure paths are performed to investigate the slippage effect

Understanding the stress distribution, deformation and fracture behavior around a circular hole or inclusion is critical for the stability assessment of rock structures such as tunnels and backfilled openings. In this study, the analytical solutions of stress and displacement distribution around a circular inclusion of different elastic properties were first derived based on the theory of elasticity

Petrophysical properties of cylindrical core specimens from three boreholes from the International Continental Scientific Drilling Program, the DSeis project, measured at ambient pressure and room temperature conditions in various laboratories are presented and compared with downhole petrophysical data (sonic and density). The measured properties are from sixty-six rock specimens constituting metasediments

Distributed acoustic sensing (DAS) is being applied in an increasing number of geoscientific fields. We present herein preliminary results of applying DAS to monitor microseismicity in underground mines. We installed 275 m of fiber optic cable approximately 1500 m below the surface in an operational mine and recorded mine seismicity for two weeks during November of 2018. The first approximately 50 m

Wellbore instability is an important consideration during both drilling and production of hydrocarbon reservoirs. The optimal well trajectory must be determined during the design phase to avoid wellbore shear failures. This study makes two fundamental contributions towards improving contemporary wellbore shear models. For the first time, the analytical wellbore shear models are formulated implicitly

The main objective in this study is to experimentally investigate how two types of shales different in swelling characteristic and organic carbon content behave in terms of the mechanical and infiltration properties when being subjected to changing osmosis with varying brine salinity under in-situ stress conditions. This research also aims to determine the swelling tendency of thePierre shale and replicate

Abstract not available

A comprehensive analysis of crack initiation and propagation in coal is critical for understanding its mechanical behavior and its impact on permeability. The finite element-based digital volume correlation (DVC) of time-resolved X-ray tomography images under cleat-parallel uniaxial compression provides 3D incremental strain fields to understand the evolution and propagation of cracks. In this study

This study proposes a novel method to determine the five elastic constants from a single-orientation core of a transversely isotropic rock using strip loading and strain inversion. The proposed method can be performed under two test conditions: 1) strip load test and strain inversion (single strip load method) and 2) strip load test combined with Brazilian test and strain inversion (strip load and

The implementation of multi-crack recognition requires a theoretical basis from single-crack failure results. This study investigates the spatial distribution pattern of microcracks in single-crack-damaged coal specimens subjected to uniaxial compression. The distribution mechanism of the induced microcracks is analysed in terms of macrocracks and stress states. Gaussian and Weibull distributions are

In underground mining, rock mass stress is commonly modeled as a continuum. However, in block cave mining discrete modelling should be used to properly represent the stress over the extraction level in the broken column where there are high rock columns of large rock fragments. Unfortunately, we lack methods that use discrete modelling of stress in the broken column at block caving scale. In this work

A three-dimensional CFD-DEM simulation method was developed to investigate the influence of different reservoir fluids on sand production. The fluid properties and reservoirs were prescribed and modelled after the conditions in the Kenkiyak and Uzen oil fields in Kazakhstan. A cylindrical sandstone sample was modelled using the Discrete Element Method in three stages of the pluviation, diagenesis,

In cold mountainous regions, the freeze-thaw cycling often leads to rock weathering, which might trigger spalling, significant landslides and rockfalls. In this work, we used combined experimental, theoretical and numerical approaches to investigate the mechanisms of frost cracking as a result of coupled effects of freeze-thaw cycling, confining stress and the interaction of multiple cracks. The experimental

The DECOVALEX Project is an international research collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. DECOVALEX stands for “DEvelopment of COupled Models and VALidation against EXperiments”. The creation of this international initiative, now running for almost 30 years, was motivated by the recognition that

The mechanical properties of rock masses are significantly affected by the deformated behaviors of discontinuities, such as joints and faults. Rock masses in nature are also often subjected to dynamic disturbances, including explosive and seismic loads. Therefore, it is crucial to understand the deformed response of rock joints under dynamic loads. In this study, a series of dynamic compression expriments

The problems of cost, environmental protection and efficiency of hard rock fragmentation in petroleum exploration, drilling and other projects need to be solved urgently. Electro-pulse-boring (EPB) technology has attracted attention due to its advantages of low rock breaking energy consumption, low wear and low time cost. However, there is still no more accurate description model for EPB and rock fragmentation

This paper investigates the effects of the gradient distribution of microdefects on wave propagation through a rock mass. A piecewise three-characteristic lines method is proposed that can consider the gradient distribution of microdefects. A rock mass with a microdefect gradient distribution was explored and compared to wave propagation through a rock mass with a uniform distribution of microdefects

Strain burst occurs within highly stressed hard rocks in underground excavations. A prerequisite for strain bursting is that excess energy exists to eject material after rock failure. Both the bursting rock and the surrounding rock mass will contribute to the excess energy. However, the proportion of the energy contributed from each is currently not well understood. This issue will be quantitatively

In this study, we investigated the failure process and evolution mechanisms in circular tunnels under a complex stress path of deep in-situ stress + excavation unloading + stress adjustment using a simulation test based on loading first and then drilling (LFTD) mode. This test was performed on cubic sandstone specimens using a true-triaxial testing system combined with a self-developed drilling unloading

High-porosity granular rocks are moisture-sensitive solids, in that their strength and deformability are modulated by the relative humidity of their environment. Here, a novel continuum breakage–damage framework is developed to characterize and simulate the inelasticity of cemented granular materials subjected to changes of relative humidity. A microstructural model is proposed to describe the evolution

In this work we use the peridynamics theory of solid mechanics to simulate fracture in an annular rock domain subject to an in-situ stress and create surrogate models that predict the area of the resulting cracks. Peridynamics is a non-local formulation of continuum mechanics that naturally accommodates material discontinuities. Furthermore, unlike other fracture modeling techniques there is no need

This study reports on the mixed-mode behavior of desiccation cracks in a clayey rock front gallery. As most digital image correlation (DIC) algorithms have access to the full-field measurements of the displacements and strains, the improvements in DIC now allow the automatic detection of the jumps in the displacements induced by the opening and sliding of desiccation cracks without imposed initial

This study systematically investigates the effect of deviatoric loading paths on diffuse and localized deformation developing during the mechanical loading of a high porosity (20%) Vosges sandstone (Eastern France). Laboratory scale experiments are performed using a high pressure true triaxial apparatus, designed to provide access to full-field surface kinematics at high spatial and temporal resolutions

To investigate the anisotropy of coal swelling, this study proposes an effective stress model for saturated, adsorptive fractured porous media by considering gas adsorption induced surface stress change on solid-fluid interface. The effective stress model can be used to capture the anisotropic swelling of coal combining anisotropic mechanical properties and to link with the anisotropic permeability

The shearing characteristics of rock joints govern the mechanical performance of discontinuous rock masses. The present study investigated the normal compression and shear behavior of rock joints through cyclic compression tests and direct shear tests. The irreversible relationship between the normal stress and the normal closure was confirmed by cyclic compression tests on rock joints. An elastoplastic

Mechanical response with a snapback (class-II behavior) is one of the basic features of brittle rocks. This technical Note presents analytical studies on the critical condition which separates the class-I and class-II rock behaviors. Formulations under conventional triaxial compression are performed by making direct use of the closed-form solutions of the damage-friction coupling constitutive equations

Ground surface uplift was detected during longwall mining in the Lazy Mine, a hard coal mine in the Czech part of the Upper Silesian Coal Basin, Czech Republic. The greatest uplift was 218 mm, based on surface point levelling by comparing surface points with heights of non-mined areas. This uplift occurred during subcritical mining at an average depth of 740 m below the surface. The mined coal seam

To investigate the static mechanical properties and failure characteristics of damaged rocks after impact under realistic in-situ stress, dynamic triaxial compression tests with different strain rates and confining pressures were conducted on diorite by a modified split Hopkinson pressure bar. The damage factor was calculated according to the change of the longitudinal wave velocity of rocks before

This study reveals the important role of hydromechanical responses of large hydraulic fractures in the cause and mechanisms of induced seismicity associated with the Mw 5.5 earthquake at the Pohang geothermal site, South Korea. Fractures intersecting two stimulation wells, PX-1 and PX-2, were identified through a comprehensive analysis of various data produced from drilling and hydraulic stimulations

The salts contained in water can gradually accumulate in pore networks of rocks under wetting-drying cycles, which could cause rock deterioration. The salt-induced damage under this cyclic process can result in dynamically evolving mechanical and hydraulic properties of the rock, which is relevant to many rock-related engineering activities and geological hazards. In this study, the structure damage

To investigate frictional properties of the rupture surface of the carbonate Jiweishan rock avalanche, we conducted high-velocity-friction tests on the limestone and shale samples at different shear rates. The samples showed shear- and rate-strengthening of friction at low shear rates, but transformed to shear- and rate-weakening of friction at large shear rates. The critical shear rate was deduced

Numerical modelling is widely used to estimate seismic potential in mines. Several numerical methods, along with different interpretation techniques, allow estimating the seismic potential at different stages of a mine or tunnel construction. However, none of the existing methods considers the magnitude of seismic events as a distribution of values, rather all methods focus on obtaining a single value