The anisotropic mechanical and acoustic emission characteristics of oil shale from room temperature to 600 °C were studied using a real-time high-temperature uniaxial rock testing machine independently developed by the Taiyuan University of Technology and an acoustic emission test system. The results indicate that the elastic modulus and compressive strength of the oil shale perpendicular to bedding

In high-temperature rock engineering projects, rocks are subjected to external loads. Studying the cracking behavior of thermally damaged rock under uniaxial loading is of great significance to engineering. In the present study, real-time computed tomography (CT) scanning was performed on thermally damaged granite subjected to compression loading to observe the evolution of spatial three-dimensional

The Draupne shale is a rock formation functioning as overburden for gas reservoirs in the Norwegian Sea and potentially as caprock for future CO2 storage locations as well. In this paper, the Draupne shale was exposed to several fluids: CO2 gas, supercritical CO2, CO2 gas dissolved in brine, supercritical CO2 dissolved in brine, as well as brine and dry air. The motivation for the exposure tests was

Disc cutter wear is a crucial problem that influences the working efficiency and security of hard rock tunnel-boring machines (TBMs). When tunneling and rock breaking with TBM, the cutters at the forefront of the cutter head directly contact the tunnel face, where wear is serious due to a harsh working environment. In this study, the Cerchar abrasivity index (CAI) of various rock samples was obtained

Replacing worn disc cutters in a tunnel boring machine (TBM) operation is a time-consuming and expensive process. This article presents the study of disc cutter wear rate during the excavation of 36 km Naqadeh water conveyance tunnel with a diameter of 6.325 m. The construction of this tunnel in northwest Iran has been recently completed. The geological setting of the tunnel consists of variable lithology

The in situ state of rock mass stresses is a key design parameter, e.g., for deep engineered geothermal systems. However, knowledge of the stress state at great depths is sparse mostly because of the lack of possible in situ tests in deep boreholes. Among different options, core-based in situ stress estimation may provide valuable stress information though core-based techniques have not yet become

The importance of discontinuity geomechanical properties is increasing as the use of numerical models with explicit or discrete rock mass structure becomes the state of practice. Joint normal stiffness and joint shear stiffness are two parameters that characterize the deformation behaviour of discontinuities. This paper presents practical guidelines to correct direct shear testing data for machine

Under high temperature and stress reservoir conditions, proppant embedment induced by the time-dependent creep behavior of shale rocks has posed great challenges to the long-term maintenance of fracture conductivity in unconventional reservoirs. In this study, a numerical workflow combining a 3D continuum–discrete mechanical coupling approach with the lattice Boltzmann (LB) method is developed to simulate

In the context of salt cavern applications, this experimental study is dedicated to the characterization of fluid transfer and poromechanical properties of salt rock under isotropic and/or deviatoric stresses. Triaxial test was used to investigate permeability variation with deviatoric stress and time, and simultaneously to get damaged sample. Uniaxial test was also performed as it is more likely to

Rock breaking technique plays an important role in rock excavation engineering, such as mining, tunnel construction and hydropower engineering. Pneumatic fracturing with carbon dioxide (CO2) ice powder is potentially a safe and efficient rock breaking method, which is one of the most pertinent research topics in rock breaking. A site test of pneumatic rock breaking with CO2 ice powder was carried out

The stability analysis of rock blocks on man-made excavation faces (e.g. tunnel, cavern, and slope) subject to seismic loads is an important issue in the field of rock engineering. This paper proposes a generalized block theory (GBT) by combining a pseudo-static method and the traditional block theory to evaluate the stability of blocky rock masses during earthquake activities. In our analysis, the

Wave velocity as a nondestructive test is widely used in various fields such as mining, civil, rock mechanics and rock engineering, and dynamic elastic properties of rocks are also determined by wave velocity. Rock mass contains discontinuities with different orientation angles, numbers of sets and frequencies and the impacts of such discontinuity properties on the wave velocity have not yet been systematically

Ultra-long-term storage of spent nuclear fuel and other waste products is most likely to be accomplished through the construction and safe closure of deep geological repositories (DGRs). Around the world, numerous countries are planning, designing and in some cases, building such repositories in sound rock between 400 and 1000 m below surface. In Ontario, Canada, both crystalline (granite, gneiss,

In this work, we propose a modified phase-field model for simulating the evolution of mixed mode fractures and compressive driven fractures in porous artificial rocks. For the purpose of validation, the behaviour of artificial rock samples, with either a single or double saw cuts, under uniaxial plane strain compression has been numerically simulated. The simulated results are compared to experimental

High temperatures can cause deterioration of the physical–mechanical properties of rocks. In this study, the triaxial cyclic loading and unloading of rock specimens under different temperature conditions were investigated to reveal stress–strain curves, strength and deformation characteristics, failure forms, and peak stress dropping of the rock specimens at high temperatures. The deformation of treated

As a common lithology material of tunnel surrounding rock, rock mass in fault fracture zones is often wetted by groundwater to produce extensive wetting-induced deformation, which threatens the long-term stability of underground engineering. To investigate the wetting-induced deformation behavior of such surrounding rock mass and to explore effective maintenance and control techniques, the strength

The cumulative damage effects of surrounding rock under single full-face blasting and multiple full-face blasting of a large cross-section tunnel are comparatively studied in this paper. The damage processes of the single and multiple full-face blasting of the tunnel are simulated by the established rock damage model embedded into the LS-DYNA computer code through its user subroutines and a cumulative

The sliding of rock blocks along rock discontinuities is caused by accumulated deformation and can result in disasters such as rock bursts and earthquakes. Creep along rock discontinuities leads to the accumulation of sliding deformation and random instability over time. The initial stress and deformation are important factors that strongly influence creep behavior. To investigate the influence of

Surface measurements are used extensively in many industries and research disciplines to characterize a material’s mechanical properties and strength without the need for traditional, time consuming, and expensive laboratory tests, or for large volumes of sample material. This paper briefly reviews indentation methodologies for index and physical properties measurements and then focuses on the implementation

Numerous rockfall incidents involving infrastructure damage and loss of life have been reported along roads in mountainous terrain. Previous studies have used quantitative risk assessment approaches to identify the level of rockfall risk. However, appropriate quantitative indicators that are able to describe time-varying risk have not yet been developed. This study aims to develop a rockfall risk mitigation

Despite major improvements over the past several decades in computer methods for analyzing and synthesizing exploration and site investigation geological data for engineering purposes, which should have decreased project risk, unexpected failures and construction problems still occur. Often, this unexpectedness can be tied back to inadequate structural geological understanding of actual site-specific

It has been found that the physical and mechanical properties of rockfill materials deteriorate when subjected to wetting–drying cycles. Previous studies have mainly focused on the variations of mechanical properties of rockfill materials with wetting–drying cycles. However, the effects of wetting–drying cycles on the breakage characteristics of rock grains still remain unclear. In this study, we perform

Equilibrium thermodynamics has been of fundamental importance to many branches of engineering including cyclical mechanical applications. However, in geomechanics and geological applications it has not yet reached a consensus in the community. Reason for the failure of establishing thermodynamic laws as a ground principle is the far from equilibrium nature of geomechanical problems which prevent the

The cracked chevron notched Brazilian disc method (CCNBD) recommended by the International Society for Rock Mechanics is a major method for measuring the rock fracture toughness. In the rock fracture mechanics, the micro-crack evolution behavior during Mode I fracture is of great theoretical significance. To fully understand the micro-crack evolution mechanism and fracture process zone evolution information

The use of asymmetrical disc tools for the mining of hard and very hard rocks is a promising direction for developing mechanical mining methods. A significant obstacle in developing mining methods with the use of asymmetric disc tools is the lack of adequate computational methods. A deep understanding of rock–tool interaction can develop industrial applications of asymmetric disc tools significantly

Understanding coal rib geomechanics is essential for improving rib stability and eliminating fatality and injury trends due to rib failures. There are presently no standardized rib control practices available in most countries. In light of this observed dearth, this investigation aims to improve understanding of rib failure mechanisms using the distinct element modeling (DEM) technique. DEM is chosen

Time series prediction refers to the learning of existing observed data of a parameter and predicting its future evolution. Based on the application of machine/deep learning methods in the field of engineering geology, it is desirable to predict the time series evolution of microseismic parameters in the process of rockburst development. Our study explores key microseismic indices that help describe

Extension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression

In this work, effective thermal conductivity (λEff) of fractured rock masses was numerically investigated. A two-dimensional Discrete Fracture Network (DFN) model of the fractured rock masses was established based on the statistic results of natural fracture development in a potential area for high level radioactive waste disposal in China. Steady state heat transfer processes in the fractured granite

The slotted cartridge is able to generate strong directional penetration. To study the effect of different structures of slotted cartridges on the propagation characteristics of shock waves and explosive products, the high-speed schlieren photography system and pressure testing system were used to conduct experimental investigations based on five different structures of slotted cartridges. Experimental

The size of a fracture within a rock mass can be obtained using borehole sampling data or exposed surfaces. This paper aims at building a method to estimate the fracture size, without the presupposed size distribution, based on full three-dimensional geometric parameters (shape, orientation and position). In this study, the rock fracture was considered as an elliptical plane, and each set of fractures

Offshore oil reservoirs are mostly loose sandstone. Sand control completion is usually required. However, sand control screens are easily blocked during production, reducing the productivity of oil wells considerably. The optimization of the sand control screen is still a challenge to date because of the lack of insights into the screen plugging process. In this study, a CFD-DEM method was introduced

In the current study, a series of laboratory triaxial loading and unloading experiments were conducted for the purpose of comprehensively understanding the effects on sandstone of loading processes under axial stress conditions and unloading processes under confining pressure conditions. The mechanical properties and crack propagation behaviors of sandstone specimens were analyzed. In addition, a new

Underground rock is often subjected to the coupled action of acid sulfate, chloride ion corrosion, and external dynamic disturbance: the degree of corrosion and dynamic load can significantly affect the pore structure and mechanical behavior of rock. To quantify the microscopic pore structure changes and macro-dynamic behavior characteristics of acidified corroded sandstone, first, a mixed acidic solution

The permeability of shale reservoirs is an important parameter in evaluating the feasibility of shale gas commercial exploitation. The influence of structural anisotropy, bedding planes, and effective stress is of great significance to the permeability of shale reservoirs; thus, a further study on the permeability of shale rock containing bedding planes and fractures is necessary. In this paper, to

In practical rock engineering, Universal Distinct Element Code (UDEC) is one of the most widely used two-dimensional software packages for simulating discontinuum behaviors of rocks and rockmasses. Over the years, this software has been used to study phenomena, such as grain-scale fracturing in laboratory specimens, spalling around tunnels and roadways, shearing and separation along discontinuities

Hot dry rock (HDR) is an important renewable energy resource within the overall energy mix. However, its popularization is restricted by drilling costs due to the high hardness and abrasiveness of the rock. As a type of cryogenic fluid, liquid nitrogen (LN2) could aggravate the damage of high-temperature rocks and provide a novel insight in improving the drilling efficiency of HDR. To investigate the

To solve the problems of severe early wear of the teeth of the roller-cone bit and the low service life of the bit in the highly abrasive hard formation, a biconical-profiled single cone bit structure is proposed. The cone of the drill bit is biconical, and the tip of the cone is larger to increase the tooth density. The front end of the cone is embedded in the center area of the bottom hole to ensure

We re-investigate the laboratory acoustic emission (AE) source location from a hydraulic fracturing test. This test produces temporally well-separated AE releases exhibiting first the reverse Omori–Utsu law (ROU-AEs), and following later the normal Omori–Utsu law (NOU-AEs) behaviors. One fault was cut in the hydraulic fracturing specimen. The spatial permeability changes along the direction of minimum

Experimental measurements during laboratory tests on salt specimens are important for the design of underground facilities in salt formations. These measurements, especially of the volumetric strain, can be influenced not only by the errors inherent to the experimental work, but also by the material heterogeneity. The natural variability due to the presence of impurities can lead to a non-negligible

The method of backfill in underground mining is important for ground control as well as material recycling and energy efficiency. Even though extensive testing and field studies of backfill have been conducted, less is known about the detailed damage and fracturing that occurs directly at the rock/backfill interface. In this paper, cylindrical specimens containing an inner diameter of backfill and

In this study, the smoothed particle hydrodynamics method was modified to the two-phase-improved kernel of smoothed particle hydrodynamics (2P-IKSPH). By mapping the water pressure of the water base particles to the solid base particles, the hydraulic fracturing processes of rock masses were realised in a set of unified equations, which could reduce the amount of calculation and improve calculation

Seismic waves can be an effective probe to retrieve fracture properties particularly when measurements are coupled with forward and inverse modelling. These seismic models then need an appropriate representation of the fracturing. The fractures can be modelled either explicitly, considering zero thickness frictional slip surfaces, or by considering an effective medium which incorporates the effect

During the construction of tunnels in the central and western regions of China, diorite is frequently affected by vibration, blasting and water which will lead to the questions of the quality and operational safety of project. However, there are few studies on the dynamic characteristics of diorite under the action of dry–wet cycles. Therefore, this paper selected the gray–green altered diorite from

Brittleness is an important property of rocks in the context of engineering applications, as it often determines how severe the practical consequences of rock yield will be. Many authors have proposed various brittleness indices intended to allow for relative categorization of brittleness, but many are relatively simplified and/or only applicable for certain categories of rock. This study provides

Diagnostic fracture injection tests (DFITs) have been performed extensively in unconventional reservoirs to derive reservoir properties such as pressure, permeability, and closure stress. Since most horizontal wells in unconventional reservoirs are drilled in the direction of the minimum horizontal stress, prevailing studies typically presume that hydraulic fractures are oriented transverse to the

Fractures provide preferential flow paths and establish the internal “plumbing” of the rock mass. Fracture surface roughness and the matedness between surfaces combine to delineate the fracture geometric aperture. New and published measurements show the inherent relation between roughness wavelength and amplitude. In fact, data cluster along a power trend consistent with fractal topography. Synthetic

Data integrity and reliability during seismic event detection are the main factors limiting the effectiveness of seismic monitoring systems in underground mines. As it is impossible for current seismic monitoring systems to record all mining-induced seismic events, the incomplete seismic dataset may cause significant bias during data analyses and interpretation processes. Evaluation of seismic data

The fragmentation of coal produces abundant coal gases and is presumed to be the defining characteristic of coal and gas outbursts. Knowing the mechanism of these catastrophic hazards is one of the most important breakthroughs in mining geology. In the outburst process, coal spallation represents a unique failure type and typically leaves behind a spallation area (with a series of fracture textures)

Observations of the mechanical behavior of porous rocks subject to external loading indicate the existence of complex dependencies on the level of confining pressure, fluid pressure and rate of deformation. Due to the heterogeneous nature of porous rocks, their macroscopic response is the result of underlying microscopic processes which can alter the microstructural organization of the grain–pore network

Time-dependent rock deformation affects both natural processes happening on the geological time scale and subsurface engineering operations. We perform a series of multistage triaxial experiments on a set of natural limestone and artificial samples. We study rock response during creep and stress relaxation tests, which are two endmembers of time-dependent rock response. The tests were conducted at

The injection of fluids into a compartmentalized formation induces pore pressure buildup and may result in reactivation of sealing faults. Among other variables, the pore volume compressibility (PVC) can affect the amount of pore pressure change during injection. PVC has been traditionally measured with isotropic loading compressibility tests. However, long and thin reservoirs subjected to depletion

The mechanical properties and permeability of gypsum caprock have a significant influence on the tightness and stability of salt cavern gas storage, a series of tests were carried out to investigate the mechanical properties, permeability and AE characteristics of gypsum under THM coupling in this work. The peak strength of gypsum increases with the increase of confining pressure and the decrease of

Liquid nitrogen (LN2) cooling can induce significant cracking damage in coalbed methane (CBM) reservoirs. To investigate the combined effects of LN2 cooling and bedding angles on the mechanical behaviors of bedded coal, coal specimens with different bedding angles (0°, 30°, 60° and 90°) were cooled. The variations in the surface features and P-wave velocity of the specimens were analyzed. The mechanical

A concomitant effect of a hydraulic fracturing experimenting is frequently fluid permeation into the rock matrix, with the injected fluid permeating through the porous rock matrix (leak-off) rather than contributing to the buildup of borehole pressure, thereby slowing down or impeding the hydro-fracturing process. Different parameters, such as low fluid viscosity, low injection rate and high rock permeability

Hydrofracturing technology has become successful in enhancing the permeability of shale gas reservoirs. However, given the geological complexity in the subsurface, considerable challenges remain in quantitatively analyzing the hydrofracture geometry and understanding the anisotropic fracture process. To investigate, we conducted hydrofracturing tests through a horizontal borehole in shale core samples

The generation of a fracture network in reservoir rocks for fluids to flow via hydraulic fracturing is important in shale oil and gas development, and the intersection between hydraulic and natural fractures is key in bridging natural fractures. In this work, the intersection behaviors between hydraulic and natural fractures and fracture propagation in a three-dimensional (3D) space were investigated

The recovery of unconventional natural gas is a potential solution to the increasing worldwide energy demand and therefore plays a crucial role in the global energy landscape. However, the rapid reduction of production often experienced during the initial recovery phase of unconventional natural gas resources is a major concern. Therefore, an advanced understanding of realistic fracture characteristics

To evaluate the ultimate capacity of the ground reinforced embankments, most of the research have been focused on high levels of impact energy. However, many existing embankments have been impacted by several blocks without collapsing. The residual characteristics and efficiency of post-impact embankments under low-energy impact are researched in this paper. Model tests of two types of embankments

It is valuable to build an empirical model to estimate rock mass deformation modulus which is difficult to be determined by in situ tests. Based on 84 data sets from Yalong River Jinping-I hydropower station, the correlation between some easily measured geotechnical parameters and rock mass deformation modulus is analyzed. A two-parameter estimation model with higher estimation capacity than previous