Abstract This work presents a hybrid discrete fracture-dual porosity model of compressible fluid flow, adsorption and geomechanics during CO2 sequestration in coal seams. An application of the model considers the influence of hydraulic fractures on CO2 transport and the stress field of the coal. The low initial permeability of coal is compounded by the injectivity loss associated with adsorption-induced

Abstract It is of great significance to obtain the high precise structural surface properties of rock mass during the process of deep geotechnical engineering investigation by in-situ instrumentation, especially for preventing disasters and reducing damages. To obtain more detailed features of the structural surface in the image obtained by digital panoramic borehole imaging technique, this paper describes

Abstract An experimental study of 3-D crack growth from initial cracks of different shapes and inclinations in biaxial compression with different biaxial load ratios (\( \sigma_{x} /\sigma_{y} \)) is presented. Unlike 3-D crack growth in uniaxial compression, which is characterised by the presence of intrinsic limits on 3-D growth of wing cracks associated with wing wrapping, in biaxial compression

Abstract In the present study, the effect of thermal treatment on the physical, mechanical and fracturing behavior of Gondwana shale samples from India was investigated. Acoustic Emission signals were used to identify the changes brought in by temperature variations on the crack damage zones and failure attributes in shale. The results suggested that mechanical parameters such as uniaxial compressive

Abstract Nano- and microparticles are expected to have several functionalities, and the ability to control size and shape is an advantage of using nano-/microparticles. This study investigated a possibility that the sizes of nano-/microparticle can be used to extract new information on structures in a fractured medium. Flow experiments were conducted to observe the particle transport in a micromodel

Abstract This work aims to examine the stress redistribution with evolving seismicity rates using a passive seismic tomographic tool. We compiled a total of 26,000 events from two underground mines and partitioned them into multiple clusters in a temporal sequence, each of which contains 1000 events. To image stress redistribution associated with seismicity rates, we then run the tomographic studies

Abstract Heterogeneous rock contains numerous pre-existing three-dimensional (3D) cracks, which control its mechanical and fracturing properties. Considerable effort has been devoted to studying the volumetric fracturing behaviour of rock under static loading conditions. Although rock masses are often subject to dynamic impacts such as earthquakes and blasting, the mechanical and volumetric fracturing

Abstract A novel 3D grain-based model (3D-GBM) based on Voronoi tessellation technology is proposed and implemented into a three-dimensional particle flow code (PFC3D) to investigate the micromechanical properties of salt rock at the grain scale. Parameter calibration is performed for numerical test configurations with various microparameters matched with the macroresponses observed in laboratory experiments

Abstract This paper presents the results of laboratory tests conducted on a series of mini-cylinder specimens to measure the uniaxial compressive strength of sub-bituminous coal, which is sparsely recorded in the public domain. The measurements were made on mini-cylinder specimens (non-standard) sized from 9.3 to 22.6 mm in diameter, sourced from the Surat–Clarence–Moreton Basin in Australia, an important

Abstract In laboratory tests, in rock, elastic wave conversion occurs when shear cracks initiate. In the experiments, the samples are continuously probed with seismic waves during loading that caused shear crack initiation and growth. The initiation of shear cracks is not detected with either transmitted P- or S-waves across the crack. However, shear (S) waves, propagated at normal or oblique incidence

Abstract Laboratory experiments are performed on Laizhou granite samples after heating and rapid water-cooling treatment to investigate the thermal effects on the physical and mechanical properties and fracture initiation of granite during the utilization of hot dry rock. Experimental results show that P-wave velocity and tensile strength monotonously decrease because of the generation of thermally

Abstract Theoretical explanation of rock cutting mechanism with a conical pick is a very difficult task due to inherent complexities in the cutting action. Furthermore, previous studies evidently showed that theoretical models have difficulties on estimating the cutting force accurately. The empiricism seems as the only option for proposing a general force estimation equation with considering the strength

Abstract A thermally induced wedging–ratcheting mechanism for slope stability is investigated using a large-scale physical model and using a three-dimensional version of the numerical Distinct Element Method (3DEC). The studied mechanism consists of a discrete block that is separated from the rock mass by a tension crack filled with a wedge block or rock fragments. Irreversible block sliding is assumed

Abstract Clayey rocks have a complex microstructure with multiple characteristic lengths. Deformation under mechanical loading generally induces damage by microcracking, which essentially concerns the scale of mineral inclusions embedded in the clay matrix. The modelling of these materials is considered within the framework of a double scale approach, by numerical homogenisation, of the squared finite

Abstract Delayed rockburst occurs after the stress adjustment of surrounding rocks with discontinuous microseismicity, which is difficult to predict accurately. To predict and prevent the occurrence of the delayed rockbursts, study on time behavior of the surrounding rock failure and the mechanism behind the delayed rockbursts is necessary. In this article, based on the rockburst data from Jinping

Abstract The thermo-hydro-mechanical behavior of the host rock is essential while designing an underground radioactive waste disposal repository, and in particular, while considering the long-term safety of the facility. In 2000, the French National Radioactive Waste Management Agency (Andra) started constructing an underground research laboratory located in the Meuse Haute Marne to carry out a research

Abstract The dynamic permeability evolution of a fracture is a key scientific problem for fluid flows in rock masses within engineering systems. Understanding the dynamic permeability evolution and its mechanism is conducive to design and operation engineering. The dynamic permeability evolution of a rough granite fracture was revealed by laboratory experiments and numerical models. The permeability

Abstract To investigate the tensile behavior of rock bedding planes, a series of direct tensile tests were conducted on cylindrical limestone and sandstone specimens with a distinct bedding plane perpendicular to the axial direction. Different tensile strain rates of the bedding plane areas within the magnitude range from 10−6 to 10−2 s−1 were considered. The results indicate that the limestone fracture

Abstract To understand the influence of shear on the hydraulic properties of rock fractures, shear-flow tests were carried out on rock fractures with different surface roughnesses. Each rough-walled fracture was replicated in four specimens, which were sheared at different displacements under normal stresses that varied from 0.5 to 2.0 MPa. At each shear displacement, a series of hydraulic tests with

Abstract Lined rock cavern at shallow depth is identified as a promising alternative and cost-effective solution for air storage of large-scale compressed air energy storage (CAES) plant. To better understand the thermodynamic process of the compressed air in the underground cavern and the response of the surrounding rock during air charging and discharging phases, a small-scale pilot cavern with concrete

Abstract The preparation of standardized soft rock specimens to perform unconfined compressive strength (UCS) tests is typically difficult, expensive and time-consuming. Needle penetration test (NPT) was originally developed in Japan as an alternative for the indirect estimation of UCS of soft rocks. The needle penetrometer is a simple, portable and non-destructive testing device that measures applied

Abstract This study presents the experimental results of the mechanical characterization of artificial rock joints constructed by 3D-printing (3DP). The mechanical behavior of rock masses is controlled by the presence of joints. Understanding the mechanical behavior of rock joints is essential to predict their influence on a rock mass. The application of innovative 3DP technology in rock mechanics

The article Analytical Solutions for Tunnels of Elliptical Cross-Section in Rheological Rock Accounting for Sequential Excavation, written by H. N. Wang, S. Utili, M. J. Jiang, P. He, was originally published.

Abstract This paper presents a case study on the impact of jointed rock mass deformation on liner stability for an inclined excavation at the Bulianta Coal Mine. The tunnel was excavated by a single shield tunnel boring machine (TBM), with part of the excavation passing through a heavily jointed rock mass at great depth. Serious local instabilities occurred at one side of the liner due to highly asymmetric

Abstract A transversely isotropic rock, slate, was utilized to investigate the size effect and anisotropy on its deformation, tensile strength, and failure mechanism. A series of Brazilian tests were conducted on slate samples of six different sizes from 25 to 100 mm in diameter at seven different loading-foliation angles from 0° to 90°. The results indicate that the Young’s modulus in the plane of

Abstract There is intrinsic difficulty in the investigation of the largest volume of rockfalls that is expected in an area, which lies in the small number of large events, in registrable times. The maximum credible rockfall size has been associated with the properties of the rock mass discontinuities, as they delimit detachable rock blocks, and in particular with the penetration of those discontinuities

Abstract The deformation of mountains induced by reservoirs around high arch dams may influence the safety of those arch dams, but the underlying mechanisms of this phenomenon have not yet been elucidated. The abutment movements of the Jinping-I and Xiluodu arch dams during reservoir impoundment are analyzed systematically in this paper, and the analysis reveals that impoundment led to basin irreversible

Abstract For rock fractures, the degradations in the strength of contacting asperities and the surface frictional resistance are responsible for the water-induced weakening in the shear strength. To quantitatively examine their independent roles, direct shear tests on sawtooth fracture samples of granite and sandstone under three moisture conditions: dry, surface wet and saturated, were conducted subject

Abstract At present, shale gas plays a significant role in hydrocarbon reservoirs. Hydraulic fracturing is generally employed in the exploration and exploitation of shale gas. Economic and efficient hydraulic fracturing, known as volume fracturing, is largely associated with formation characteristics, including anisotropy and brittleness in rocks. Further research on the mechanical properties of rocks

Abstract Applying accurate normal load to a specimen in direct shear tests under constant normal stiffness (CNS) is of importance for the quality of the resulting data, which in turn influences the conclusions. However, deficiencies in the test system give rise to a normal stiffness, here designated as system normal stiffness, which results in deviations between the intended and actual applied normal

Abstract Due to the complexity of the interaction between hydraulic fractures (HFs) and natural fractures (NFs), several different interaction behaviours (arrest/cross/offset) may occur, according to hydraulic fracturing experiments. The existing analytical criteria cannot accurately describe this interaction process and predict the interaction behaviours by adopting several simple assumptions. An

Abstract Unintentional variations of fluid pressure within a hydraulic fracture will disturb the surrounding stress state, affect the stability of fracture propagation and complicate the fracture intersections during the process of hydraulic fracturing. However, little attention has been paid to the effect of nonuniform fluid pressure inside the hydraulic fracture. This paper presents a semianalytical

Abstract Almost all reservoir rocks contain natural fractures. The presence of such discontinuities affects reservoir stimulation to a certain degree. The interaction between the natural and hydraulic fractures determines the overall fracture trajectory and the stimulated reservoir volume. In contrast to conventional hydraulic fracturing, natural fractures do not propagate in a tensile-dominated regime

Abstract Two types of experiments were conducted under different boundary conditions to characterize the anisotropic deformation and directional permeability of the coal sample. Gas sorption-induced strains in the three principal directions were studied to examine the anisotropic deformation. The results show that the coal sample can be treated as isotropic in those planes parallel to the bedding direction

In 2001, researchers from the National Institute for Occupational Safety and Health (NIOSH) installed instruments at the Turquoise Ridge Mine in cooperation with Placer Dome, Inc. to monitor the geomechanical behavior and stability of a cemented rockfill (CRF) sill and the surrounding host rock during test mining of a large undercut span beneath backfill. Six parallel, adjacent drifts were mined and

Underhand cut-and-fill mining has allowed for the safe extraction of ore in many mines operating in weak rock or highly stressed, rockburst-prone ground conditions. However, the design of safe backfill undercuts is typically based on historical experience at mine operations and on the strength requirements derived from analytical beam equations. In situ measurements in backfill are not commonplace

Ground control research in underground coal mines has been ongoing for over 50 years. One of the most problematic issues in underground coal mines is roof failures associated with weak shale. This paper will present a historical narrative on the research the National Institute for Occupational Safety and Health has conducted in relation to rock mechanics and shale. This paper begins by first discussing