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Stratified rock masses comprise various rocks with different thicknesses, lithologies, and compositions. They exhibit unique cracking morphology and failure modes when subjected to external loads. Understanding and mastering the fracture morphology and failure laws of stratified rock masses under three-dimensional mechanical conditions is crucial for researching disasters in underground engineering geology. This paper presents a three-dimensional double-layer rock mass model established using the numerical calculation method based on mesoscopic statistical damage mechanics. The model simulates the cracking mode of the rock surface under biaxial tensile conditions. The simulation results are quantified using PCAS software. Crack indexes, such as the number of cracked blocks, average cracked block area, and surface crack rate, are used to evaluate the degree of influence of different factors on the cracking of the rock surface layer. The results indicate that the degree of surface crack development varies linearly with the degree of homogeneity (m). Additionally, the layer thickness ratio (η) is positively correlated with the average fragmentation area, and the two are logarithmic. Regardless of the model scale, the average circumference of each block is approximately equal to the model side length. The model exhibits the highest degree of crack development when the loads in the x and y directions are equal. Moreover, the degree of crack development in the model is also influenced by the loading per step, and the two are proportional. [ABSTRACT FROM AUTHOR]

To address the critical issue of slope stability in jointed rock masses with complex and rough structural planes, a rough joint network model using the Fourier transform was proposed and applied to the Shilu open pit mine. The on-site structural plane survey results were combined with MATLAB and PFC2D to establish numerical models for slope stability analysis considering both linear-jointed and rough-jointed rock slopes. By comparing the slip body and fracture distribution, it was found that the rough-jointed slope was stabler than the linear-jointed slope. In addition, the fracture patterns and slip displacement were significantly influenced by the inclination and undulation of the bedding planes. Slip failure patterns occurred when the angle of inclination was set at 60°. The joints played a crucial role in inducing the shear strength of slope rock masses, and the slide area was mainly observed in the shallow slope surface for inclination angles of 0° and 45°, and in the middle deep area for 60° and 90°. These results demonstrated the importance of considering rough non-persistent fractures when developing a new numerical model for slope failure modes. [ABSTRACT FROM AUTHOR]

To address the critical issue of slope stability in jointed rock masses with complex and rough structural planes, a rough joint network model using the Fourier transform was proposed and applied to the Shilu open pit mine. The on-site structural plane survey results were combined with MATLAB and PFC2D to establish numerical models for slope stability analysis considering both linear-jointed and rough-jointed rock slopes. By comparing the slip body and fracture distribution, it was found that the rough-jointed slope was stabler than the linear-jointed slope. In addition, the fracture patterns and slip displacement were significantly influenced by the inclination and undulation of the bedding planes. Slip failure patterns occurred when the angle of inclination was set at 60°. The joints played a crucial role in inducing the shear strength of slope rock masses, and the slide area was mainly observed in the shallow slope surface for inclination angles of 0° and 45°, and in the middle deep area for 60° and 90°. These results demonstrated the importance of considering rough non-persistent fractures when developing a new numerical model for slope failure modes.

Rock fragmentation is a critical process for mineral extraction and for mitigating overstressed rock in geotechnical applications. In this study, 3D-printed concrete was used to simulate the stratified rock mass, and experimental and numerical methods were employed to investigate crack propagation under static expansive loadings in transversely isotropic rocks. Two types of cracks were observed in the experiments: P-type (a crack propagates primarily along the weak layer) and T-type (a crack propagates across the weak layers) cracks. The findings revealed that the orientation of layers significantly influenced the initiation and propagation of cracks, with P-type cracks commonly observed in simpler P-P mode fragmentations and more complex P-P-T modes emerging under higher expansive loadings. P-T-T modes were characterized by the simultaneous presence of the T-type crack after an initial P-type crack. The AE energy levels in the P-P-T and P-T-T modes were much higher than those in the P-P mode. 2D-DDA models were further built to understand the effects of the loading scales, layer angles, and locations of weak layers on the cracking sequences. The results provided detailed insights into stress evolutions and the impact of expansive loadings on crack initiation and propagation. • P-P, P-P-T and P-T-T mode fragmentations were identified for stratified rock under SCDAs charging. • P-P fragmentation was the major failure mode in stratified rock mass. • T-type crack occurred if the centroid of the hole offset the weak layer and was continuously loaded. [ABSTRACT FROM AUTHOR]

• High-precision tunnel model is fabricated through 3D printing technology and cast-in-place process. • Failure mechanisms of tunnels in horizontally stratified rock masses are revealed. • Targeted engineering prevention and control recommendations are proposed. A number of typical cases in China show that for tunnels in stratified rock masses, the tunnel structure and surrounding rock are often exposed to damage, which affects the safety of tunnel construction and operation. In this study, the failure and deformation mechanism of tunnels, in the horizontally stratified rock formation are investigated by a large-scale model test. The stratified rock mass and elaborated tunnel structure in the model test were carefully designed and produced to be more in line with the actual site conditions. The test results indicate that the failure of horizontally stratified rock mass under high horizontal ground stresses is mainly concentrated in the tunnel bottom and vault. The gradual failure process started with the interlayer separation, followed by the bending failure of rock layers, and finally resulted in the shear-slip failure of the rock mass. After obvious interlayer separation and apparent rock layer bending cracks, the rock mass formed a dominant failure surface which allows shear-slipping to occur along the dominant failure surface under the compression of horizontal ground stress. The stratified rock layers show a bending failure towards the tunnel centre with the shear–slip line inclined approximately 60° to 80° to the horizontal. After the stratified rock mass starts to damage, the increase of the lateral pressure coefficient will intensify the floor heave behaviour of the tunnel. The tunnel structure failures in the test mainly include crush failure at the vault, longitudinal penetration cracks at the central gutter, and tension penetration cracks at the sidewalls. In the stratified rock stratum with high ground stress, attention should be paid to preventing the tunnel floor heave, strengthening the inverted arch if necessary, and paying attention to the crack detection of the tunnel structure during the operation. [ABSTRACT FROM AUTHOR]

• Initial unloading level has obvious effect on the mechanical and failure characteristics of stratified rock mass. • Variations of area fraction along the specimen height are first used to represent the micro cracks distribution characteristics. • With the increasing initial unloading level, the energy index value and energy dissipation rate at the peak stress increase approximately linearly. In order to study the strength, micro crack distribution and energy evolution characteristics of stratified rock mass under unloading confining pressure conditions, triaxial compression tests and triaxial unloading confining pressure tests at different initial unloading levels were carried out. The experimental results indicated that the triaxial unloading confining pressure plus axial stress is a stress path between the stress state of uniaxial compression and triaxial compression. With the increasing initial unloading level, the specimen is closer to the stress state of triaxial compression, the peak stress, peak axial strain, peak circumferential strain and peak volume strain increase linearly, Poisson's ratio decreases linearly, failure type of specimens shows 4 typical characteristics. When the bedding plane inclination is 45°, 3D reconstruction and quantitative characterization of micro cracks of stratified rock mass specimens are conducted based on CT scanning results. Variations of area fraction along the specimen height show 3 typical characteristics. The stratified rock mass mainly stores and dissipates energy before the peak stress, and mainly releases and dissipates energy after the peak stress under different conditions. With the increasing initial unloading level, the input energy, elastic energy, dissipative energy and energy dissipation rate at the peak stress increase approximately linearly. [ABSTRACT FROM AUTHOR]

The article presents a novel yielding mechanism, especially designed for the rock bolt support. Mechanical rock bolts with an expansion head and equipped with one, two, four and six dome bearing plates were tested in the laboratory conditions. Furthermore, in the Phase2D numerical program, five room and pillar widths were modeled. The main aim of numerical modeling was to determine the maximal range of the rock damage area and the total displacements in the expanded room. The models were made for a room and pillar method with a roof sag for copper ore deposits in the Legnica-Głogów Copper District in Poland. Additionally, in the article a load model of the rock bolt support as a result of a geomechanical seismic event is presented. Based on the results of laboratory tests (load–displacement characteristics), the strain energy of the bolt support equipped with the yielding device in the form of dome bearing plates was determined and compared with the impact energy caused by predicted falling rock layers. Based on the laboratory tests, numerical modeling and mathematical dynamic model of rock bolt support, the dependence of the drop height and the corresponding impact energy for the expanded room was determined.

The complex engineering characteristics of stratified rock masses make the comprehensive analysis of TBM tunneling more complex and difficult. In this study, an advanced modeling method based on the coupled finite difference method (FDM) and discrete element method (DEM) was proposed for the simulation of open TBM tunneling in stratified rock masses. The modeling and analysis process of the FDM-DEM numerical model was presented with the DLS Tunnel as the research background. Numerical results show that the displacement values and characteristics of the rock mass are consistent with the deformation of the surrounding rocks obtained from in situ monitoring. Severe shear and tensile fractures occur progressively in both rock blocks and bedding planes during TBM tunneling. The extent of the loosening area in the rock mass also continues to grow. The numerical model reproduces the progressive failure process of the stratified rock mass through the analysis of contact fracture events and the evolution of contact forces. The simulation of the interaction between the rock mass and the shield is accomplished by FDM-DEM coupling methods under the large-strain mode. This study presents an effective tool for the comprehensive analysis of open TBM tunneling in stratified rock masses. [ABSTRACT FROM AUTHOR]

• The deterioration of uniaxial compressive strength in the stratified rock mass is investigated. • Effects of bedding inclination angles and original materials strength on the failure of stratified rock mass are investigated. • This study investigates the failure process of the stratified rock mass. Stratified rock mass usually exists in sedimentary formation, composed of at least two lithological units with different mechanical properties, which may cause numerous disasters to engineering protection and construction. Investigation of mechanical properties and failure modes of stratified rock mass helps solve these problems. This study investigated the uniaxial compressive strength of stratified rock mass with different strength ratios of the original materials. The experimental results reveal the relationship between the strength difference of lithological units, the percentage of soft rock and uniaxial compressive strength in the soft and hard rocks alternate-layered rock mass. In addition, the failure modes were investigated by using simulated specimens under compressive loads. The experimental results indicate that the dip angles of the bedding plane and the mechanical properties of original materials in stratified rock can directly affect crack initiation and propagation behavior and eventually result in different failure modes. The crack distribution characteristics were also investigated in this study to provide more references to further decisions on the cracking problem. [ABSTRACT FROM AUTHOR]

In order to analyze fracture mechanism of floor heave in entry and to enhance the stability of strata under floor, thus further guarantee the normal transportation of coal mine, this paper made a research on the evolution law of stress slip-line field, ultimate load and speed, there also investigated the floor heave mechanism and countermeasures of fold-like entry in bedding stratum, which exists in Datun mining area. The results show that two main factors influence floor stress greatly, namely, width of the entry and frictional angle of strata, it also demonstrates that supporting strength and anchoring parameters can be designed scientifically with the help of deductive anti-heave mechanical model, whose controlling effects is impressively. Especially as to deep buried entry under the circumstance of bedding stratum, longtime stability can be obtained with the supporting strength more than 0.4 MPa, which is demonstrated effectively based on the two years monitoring period of Kongzhuang Mine, and floor heave less than 10 mm, either. [ABSTRACT FROM AUTHOR]

A stratified rock mass model was founded by FLAC3D. The failure mode and anisotropic characteristic of strength for stratified rock mass were analyzed. The analysis results show that the numerical simulation can visually reflect the failure modes of rock samples under different inclination angles β of structural plane. The stiffness of rock sample before peak strength changes in the compressive procedure. With the increase of β, the compressive strength σ c of rock sample decreases firstly and then increases; when β is in the range of 20°–30° and 80°–90°, σ c has the largest sensitivity to β; while β falls in the range of 30°–70°, σ c varies little. When ϕ j < β<90° (β j is friction angle of structure plane), the results obtained from numerical simulation and theoretical analysis are in almost the same values; while β⩽ ϕ j or β=90°, they are in great different values. The results obtained from theoretical analysis are obvious larger than those from numerical simulation; and the results from numerical simulation can reflect the difference of compressive strength of rock samples for the two situations of β⩾ ϕ j and β=90°, which is in more accordance with the real situation. [ABSTRACT FROM AUTHOR]

The paper addresses the important issue of allowing for the inelastic properties of rock in stability problems for a stratified rock mass. A three-dimensional nonlinear problem statement is used. An exact method to study the surface instability of a regularly layered semi-infinite medium is developed. New numerical results are obtained [ABSTRACT FROM AUTHOR]

The article presents a novel yielding mechanism, especially designed for the rock bolt support. Mechanical rock bolts with an expansion head and equipped with one, two, four and six dome bearing plates were tested in the laboratory conditions. Furthermore, in the Phase2D numerical program, five room and pillar widths were modeled. The main aim of numerical modeling was to determine the maximal range of the rock damage area and the total displacements in the expanded room. The models were made for a room and pillar method with a roof sag for copper ore deposits in the Legnica-Głogów Copper District in Poland. Additionally, in the article a load model of the rock bolt support as a result of a geomechanical seismic event is presented. Based on the results of laboratory tests (load–displacement characteristics), the strain energy of the bolt support equipped with the yielding device in the form of dome bearing plates was determined and compared with the impact energy caused by predicted falling rock layers. Based on the laboratory tests, numerical modeling and mathematical dynamic model of rock bolt support, the dependence of the drop height and the corresponding impact energy for the expanded room was determined. [ABSTRACT FROM AUTHOR]