Bulletin of Engineering Geology and the Environment最新文献

The geometry of the failure surface of anti-dip bedding rock slopes (ABRSs) is often not a regular arc or folded line. Progressive failure with multi-level failure surface is observed in the failure process of ABRSs. This study proposes a stability assessment method for ABRSs that considers the multi-level failure surface to address this challenge. The proposed new approach considers the formation of multi-level failure surfaces within the deformation and failure process of ABRSs. It utilizes an Atomic Orbital Search (AOS) optimization algorithm based on the Tent chaotic mapping strategy to locate the multiple failure surfaces of ABRSs. Centrifuge tests were employed to verify the validity of the proposed method. The research results indicate that the proposed strategy improves the convergence speed of the AOS, in comparison to the standard algorithm, while also avoiding the problem of getting stuck in local optima; the multi-level failure surfaces of the ABRS located by the proposed method are consistent with the results of the centrifuge tests, achieving a high degree of prediction accuracy; the rock mechanics parameters of internal friction angle of joints and tensile strength of the rock layer significantly affect the critical failure surface position of ABRSs.

The blasting excavation of the new tunnel will adversely affect the adjacent existing tunnel structure, to ensure the safe operation of the busy existing tunnel, the study of blasting vibration safety control is critical. In this study, based on the Xiamen New Damaoshan Tunnel No.1 project, the conversion relationship between the input energy of blasting vibration and the elastic strain energy and kinetic energy of concrete mass unit is analyzed according to the principle of conservation of energy. The estimation method of " twice the peak kinetic energy of the peak vibration velocity instead of the maximum elastic strain energy" is proposed, and verified by numerical simulation method. On this basis, the safe control of the vibration velocity of the existing tunnel in this project was derived by combining it with the energy criterion of concrete damage. Secondly, the blasting vibration damping control test is carried out using a test well and on-site monitoring, and the relationship between the blasting distance and the peak vibration velocity and damping efficiency is obtained for the three control techniques of the Single hole blasting, Preset damping holes, and Rope saw cutting, and the results show that the damping effect of the control technique of the Rope saw cutting is the best, and the damping effect of the Preset damping holes is second to the control technique of the damping. Finally, according to the adaptive range of different vibration control techniques for engineering application, through the peak vibration velocity monitoring of the existing tunnel, the peak vibration velocity is less than the safe vibration velocity control value proposed in this study and is in a safe state.

To study the correlation between the mesoscopic damage evolution and macroscopic failure characteristics of anisotropic shale, an in situ high-resolution micro-computed tomography (micro-CT) was used to conduct a uniaxial loading experiment with real-time scanning on Carboniferous shale from the eastern Qaidam Basin. The subvoxel displacement field of each specimen was calculated based on the correlation coefficient interpolation of the image subset with the digital volume correlation method, and the high-precision strain field was obtained to evaluate the deformation localization characteristics of shale specimens with low and high bedding inclination angles during loading. The research results show that the stable cracks expansion is caused by the synergistic effect of tension and shear. However, the unstable cracks expansion in low bedding inclination angle shale is controlled by tension and shear, whereas in high bedding inclination angle shale, it is dominated by tension. The evolution of the axial strain field of the low bedding inclination angle shale confirms the compaction of the bedding defects, strengthening bedding planes and inhibiting the formation of cracks along bedding. Conversely, high bedding inclination angle shale experiences concentrated tensile and shear strains due to damage to original bedding defects, leading to rapid strain increase and localized strain band formation consistent with subsequent splitting failure. The strain localization can predict the development location of cracks before they become macroscopically visible in CT images.

A large and catastrophic landslide occurred at the Xinjing Coal Mine (XCM), China on February 22, 2023, resulting in 59 casualties. It was reported that one of the triggering factors of this landslide was that the actual engineering slope, which was excavated by reduced steps. This paper presents analytical approaches to investigate the effects of steps number and steps width on the stability of stepped rock slopes. The dip angle of sliding surface θ was used to characterize the critical sliding surface (CSS) of rock slopes, and analytical solution of θ was derived with limit equilibrium method (LEM). Discrete element method (DEM) was conducted to verify the accuracy of the proposed approach. The effects of the geomechanical and geometric parameters on XCM Landslide were investigated by parametric analysis. It was found that the driving factors of the XCM Landslide was the design slope steps numbers was reducing from 4 to 3, i.e., the slope was excavated with combined-step. Specifically, with the increase of the number and width of steps, the slope stability gradually improved. This study provides useful guidelines to location of CSS of open pit slopes and scientific design of open pit mine rock slopes with multi-steps.

With the advancement of equipment technology, the mining height of coal mine working faces has been increasing year by year. In thick coal seams with high mining heights, the frequent occurrence of rib spalling in coal faces has become a prominent issue, leading to unclear mechanisms and increased difficulty in controlling rib spalling. This paper employs a comprehensive approach combining theoretical analysis, physical experiments, numerical simulation, and mathematical statistics to investigate the influencing factors of rib spalling in coal faces. An orthogonal experimental model for coal face rib spalling is established, quantifying each influencing factor and ranking their sensitivity. Consequently, control strategies for rib spalling in fully mechanized top coal caving faces of thick coal seams are proposed. These findings provide valuable insights for managing rib spalling in similar conditions with high mining heights and offer guidance for selecting control factors against rib spalling.

Rock slopes with cracks may remain stable under static conditions, but large-scale landslides may occur when subjected to seismic excitations. However, the presence of cracks has been long overlooked in existing studies on the dynamic stability of rock slopes. Attempts are successfully made in the current work to conduct comparative shaking table tests on bedding rock slopes with and without cracks, where the dynamic responses and failure modes of both types of slopes are systematically investigated. The results indicate that the presence of cracks significantly influences the propagation and response of seismic waves in slopes. When the input seismic amplitude exceeds 0.4 g, both types of slopes exhibit nonlinear dynamic response characteristics. The evolution process of slope surface displacement can be categorized into three stages: elastic deformation stage, plastic deformation stage, and failure stage. The damping ratio and natural frequency of both model slopes respectively show gradually increasing and decreasing trends, thereby the relationship between seismic input motion and damage coefficient has been established. The presence of cracks obviously alters the failure mode of the model slope and significantly increases the landslide volume. The bedding rock slope without cracks exhibits a single-stage sliding trend, while the one with cracks presents a multi-stage sliding trend. The findings of this research might facilitate the stability assessment and seismic design of bedding rock slopes. 

Studying the shear rheological properties of clay is crucial for evaluating slope stability and preventing excessive displacement of roadbeds and retaining walls. In this study, a series of direct simple shear tests were conducted by a novel apparatus to investigate the shear rheological behavior of clay in western China. Test results reveal that both the shear strain–time curve and shear stress–strain curve can be well described by power functions, and the power of shear strain–time curve is independent of the shear stress level. Based on this finding, an empirical shear rheological equation under constant shear stress is built. By assuming the shear stress–strain curves as a series of parallel lines in a double logarithmic coordinate axis, shear equivalent timelines are proposed based on Yin Graham's equivalent timeline theory. The shear equivalent time is then introduced into the proposed empirical shear rheological equation, thereby an equivalent timeline shear rheological model considering the effect of consolidation pressure under varying shear stresses is derived. The shear rheological strains predicted by the model are shown to agree well with test data before clay failure.

The mine pressure in deep mining is enormous, which can easily lead to coal bursts. At present, the method of automatically formed roadway (AFR) by roof cutting has been widely used in shallow buried coal mines. However, there is a lack of systemic research about the whole process of forming and reusing AFR in deep coal mines. Therefore, by analyzing the structural characteristics and stress distribution of AFR, the mechanism of pressure relief and energy reduction of AFR was revealed, which reduced the peak stress and energy of the roadways and the reserved coal pillar was cancelled. To verify the effect of pressure relief and energy reduction of AFR, the numerical comparison test of gob-side roadway driving and AFR was carried out. Two quantitative evaluation indexes of reducing rate of stress and energy were established, and the effect of pressure relief and energy reduction of AFR was verified. What’s more, the field results showed that AFR can effectively reduce the stress, micro-seismic energy and deformation of roadway. Compared with the method of gob-side roadway driving, the maximum stress, the maximum micro-seismic energy and the deformation of the roof using AFR decreased by 24.46%, 62.33% and 40.40%, respectively. Furthermore, the construction processes an engineering suggestions d of AFR were put forward. This paper provides an effective guidance of AFR in deep coal mines. 

This study uses discrete element method models to simulate the fragmentation and deposition of landslides with varying volumes on terrains with different slopes and heights. The slope motion process during the numerical simulations of the landslide movement can be divided into three stages based on changes in the kinetic energy. The variations in the kinetic and frictional energies throughout the mass motion are used to establish pertinent parameters to analyze the dynamics of the slider fragmentation characteristics. Building on prior research, the impact of the slope on the mobility and deposit morphology, including the apparent and equivalent friction coefficients and the ratio of the width to length as a deposit morphology model, is examined using motion models. Concurrently, the three experimental variables (the slope gradient, slope height, and sliding block volume) are analyzed and discussed in conjunction with the motion and deposit morphology models. Previous studies indicate that the quantification of landslide fragmentation is only applicable to rock landslides and has limitations. In the numerical simulations, distinct contact models for pre- and post-fragment particles are defined to enumerate the total number of intact particles. Subsequently, a dimensionless parameter is formulated to quantify the degree of slope fragmentation. The relationship of this parameter with the motion and deposition models is subsequently explored. The results show that increased fragmentation reduces the landslide mobility, indicating that fragmentation is an energy-consumptive process that hinders landslide motion. These findings provide insights into the mechanisms of long-runout landslides and contribute to the reproduction of landslide dynamics.

This study explores the mechanical behavior and properties of sand-rubber-gravel (SRG) mixtures under various testing conditions. Through an extensive series of experimental tests—including direct shear, oedometer, saturated and unsaturated triaxial, and cyclic triaxial tests—the effects of rubber and gravel additions on sandy soil are systematically evaluated. The findings reveal that the appropriate content of rubber and gravel is crucial for ensuring the improvement of soil properties. An insufficient addition may not significantly enhance the soil’s properties, while an excessive amount can lead to a deterioration of its mechanical characteristics. With the optimal mixture ratio, test results show significant improvements in shear strength and deformation resistance of the SRG mixtures compared to pure sand. Under saturated and unsaturated conditions, the SRG mixtures demonstrate enhanced bearing capacity. In addition, dynamic response of SRG mixtures to varying cyclic loads are revealed through cyclic triaxial tests. The study confirms the feasibility and effectiveness of using SRG mixtures to improve the mechanical properties of sandy soils, suggesting their potential for diverse geotechnical applications.