Bulletin of Engineering Geology and the Environment最新文献

This study experimentally explores the interaction between an anti-dip rock slope and anchor system under unloading conditions. The slope-anchor system, created by inserting anchor bolts into the slope, displays a complex deformation and failure mechanism when subjected to unloading. The anchoring and deformation characteristics of this system are crucial for assessing slope stability and optimizing anchorage. Using the right slope at the Huangdeng Hydropower Station in China as a model, a scale model was constructed to investigate the deformation characteristics, stress distribution, and anchor force in an anti-dip rock slope-anchor system under unloading. The unloading effect was simulated through excavation during the test. The results indicate that both horizontal and vertical stress, as well as stress at shallow depth near the excavation site, decrease sharply upon excavation, while displacement increases rapidly, displaying a step-like pattern consistent with the excavation process. The anchor forces increase during excavation due to the rebound and deformation of the slope. The excavation influences the slope through the unloading effect, causing stress to decrease near the excavation part, while the effect of anchorage acts as a counterbalance against stress changes. Finally, a method for calculating the safety factor for the anchored slope is proposed. The safety factors derived from both experimental and on-site monitoring data exhibit similar trends. This enhanced understanding of the slope-anchor system under unloading conditions can inform more effective strategies for slope stabilization and anchorage optimization.

On December 18, 2023, an Ms 6.2 earthquake struck Jishishan, Bao’an, Dongxiang, and Salar Nationality Autonomous County, Linxia Hui Autonomous Prefecture, Gansu Province, China. This moderate-to-strong earthquake triggered more severe co-seismic landslides than expected, including the catastrophic Zhongchuan Town mudflow, which resulted in the loss of > 20 lives. By conducting comprehensive field surveys immediately after the earthquake, we present a detailed field panorama of the earthquake-triggered landslides and provide a field-based understanding of delineating the spatial distribution patterns and failure mechanisms of the landslides. The majority of the co-seismic landslides are small-to-medium scale shallow ones and concentrated in the loess area in Zhongchuan, Guanting towns of Qinghai Province and Dahejia, Shiyuan, Liugou towns in Gansu Province. Loess falls are the most common co-seismic landslide type and are usually distributed on steep cut-slopes of roads and loess terraces where human activities are intense. The second-most common loess slides tend to occur on valley slopes covered by thick loose loess. Landslides in the bedrock area are less frequent, and the majority are complex geo-disasters involving rock falls and debris avalanches that originated in the upper part of the slopes and tend to cluster at the northern end of Jishishan Mountain. Generally, the distribution and occurrence mechanism of the co-seismic landslides are closely related to lithology, seismic response, terrain, hydrogeology, and human activities in the areas where they originated. Measures need to be taken on the irrigation method and the discontinuities and suspended loose debris to avoid further post-seismic failures.

Microbially induced calcite precipitation (MICP) has emerged as a promising technology for soil solidification and remediation in geotechnical engineering. This review provides a comprehensive overview of recent advancements in MICP treatment, focusing on its performance, mechanisms, applications and challenges. Furthermore, the review discusses the enhancement of soil strength, stiffness and impermeability achieved through MICP treatment, along with its effectiveness in mitigating erosion, cracking and other forms of degradation. In addition, the integration of fibre materials with MICP treatment to enhance soil reinforcement and repair capabilities is explored. The synergistic effects of fibre reinforcement on soil tensile strength, dynamic strength and resistance to liquefaction are discussed, along with optimal fibre types and contents. In addition, the review addresses limitations and challenges associated with MICP treatment, such as susceptibility to acid-rain erosion and long-term degradation under cyclic environmental conditions. Areas for further research and optimisation to maximise the effectiveness and durability of MICP treatment are identified. This review provides valuable insights for researchers and practitioners in the field of geotechnical engineering.

To address the frequent appearance of dynamic disasters during the mining of near-vertical coal seams (NVCS), this study takes the Wudong Coal Mine as the research object and employs methods including theoretical analysis, numerical simulation, and engineering verification. It investigates the mechanism of dynamic disasters induced by the prying deformation of rock pillar, analyzes the stress and energy evolution patterns within the rock pillar, and optimizes the pressure relief blasting scheme. The results indicate that the prying-induced extrusion of interlayer rock pillar serves as the primary source of dynamic loading. A stress concentration zone, measuring 54 m in height and 22 m in width from the B2 roadway, was identified, with stress levels exceeding 21 MPa. This zone is concentrated within 20 m before and after the working face as it advances. Energy accumulation within the rock pillar primarily occurs in the goaf left by the previous mining stage, aligning with the prying extrusion location identified in the theoretical analysis. Based on these findings, ANSYS numerical simulation software was used to optimize blasting parameters, including the blasting method, borehole diameter, and borehole layout. The resulting scheme consists of three deep holes (reverse initiation) and two shallow holes (forward initiation). Field application demonstrates that this optimized blasting scheme effectively reduces high-energy and high-pulse mining microseismic events, achieving a notable pressure relief effect. These findings offer a significant reference point for the management of dynamic disasters in similar mining environments.

A stability analysis of tunnel roof in unsaturated soils subjected to steady infiltration is carried out based on the upper bound limit analysis. By incorporating the apparent cohesion induced by matric suction, a modified Mohr-Coulomb (MC) strength criterion with tension cut-off (TC) is employed to establish a failure mechanism for deeply buried rectangular tunnel roofs under steady infiltration. The expressions of stability number and critical supporting pressure are derived from the energy balance equations to evaluate the stability of tunnel roof. The upper-bound optimal solutions for the stability measures are calculated through optimization algorithms. This study examines the effects of various stratigraphic strength parameters, unsaturated steady infiltrations, and hysteresis effects on tunnel roof stability, and developed potential tunnel roof collapse profiles under varying conditions. Additionally, stability charts for the required supporting pressure of rectangular tunnel roofs are calculated and plotted. This work provides a theoretical basis for the stability assessment of tunnel roofs under unsaturated steady infiltration.

To get a better insight into the creep behavior of water-softening rocks, the creep behavior of minerals, mainly including quartz and chlorite, in red shale before and after water soaking was investigated by using the nanoindentation creep test. The power-law, logarithmic, and exponent functions were compared and comparison results reveal that a sequence of exponential function performs better. The one-dashpot Kelvin model, Burgers model, and two-dashpot Kelvin model were also compared and the two-dashpot Kelvin model depicts the nanoindentation creep data best. Experimental results show that the red shale is composited by the hard inclusions and the clay matrix. Water-rock interaction has no influence on the quartz while the hardness and elastic modulus of chlorite decrease significantly after water soaking for 24 h. The creep parameters, including the creep modulus and viscosity, were calculated for the chlorite before and after water soaking. The creep modulus decreases 29.75–38.24% and the viscosity decreases 13.90-97.28%, respectively. Based on the calculated the strain rate sensitivity, m, the chlorite creep is mainly dominated by dislocation but the quartz creep is dominated by both the dislocation and diffusion. After water soaking, the creep dislocation become more dominant since the strain rate sensitivity shows a decreasing trend. The findings of the present study are of great significance for the control of roadway creep deformation after excavating and exposing to wetting air.

Acid rain erosion and wet-dry cycles significantly impact the rock mass stability. This study aimed to elucidate the impact of acidic wet-dry cycles on both macroscopic and microscopic attributes of red glutenite through implementing water absorption assays, uniaxial compressive testing, and cold field emission scanning electron microscopy (CFE-SEM) examinations on specimens exposed to acidic wet-dry cycles. The results revealed that water absorption, uniaxial compressive strength (UCS), and elastic modulus decrease with increasing wet-dry cycles and decreasing solution pH. The acidic wet-dry cycles lead to the continuous loss of interstitial materials between mineral particles, the continuous development and interconnection of cracks and pores, and the deterioration of the overall structural integrity. A clear negative correlation was observed between UCS and microscopic porosity, and this relationship can be successfully simulated by a newly developed UCS empirical correlation model. Based on damage mechanics theory, an improved semi-empirical constitutive model was established by introducing a compaction coefficient. This model accurately simulates the deformation and failure behavior of red glutenite under acidic wet-dry cycles and load conditions, with model parameters possessing reasonable physical significance.

The sliding system of a slope is a nonlinear mechanical system, in which slip surface wear and changes in system energy constitute a feedback process. To investigate the relationship between feedback characteristics and sliding stability during slope slip, the sliding friction tests were conducted on the sandstone specimens. The results revealed that the friction coefficient exhibits nonlinear variation duing the sliding process. A sliding model of sandstone along the slip surface was established to analyze the sliding behavior of the specimens. During sliding, the shearing of surface asperities is accompanied by a decrease in the friction coefficient, which continues to decline with increasing displacement. Energy dissipation occurs and there is also energy replenishment during the sliding. Within a period, the system’s energy sometimes large and sometimes small, exhibiting a cyclic process of dissipation and replenishment, resembling a tension-relaxation movement in the sliding system. The Van der Pol equation was employed to analyze the system’s dynamic characteristics. During sliding, the system continuously alternates between negative and positive feedback states, leading to a periodic energy pattern characterized by attenuation-growth-attenuation cycles. In addition, a feedback loop for the sliding friction process of the sandstone was established, and criteria for the occurrence of positive feedback is proposed: as the sliding velocity increases, the system’s energy decreases, indicating a positive feedback state. At this time, the system continuously releases energy, the sliding velocity is faster and faster, and the system is unstable.The feedback characteristics study can provide important support for the analysis of the evolution process of landslide disaster.

The gradual deterioration of slope rock masses could lead the slope prone to fail under mining-induced disturbances, which poses significant threats to personnel and equipment safety. Accurate prediction of slope failure severity levels constitutes a critical foundation for effective disaster prevention and mitigation. This work implemented the microseismic monitoring technology to establish a slope failure information database, construct an early warning model, and conduct predictive research on slope failure severity levels. This study presents a three-level classification method for slope failure. The number of microseismic events, microseismic energy, seismic moment, cumulative apparent volume, rainfall, and aggregation index were selected as early warning indicators via correlation analysis. These early warning indicators build an early warning index system for slope failure severity levels. This study introduces an attention mechanism and an improved gating mechanism to establish a hybrid convolutional long short-term memory (LSTM) model for slope early warning. The model enhances feature channels relevant to the current task, increasing the importance of early warning indicator features by 50%. By integrating the input gate, forget gate, and output gate structures into an update gate and reset gate, the internal architecture of the model is streamlined, improving its computational efficiency by 15%. The proposed hybrid model achieves an accuracy of 80.9% in predicting slope failure severity levels, representing improvements of 5.9% and 11.7% over conventional convolutional and LSTM models, respectively. This study provides an efficient and accurate technique for predicting slope failure severity levels, offering significant implications for slope safety research in engineering applications.

On July 19, 2024, a recurrent landslide-debris flow disaster chain was induced by extreme rainfall in Mao’ergou, Qinling Mountains, Shaanxi Province, China, resulting in catastrophic damage to agricultural land, residential infrastructure, and transportation networks. This event exemplifies high-vegetation-coverage (HVC) and cycle-recurring patterns, which are characterized by concealed source material and complex activation mechanisms under extreme rainfall. Through integrated UAV-based remote sensing, multi-source geospatial data fusion, and field geomorphological mapping, this study deciphers the spatiotemporal characteristics and recurrence mechanisms of vegetation-masked geological hazard chains governed by geomorphology-source material-hydrology (GM-SM-H) coupling. Some key findings reveal: (1) The steep topography provided a topographic basis for energy conversion; the last debris flow accumulation and the source material generated by new landslide were synergistically activated under extreme rainfall; (2) A GM-SM-H-driven avalanche-like feedback loop initiated an avalanche-like feedback loop of material accumulation and energy amplification via “scraping (slope failure)-erosion (channel confinement)-entrainment (alluvial fan saturation)” mechanisms. This study provides a representative case study for the risk assessment, prevention, and control of geological disaster chains in the Qinling Mountains and similar (HVC) mountain regions worldwide.