Conventional borehole pressure relief can meet the requirements for preventing rock bursts, but it can also easily destroy the roadway, resulting in system support failure. Taking coal-like samples with boreholes as the research object, the pressure relief effects of the same-diameter boreholes and variable-diameter boreholes are compared and analyzed by a uniaxial compression test. The joint pressure relief mechanism of the variable-diameter drilling hole is discussed. The experimental results show that the stress–strain curve of variable-diameter drilling sample occurred the phenomenon of pre-peak stress drop and post-peak stress plateau, which indicates that the variable-diameter drilling hole can enhance the plastic characteristics of coal-like samples. The borehole size dramatically influences the variation of various pressure relief indexes. The evolution law of AE counting the pre-peak and post-peak of borehole samples verified the abovementioned law. Variable-diameter drilling can enhance the plasticity of samples, weaken the brittleness and reduce the impact tendency. Under the maximum size of the variable-diameter drilling hole and the same-diameter drilling hole is same, the pressure relief effect is more significant. The results obtained in this paper can provide a new theoretical basis and technical guidance for borehole pressure relief and roadway support.

In the western mining region, weakly cemented rock layers above the coal seams often lead to frequent catastrophic accidents during mining due to their instability. To address this, this paper analyzes the movement characteristics of surrounding rock in the recovery roadway and the effectiveness of from nearby large coal pillar roadways. A mechanical model for the failure of weakly cemented roadways was established, and numerical simulations were used to verify the feasibility of leaving small coal pillars along soft, thick coal seams. Additionally, existing measurements were used to evaluate the impact of leaving small coal pillars on the deformation of the surrounding rock in the recovery roadway. The results show that after changing the coal pillar retention to 5 m in the 130,205 working face of the Yangchangwan mining area, the roadway is in a low-stress zone, with minimal surrounding rock deformation, meeting safety requirements for production.

The instability of hard and brittle rock often leads to disastrous consequences in underground engineering. Under various surrounding rock pressure conditions, in situ stress induces corresponding deformation and damage to the floor post-mining. Therefore, it is crucial to examine the effects of mining under different confining pressures on rock disturbance, damage characteristics, and their distribution. Consequently, triaxial loading experiments under varying intermediate principal stress conditions were conducted on red sandstone specimens, using an acoustic emission monitoring system to track energy changes during rock damage and failure. This approach aids in studying crack generation, propagation, and fracture damage evolution. The results indicate that rock deformation results in axial compression and dilatancy, aligned with the direction of minimum and intermediate principal stresses. Ductility in rock failure becomes more pronounced with increased stress, primarily manifesting as shear failure. Internal cracks in the specimen lead to stress concentration and marked plastic deformation under compression, yet do not result in macroscopic surface cracks. The fracture angle θ of specimens post-failure generally exceeds 45° and varies with stress changes; at consistent burial depths, the angle of the sandstone failure surface increases with intermediate principal stress. This paper preliminarily establishes the informational linkage between rock failure and energy release, analyzing the rock samples over time and space. This research offers insights for analyzing and mitigating sudden rock instability.

The Shendong mining area, a pivotal coal production base in China, faces considerable challenges due to extensive mining activities. The significant development of overlying rock fractures and the widespread occurrence of surface cracks present a major challenge to mining safety and ecological preservation in China and other mining nations. This study focuses on the Panel 12,401 fully mechanized longwall face at Shangwan Coal Mine to systematically investigate overburden movement and the evolution of surface fractures. By combining UDEC discrete element modeling with a computational framework that links subsurface strata subsidence and surface settlement, this research examines the spatial and mechanical properties of fracture propagation. Experimental results show that surface fractures continue to develop as the working face advances, with their horizontal apertures gradually decreasing and eventually closing after the face passes. Both the maximum surface subsidence and the maximum fracture aperture exhibit a strong positive correlation with mining height. In contrast, increased mining depth leads to reductions in maximum surface subsidence, the subsidence factor, and the size of surface fracture apertures. These findings provide a theoretical basis for reducing mining-induced damage and promoting ecological restoration in mining areas.

The instability of jointed rock masses has been a persistent concern in China’s underground geotechnical engineering, particularly regarding rock mass instability triggered by structural activation, such as faulting. This form of instability constitutes a significant type of dynamic geological hazard in the field of geotechnical engineering. Research on the mechanism of jointed rock mass instability typically concentrates on various characteristics associated with structural activation but frequently neglects the interplay between coalescence instability within the jointed zones and the intact zones, as well as the development and evolution of abrupt water channels. To delve into the coalescence instability characteristics between jointed and intact zones, this study conducted uniaxial compression tests on macro-scale pre-fabricated jointed sandstone. The research results show that the failure process of the specimen consists of a strong deviation linear stage, a sub-critical stage, and an unstable stage. The main failure process occurs during the sub-critical stage.

Based on the engineering background of Daliuta mining area, the fracture distribution and water movement within the weakly cemented overlay strata are studied through liquid-solid coupling physical simulation and COMSOL numerical simulation test. 3D fracture network of overburden strata in mining is plotted based on the result of the physical simulation test. The results showed that the ‘fractured zone’ of the weakly cemented overburden strata in the western area develops more evidently than that in the eastern area ---- wide-opened fractures form at both ends of the working area and this leads to a wide distribution of fractures in the overlying strata.After the initial caving of the roof, height of the penetrating fractures increases rapidly and the separated strata space becomes the main channel for water flow. Under the action of water flow and rock strata movement, mining-induced fractures in overlying rock display cyclic change of expansion, penetration and closure. When the working face is fully mined, the penetrating fractures in the overlying strata and mining-induced fractures up in the working face become the main passages for water flow. The experimental result provides a reference for underground reservoirs layout and maintenance and water-conserved mining in western China.