Quantitative determination of the critical size of an inclined coal pillar in an old goaf water-affected area is of great significance for water damage prevention and safe mining. The critical size of the inclined waterproof coal pillar is derived by using mechanical analyses, numerical calculations, and field engineering practices to determine the stability of the waterproof coal pillar in the old goaf water-affected area of the 1303 working face of Dananhu No. 1 Mine in the Xinjiang region. Firstly, a force model of the inclined waterproof coal pillar was established to reveal the law that the critical size of the coal pillar increases with the increase in coal seam inclination under the action of asymmetric load. Then, numerical simulation was applied to reveal the dynamic evolution processes of plastic deformation–destabilization of the coal pillar under the influence of mining and single-side water pressure, and the critical size of the coal pillar in the study area was determined to be 19.09 m. Finally, measures such as pumping pressure relief and slurry reinforcement were adopted to reduce the deformation rate of the roadway on the side of the coal pillar, which ensured the stability of the waterproof coal pillar and the safe mining of the working face.

Aiming at the complex issue of dynamic disasters induced by hard rock layers fracture during the mining of gently inclined close distance coal seams, this study employs an integrated approach combining numerical simulation, microseismic monitoring, and mechanical analysis to investigate the fracture evolution process of hard rock layers under the influence of an inverted trapezoidal overburden. A cantilever beam structural model of interlayer rock layers was established, from which the deflection curve and rotation angle equation at the critical fracture state were derived. The elastic energy released upon fracture of the cantilever beam was quantified. Furthermore, by considering the characteristics of the overburden above residual coal pillars, the interplay among the total energy released during interlayer rock fracture, the strength of the cantilever structure, and the inverted trapezoidal overburden load was elucidated. Specifically, a heavier inverted trapezoidal load increases the disaster-induced energy applied to the cantilever structure, a longer cantilever beam accumulates greater elastic energy, and a stiffer beam structure can accumulate more energy. The interaction between these three factors makes it easy to induce strong mining pressure when the hard rock layers break during close distance coal seam mining. Accordingly, combined prevention measures involving water injection softening and blasting roof cutting were proposed to mitigate dynamic hazards and ensure safe mine production.

Performing stability studies of waterproof coal pillars is one of the key measures for preventing mine water disasters. As some areas of the coal pillar were affected by goaf water in the Nanhu Second Mine, the coal pillar and surrounding roadway were somewhat deformed. To investigate whether the pillar can ensure safe production in the mine, the source of goaf water and the direction of water infiltration were analyzed using exploration holes, and it was concluded that the goaf water originated from the V₃ aquifer and was static. Thus, a theoretical analysis was carried out to determine the relationship between the mechanical parameters of the coal and rock structures affected by water. On this basis, a numerical simulation was employed to examine the key changes in the coal pillar and roadway affected by goaf water. The simulation results showed that the plastic area was 6–11 m and the elastic area in the middle was 6–8 m after excavating the working faces on both sides of the coal pillar, and the water flow vector of the aquifer could not pass through the pillar. Finally, in situ monitoring using ground-penetrating radar, deformation measurement, and loosening circle detection revealed that the development degree of internal cracks in the coal pillar was relatively light; thus, the pillar could effectively prevent water damage. These monitoring and analysis methods comprehensively evaluate the stability of the coal pillar and provide a guarantee for the safe mining of the working face.

Quantitative determination of the critical size of inclined coal pillar in old goaf water affected area is of great significance for water damage prevention and safe mining. The critical size of inclined waterproof coal pillar is derived by using theoretical analysis, numerical calculation and field engineering practice for the stability of the waterproof coal pillar in old goaf water affected area of 1303 working face of Dananhu I mine in Xinjiang region. Firstly, a force model of inclined waterproof coal pillar was established to reveal the law that the critical size of the coal pillar increases with the increase of coal seam inclination under the action of asymmetric load. Then, numerical simulation was applied to reveal the dynamic evolution process of plastic deformation-destabilization-destruction of section coal pillar under the influence of mining and single-side water pressure, and the critical size of waterproof coal pillar in study area was determined to be 19.09m. Finally, measures such as pumping and pressure relief and slurry reinforcement were adopted to reduce the deformation rate of the roadway on side of waterproof coal pillar, which ensured the stability of the coal pillar and roadway and the safe recovery of the working face.

To address the challenge of intense pressure manifestation induced by remaining coal pillar from gently inclined multi-coal seam mining, a physical similarity simulation experiment was conducted using microseismic, thermal infrared, and borehole television monitoring. The overlying strata movement process, energy release characteristics, and fracture fractal evolution patterns were systematically investigated. The 3DEC numerical simulation was employed to evaluate the effectiveness of roof cutting measures. The results indicate that the overburden movement can be divided into three stages: formation of remaining coal pillar, suspension and fracturing of interlayer rocks, and subsidence and migration of overburden. The suspension of rock strata and the load transfer from uncollapsed strata are the key factors inducing dynamic disasters. Furthermore, the occurrence of disaster-causing energy events exhibited concentration and suddenness; only two IV high-energy events were recorded, accounting for 3.62% of the total energy, corresponding to the sudden fracturing of rock strata and the collapse of the entire overburden. A threshold of 250 J can serve as a criterion for identifying high-energy disaster events in similar models. Combined with the fractal dimension evolution process of fractures, it followed a pattern of growth, stabilization and renewed growth. After the upper-seam and W1121 working face were mined, the fractal dimension increased to 1.324. It remained within 1.372–1.377 during interburden suspension and reached 1.417 after interburden failure. These changes indicate that repeated multi-seam mining promotes upward fracture-zone propagation, potentially affecting the height of the water-conducting fracture zone. Finally, roof cutting was simulated in potentially hazardous coal-rock zones to evaluate pressure relief. Following pressure relief, suspension and hinging of fractured rock beams were largely eliminated. Overburden subsidence became more uniform, while lateral compression on one side of the panel coal pillar decreased markedly. Compaction within the goaf also became more uniform. These findings provide a theoretical basis for safe and efficient multi-seam mining and dynamic hazard control in mines with similar conditions.