Study on the impact of stress effects on gas extraction in thick inclined coal seam caving faces

In order to study the development of overburden fractures and the distribution characteristics of the “three zones” in extra-thick coal seams, a rota-table physical similarity simulation test platform was used to analyze the deformation and failure characteristics of overburden during the mining of extra-thick coal seams. The displacement patterns of key layers were measured under different excavation distances. A statistical analysis of the overburden fracture distribution was conducted, revealing the evolution characteristics of fracture development in the overburden with increasing advancing distance. Stress changes in key layers during excavation were also recorded and analyzed. By combining the study of the influence of overburden fracture development on gas migration, the mechanism of elliptical paraboloid-shaped fracture zones formed by mining-induced overburden fractures in extra-thick inclined coal seams was identified. A method for arranging directional high-level long boreholes based on fracture development characteristics was proposed. In field practice, the average pure gas drainage volume increased from 3.40 m3/min to 5.70 m3/min, showing a significant improvement in drainage efficiency.