Study on Water‐Rock Coupling Damage Mechanism and Water Inrush Prevention and Control of Overlying Coal Seam in Karst Confined Aquifer in Karst Area

ABSTRACT To solve limestone floor water inrush and reduce accidents, this paper studies Fengxianglin Coal Mine. It uses field investigation, mechanical experiments, similar simulation and engineering numerical simulation to explore limestone floor damage, Maokou Formation fracture development, and the influence of advancing distance, coal seam burial depth, aquitard thickness and floor water pressure on floor water inrush during coal—seam mining above confined water. Results show that stress—strain curves of limestone with different water content have four stages: initial stress growth, crack compaction, stress increase and stress drop. Water dissolution softens limestone, enhances nonlinear deformation and changes failure mode from local brittle to overall plastic. The coupling of pore water pressure and mining stress reduces floor strata strength and raises water inrush risk. Digital image correlation (DIC) technology monitoring shows that in the process of working face advancing. The maximum principal strain concentration range and degree of strata gradually expand. The strain distribution is ‘W’ shape, and the displacement curve is irregular ‘M’ shape. Water inrush occurs when the floor damage zone connects with the aquifer water channel. Numerical simulation reveals that increasing advancing distance raises floor fractures and pore pressure. Pore pressure distribution changes from inverted ‘circular arch’ to inverted ‘concave’ with increasing coal seam burial depth. Increasing aquitard thickness reduces pore pressure and inhibits fracture propagation. Increasing floor water pressure accelerates crack propagation and heightens water inrush risk.