Depth-dependent mechanical-seepage behavior and safety mining distance of the steeply inclined coal mine underground reservoir

• A novel SICMUR framework is proposed where the coal seam itself serves as the reservoir floor, challenging conventional CMUR designs. • Triaxial tests show a 3.5 MPa strength increase per 100 m depth and a 58-fold post-peak permeability surge at 300 m vs. 100 m, highlighting depth-dependent behavior. • Similar simulations reveal significant mining-induced stress redistribution and deformation, with a minimum 40 m safety distance required between reservoirs and lower coal seams. • Critical construction parameters for Wudong mine SICMUR include collapse zone heights of 9.9–12.31 m and water-conducting fracture zone heights of 31.96–37.40 m.