Stability analysis of overlying rock strata on the deep inclined mining face of "three soft" coal seam

To address the problem that the overlying strata structure is prone to instability and induces dynamic disasters during mining in deep gently inclined working faces of "three-soft" coal seams, we take the 130207 fully mechanized mining face as the engineering background. By comprehensively using theoretical analysis and numerical simulation, it studies the overlying strata failure and stability control mechanism under the coupling effect of deep high in-situ stress, gently inclined occurrence, and soft coal-rock mass. The results show that: the heights of the caving zone and fractured zone of the working face are 8.30–11.30 m and 22.85–30.85 m, respectively, and the soft immediate roof significantly controls the fracture development morphology; the breakage of medium-grained sandstone, which acts as the key stratum, is the key factor that triggers structural instability of the overlying strata and determines the development height of the “three zones”; a stress concentration zone exists 12 m ahead of the coal wall, with a concentration factor of 2.78, and bed separation below the key stratum develops significantly. This study clarifies that key stratum breakage is the main cause of overlying strata instability and stress redistribution.