Study on the evolution mechanism of gangue filling and overlying rock spatial structure in steeply dipping stope

•The evolution process of macro structure of overlying strata in steeply dipping stope is analyzed.•The basic characteristics and evolution mechanism of the spatial bearing arch shell are clarified.•The evolution of stress and deflection response law of surrounding rock in stope are analyzed.•The influence mechanism of gangue on the spatial structure and mining dynamic behavior of surrounding rock in steeply dipping stope is revealed. The key to the safe and efficient mining of steeply dipping coal seams is the effective control of surrounding rock, and the discovery and revealing of the evolution mechanism of the spatial structure of overlying strata is the basis for the stability control of surrounding rock. By means of theoretical analysis and physical experiment, the evolution characteristics of the spatial structure of overlying strata in steeply dipping stope are clarified. Combined with numerical calculation, the stress evolution and deflection law of overlying strata are analyzed, and the influence mechanism of gangue on the spatial structure of surrounding rock and mining dynamic behavior is revealed. The results show that under the influence of unbalanced filling of gangue and key strata, the spatial bearing structure of steeply dipping has undergone multiple evolutions, showing a plate-shell combined step structure, and the size of key strata is affected by the evolution of overburden structure. The filling gangue changes the stress transfer path of the surrounding rock of the stope. There are two stress deflection boundaries in the rock strata, and the peak value of the abutment pressure is transferred to the lower part of the non-filling area. The principal stress deflection angle gradually decreases from the goaf to the boundary on both sides. The change rate of the principal stress difference and the shear stress of the rock strata decrease with the increase of the principal stress deflection angle.