Scale Effect of Filling on Overburden Migration in Local Filling Stope of Longwall Face in Steeply Dipping Coal Seam

The gangue filling mining method is used to reduce the occurrence of dynamic disasters on the roof of a steeply dipping coal seam (SDCS) effectively and improve the stability of the overburden structure. To comprehensively study the movement law of the overburden under different filling quantities, the 3221 working face of the Lvshuidong coal mine was taken as the research site. The vertical displacement, vertical stress, and plastic zone of the overburden under different filling quantities were analyzed by using FLAC3D numerical simulation and physical similarity simulations. The results show that the maximum stress in the stress concentration zone decreased with the increase of filling size. The vertical stress range of the overburden and floor in the filling zone increased significantly. The affected zones of the vertical displacement of the roof and floor and the vertical displacement of the overburden were reduced to varying degrees. The overall plastic zone was shrinking. The movement of overburden was well-controlled as the proportion of the fillings increased. The results of this study can provide an important reference for the stability control of the roof of SDCS filling mining.