Study on overlying strata migration law of strip interval filling mining

Aiming at the problem that it is difficult to popularize in Guizhou mining area due to high filling cost, taking 11071 working face of Panzhihua Coal Mine in Liupanshui as the research background, the idea and technology of strip interval filling mining are put forward. Through theoretical analysis and mechanical tests, the reasonable range of strip spacing distance and mechanical parameters of filling body were obtained. The FLAC3D simulation software is used to analyze the stress field, displacement field, and plastic zone of five kinds of design schemes, and the UDEC simulation software is used to carry out the filling mining of No.7 coal seam. The results show that the strip interval filling mining technology regards the empty roof area as a controllable underground spatial structure, and the single spatial stress field changes little. The load on the immediate roof is gradually transferred from the top of the empty roof area to the top of the filling body. The "filling body-direct roof" structure improves the self-bearing capacity of the immediate roof, and the overlying surrounding rock migration is controlled. With the increase of mining depth, it gradually tends to the original rock stress, and the control effect on surface subsidence is more significant. Finally, "filling 3 m interval 3 m" is determined as the optimal filling scheme. In the process of simulated filling mining, the peak stress in the stress concentration area of the front coal wall shows a trend of "increase-decrease-increase," and the peak stress curve of the immediate roof in the middle of the stope changes from "increase-decrease 'trend to' increase-decrease-increase-decrease" trend. The rock layer near the immediate roof is in a stress concentration state in the coal wall area on both sides, and the middle part is not obvious.