Pressure Relief Effect of Overlapping Mining of Upper Protective Layer with Large Spacing

The first mining area of Pingmei No.8 mine was selected as the research object, through FLAC3D numerical simulation method combined with field measurement results of drilling cuttings, the protection effect of large spacing upper protective layer on lower coal was analyzed. The research results show that the pressure relief effect of group Ⅳ coal seam mining on group Ⅴ coal seam is 42%, and the inclination pressure relief angle is 75° on the lower side and 65° on the upper side, which has a certain pressure relief protection effect, and the decompression effect on group Ⅵ is 6%, but the decompression effect is not obvious; decompression effect of group Ⅴ mining on the coal seam of group Ⅵ is 17%, and the inclination pressure relief angle is 77° on the lower side and 71° on the upper side; the decompression effect was further enhanced after the joint mining of Ⅳ-Ⅴ, and the decompression effect of Ⅳ-Ⅴ on the coal seam of the group Ⅵ was 20% after Ⅳ-Ⅴ mining, and the inclination pressure relief angle is 77° on the lower side and 72° on the upper side; the overlapping and staggered layout of the spatial projection on the working face of each coal group makes the pressure relief zone of group Ⅳ and group Ⅴ play a role of mutual shielding in the mining process, eliminating the influence of stress concentration and playing a good protection role for the coal seam of group Ⅵ.