Pressure reduction mechanism and effect of working face passing through abandoned roadway by roof presplit

Due to the existence of abandoned roadways in the thick coal seam, the ground pressure would increase greatly due to the roof advanced breaking when the working face passed through the affected area of abandoned roadways. In order to solve this problem, a solution for roof presplit in the abandoned roadway was proposed. Based on the mining and geological conditions of Huasheng Hufeng coal mine, the roof vertical stress and vertical displacement with different roof presplit distance were analyzed by using FLAC3D numerical software. The research results indicated that the roof vertical stress and vertical displacement could be reduced effectively by roof presplit. When the roof presplit distance was 15 m, the maximum vertical stress and the maximum vertical displacement were both minimum. The maximum vertical stress was reduced by 14.55% and the maximum vertical displacement was reduced by 37.51% after roof presplit. The reasonable roof presplit distance of the working face was determined to be about 15 m by combining theoretical and numerical analysis. The engineering application results indicated that the maximum working resistance of the hydraulic support was reduced by 35.86% after roof presplit, and the engineering effect was good. The research results can provide technical guidance and theoretical support for the same type mines.