Strata movement law and stress distribution characteristics of deep multi-coal seam mining in Yingpanhao Coal Mine

The Dongsheng Coalfield in Ordos is a Jurassic coal bearing formation, and the 2-2 and 3-1 coal seams in many deep mining areas can be mined in the whole area, and the spacing of coal seams is small. This paper takes Yingpanhao Coal Mine as a geological prototype, and constructs a numerical model of the research area through FLAC3D and UDEC numerical simulation software to study the surface movement deformation and the evolution law of stress field caused by mining coal seams 2-2 and 3-1. The results show that repeated mining in multiple coal seams will cause the central projection of the subsidence basin to move toward the direction of lower coal seam, and then approach the central projection of the initial mining of the upper coal seam, and ultimately cross it; after the two coal seams were continuously mined, the maximum subsidence value of the surface is less than the sum of the maximum subsidence values caused by mining the two coal seams separately, and the subsidence coefficient of the coal seam repeated mining is less than the initial mining subsidence coefficient; coal pillar dislocation is closely related to surface movement parameters, the staggered coefficient is related to the surface subsidence coefficient, horizontal movement coefficient, and the tangent of the main influencing angle in a logarithmic normal function, concave parabolic function, and convex parabolic function, respectively; as common factors, pillar staggered distance and width-depth ratio have coupling effects on the ratio of characteristic parameters of primary mining and repeated mining in coal seam; in addition, with the increase of pillar staggered distance, the surface subsidence basin area decreases first and then increases, and the contours of horizontal movement near the basin evolve from ellipse to shuttle; the optimal staggered distance of multi-coal seam mining in this study area is 30 m based on the empirical formula of pressure relief distance, the surface damage degree and the relief effect of staggered mining.