Study on fractal dimension of coal pillar fracture in mining section of short-distance coal seams

In order to study the compression and stability of coal pillar of short-distance coal seams under downward mining, take the short-distance coal seams in Ningtiaota Coal Mine as the research object, through the edem simulation test, FLAC^3D numerical simulation, coal pillar strength theory and method combining fractal theory, the paper investigated the ultimate maximum compression of safe stability of the sectional coal pillar and its horizontal fractal dimension. The research showed that the peak stress and vertical displacement of coal pillar decrease with the increase of the staggered distance between two sectional coal pillars. The fractal dimension of horizontal section fracture also accordingly decreases. When the staggered distance of the coal pillar reaches 40 m, the central peak stress and vertical displacement of the sectional coal pillar in upper 1^-2 and lower 2^-2 coal seams are less than the ultimate compressive strength and the maximum compression of the coal pillar. It is revealed that the compression and peak stress of the sectional coal pillar vary with the staggered distance of coal pillar and given the corresponding relationship between fractal dimension of horizontal section fracture of 2^-2 seam section coal pillar and coal pillar stress with its staggered distance.