Abstract:In order to accurately grasp the evolution and distribution law of overlying strata fissures in extra-thick coal seam mining in Jingyuan mining area, and provide a basis for the layout of gas extraction system in the course of mining, the north 1103 working face of Weijiadi mine was taken as an experimental prototype, by means of combining physical similarity simulation with UDEC numerical simulation, the mining test of working face is carried out, and the law of cyclic weighting of overlying strata in extra-thick coal seam is calculated, and the variation law of surrounding rock stress during mining is analyzed, the evolution and distribution law of mining fracture in extra-thick coal seam is studied. The results show that the fracture zone and the collapse zone stop developing upward at the last periodic weighting, the heights are 39.1m and 127.9m respectively, and the stress distribution in the stress concentration zone of the surrounding rock is axisymmetric, the distribution range is 8.94MPa something 19.8MPa, the stress distribution in the pressure relief area is parabola, and the distribution range is 0.22MPa something 1.46MPa. The height of the pressure relief area and the height of the maximum displacement area gradually increase with the increase of coal seam mining height, and the increase trend of the height of the pressure relief area tends to be slow, the variation range is 70.4m something 81.2m, the height ofmaximum displacement area is 52.4m something 74.8m, its width decreases with the increase of mining height, and the variation range is 102.3m something 71.6m, the main key stratum has obvious subsidence deformation, no obvious fissure above, fissure surge below, the width of compacted area in goaf decreases and the height increases.
