Study on roof activity and surface subsidence law under the condition of continuous small coal pillar mining

Taking the 3104, 3106 and 3107 working faces of Menkeqing Coal Mine as the background, the comprehensive microseismic and surface subsidence monitoring research are found that in the roof activity of large goaf in continuous small coal pillar mining, the roof movement of 3107 working face does not disturb the adjacent overburden rock in the early stage of mining. With the advance of mining, only 3104 overburden rock is affected, and 3106 overburden rock has no significant effect. The microseismic event jumps from 17.35 m fine-grained sandstone above the coal seam roof to 30 m siltstone and finally to 48.05 m coarse-grained sandstone, showing a trend of high-level rock migration. The surface settlement shows that the maximum settlement is concentrated on the side of 3107 return airway, the extreme point of settlement is shifted from the middle of the mining area to the 3104 goaf, and the settlement in the middle of the 3106 goaf tends to be stable. The monitoring line reveals that the maximum subsidence point is shifted to the goaf, which confirms that 3107 mining induces the secondary subsidence of the large goaf.