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采用FLAC3D对衡山县石膏矿闭坑前后空区引发的地面塌陷机理进行了分析,并对该矿不同采场结构参数的地表沉陷进行了模拟。研究结果表明:该矿闭坑后采空区顶板和矿柱的最大位移分别是闭坑前的7倍和10倍;闭坑前矿柱已严重破坏,闭坑后矿柱不足以支承上覆围岩压力而引起采空区顶板垮落,形成垮落拱;采空区边界的围岩受顶板垮落的影响,产生应力集中,造成其沿采空区边界整体剪切滑移失稳,进而诱发顶板整体垮落,最终在地表形成“漏斗型”塌陷区;地面塌陷区的影响范围距采空区边界约80m;矿房跨度为10m、矿柱跨度为4m是该地区石膏矿最合理的采场结构参数。
FLAC3D was used to analyze the mechanism of ground subsidence induced by the closed pit before and after the closure of the gypsum mine in Hengshan County. The ground subsidence caused by different structural parameters of the mine was simulated. The results show that the maximum displacements of roof and pillars in the goaf after closed pit are 7 times and 10 times that of the closed pits respectively. The pillars have been seriously damaged before the pits closed and the pillars are not enough to support the overburden The pressure of surrounding rock causes the roof of the goaf to collapse and form the caving arch. The surrounding rock of the gob area is affected by the caving of the roof, resulting in stress concentration, which causes the shear sliding instability along the boundary of the goaf, And then induced the roof to collapse as a whole, eventually forming a “funnel-type” subsidence area on the surface; the influence range of ground subsidence area was about 80m away from the boundary of the goaf; the mine span was 10m and the pillar span was 4m. The most reasonable stope structure parameters.