Cause analyses and prevention suggestions for the karst collapse in the Fujia village of Hunan, China

Based on the theory of karst ground collapse, this work studied the genesis and development trend of the karst ground collapse at the Fujia Village, Ningxiang Coal Mine. Previous surveys show that high distribution density, large collapse scales, poor stability after backfilling, and continual deformation or even collapse again characterize the study area. Analysis of the geological environment conditions reveals that the thickness of the cover layer is relatively thin and karst is developed in this area. Meanwhile a huge falling funnel formed in the drainage of the coal dam mining area. Furthermore, a vast large hydraulic gradient is present between the pore water and karst water, which leads to the occurrence of karst ground collapse in the area. At the same time, a huge goaf formed in the limestone mine within this area, which has greatly promoted the occurrence of karst ground subsidence. And its functions are as follows. First, it provides a huge material storage space. Second, it greatly reduces the material migration path. The soil in the area is transported by the erosion of groundwater. The upper soil loses its support and continuously flows into the goaf, resulting in poor stability after backfilling of the pit and the collapse of the old collapsed pit.