Research on mechanism of control surface subsidence by underground key isolation layer filling and its application

Large-scale goaf appeared after underground mining, and the widespread connection of the goaf is main reason causing surface subsidence. Surface subsidence is a serious engineering geological disaster impacted on ecological environment, which has plagued the underground mining enterprises at home and abroad. In order to ensure safety mining of the deep level and effectively control surface subsidence, the method of filling key stress isolation layer was firstly proposed and the stress was isolated by whole filling at a reasonable level before the deep level mining. Then taking the case of a gold mine, the overall mining and filling process at different deep levels were simulated with three-dimensional finite element analysis software (3D-σ),and the mechanism of filling key isolation layer controlling rock strata movement and surface subsidence was thoroughly studied. It was found that the two main factors of controlling surface subsidence are the level of filling isolation layer and the filling volume of goaf. The goaf-volume balance method was proposed to determine the optimal filling level and the best filling time. Finally, field test was carried out in the underground gold mine. It was verified that the method of filling key isolation layer was feasible to control surface subsidence, field monitoring data agree well with the simulation results, effective protection the vertical shaft safe operation. The method of filling key isolation layer control surface subsidence could protect the safety of the vertical shaft, which could be further applied to relevant projects and reduce the occurrence of geological disasters in mining engineering.