Research and practice of the synergistic control mechanism of three-dimensional filling in deep coal seams

To ensure the safe extraction of coal resources beneath surface buildings, a collaborative roof control technology integrating underground filling mining and surface key strata grouting was implemented at the 11213 and 11235 working faces of Xingdong Mine, Jizhong Energy Group Co., Ltd. (hereinafter referred to as Xingdong Mine). A synergistic control mechanism of overburden movement based on underground and surface three-dimensional filling was proposed. Furthermore, a subsidence coefficient for filling mining incorporating the filling ratio parameter was derived, and the basis and selection method for determining the final grouting horizon in overburden fractures were established. Numerical simulations of overburden fracture development indicated that, following coal extraction, the separated layer space beneath the lower sub-key stratum underwent a dynamic spatial evolution process, successively exhibiting a linear configuration and a crescent-shaped configuration. Based on these evolution characteristics, the optimal timing for the initial grouting operation and subsequent cyclic grouting during working face advancement was determined. A set of key technologies and a production mode for integrated underground and surface three-dimensional filling were established. Surface deformation monitoring under different mining conditions demonstrated that the maximum surface subsidence rate and the maximum surface subsidence were only 0.24 mm/d and 167.9 mm, respectively, indicating that the proposed three-dimensional filling technology achieved effective control of mining-induced surface subsidence.