Abstract:
Regional treatment through surface high-pressure grouting is one of the primary prevention and control measures for safe coal mining beneath thick and loose confined aquifers. However, the high-pressure grouting process can induce movement and deformation of the overlying strata, leading to local surface uplift and structural deflection in the mining area. This phenomenon is a critical concern in the safety management of regional grouting transformations. Based on the engineering context of grouting transformations in a water-rich sandstone beneath the roof covering at working surface 120501 of a mining area in Anhui Province, this study employs numerical simulations utilizing the COMSOL Multiphysics finite element method. It investigates the process and temporal evolution characteristics of the overlying strata before and after high-pressure grouting. Furthermore, a distributed fiber optic full-section monitoring system is constructed to assess the deformation characteristics of the overlying strata at various depths and their influence on surface disturbances. The findings indicate that the regional high-pressure grouting process can be delineated into three distinct stages: “filling” “diffusion” and “disturbance”. The filling stage exhibits minimal disturbance to the overlying strata, whereas the diffusion stage generates horizontal disturbances. During the disturbance stage, significant vertical displacements are observed in the overlying strata. The influence of grouting on formation disturbance during the reconstruction process follows an increasing trend represented by a Logistic curve. The primary impact of disturbance occurs in the lower sections of the thick loose layer, with vertical arching observed predominantly in the relative water barrier section and compression occurring in the aquifer section. Monitoring results reveal that the deformation characteristics throughout the grouting process are nonlinear, with the sandy clay strata and silty sand strata identified as the primary contributors to deformation. The outcomes of full-section monitoring and numerical simulations align well. The results can offer insights and practical references for ensuring the safe operation of coal mines and effectively preventing and controlling secondary disasters triggered by regional grouting in the eastern thick loose layer covered mining area.