Study on the Transmission Mechanism and Evolution Law of Surface Deformation in Abandoned Goafs Under Groundwater Action

Abstract

The intrusion of groundwater inevitably alters the environment within the caving zones of mined-out areas and affects the mechanical properties of the surrounding rock mass, thereby influencing surface deformation. To investigate the deformation mechanisms of overburden and surface under the influence of groundwater in caving zones, as well as the deformation patterns of abandoned mined-out areas under different geological and mining conditions, this study takes a coal mine in Jiangsu Province, China, as a case study. Based on FLAC3D (version 6.00) numerical simulations, the study analyzes the mechanisms and main influencing factors of overburden and surface movement in abandoned goafs under groundwater conditions. It further examines the deformation patterns under groundwater intrusion and explores the effects of different mining thicknesses and weakening of caving zone parameters on surface deformation. The results show that the weakening of mechanical properties leads to subsidence of the overburden and surface, while increased pore water pressure reduces effective stress, causing initial subsidence followed by uplift. Moreover, under varying conditions of coal seam thickness and weakening intensity of the caving zone, surface deformation in response to groundwater in abandoned goafs exhibits distinct patterns. These findings provide a theoretical basis for scientifically interpreting the propagation mechanisms and movement characteristics of surface deformation in abandoned mines under hydro-rock interaction.