Damage evolution and delayed groundwater inrush from micro faults in coal seam floor

Based on the knowledge of solid-fluid coupling mechanism and strength degradation law of coal seam floor,numerical tests with FEM method are conducted to investigate the long-term characteristics of floor rock mass and the initiation of fractures,activation of faults and formation of groundwater inrush pathways based on the mechanic model for rock mass with weak faults in coal mining above the confined aquifer.With the understanding of stress,damage and seepage flow evolution,the transformation of floor rock mass from water-resisting strata to inrush pathways is clearly illuminated and the groundwater inrush pathways are calibrated.Furthermore,the influence of the height of faults and the magnitude of water pressure on the damage evolution and delayed time of groundwater inrush is studied.And some significantly meaningful guides are provided for the investigation on the mechanism and prevention of delayed groundwater inrush in practice.