Mechanism of Water Inrush Through Fault Zones Using a Coupled Fluid–solid Numerical Model: A Case Study in the Beiyangzhuang Coal Mine, Northern China

To better understand the mechanism of water inrush from fault zones, we investigated a typical inrush case from a coal mine in northern China, identified the water source and the role of fault zones, and analyzed the mechanical characteristics of the rock mass. We established a numerical model of fluid–solid coupling using finite difference methods based ideal elastic–plastic and Biot’s consolidation theories. The model considers softening effects caused by mine dewatering as well as the dynamic influence of mean principal stress and pore water pressure on fault zone permeability. It also simulates fault zone deformation, failure, and seepage under natural and disturbed-state conditions. The mechanism of water inrush through fault zones in a disturbed area was identified by comparing the deformation, failure, and seepage characteristics of fault zones with and without disturbance. The results show that deformation was concentrated at the bottom of the fault zone because of its naturally low strength, which created favorable conditions for water inrush. Softening of the media by mine dewatering also facilitated water inrush. Feedback effects between the fault zone and groundwater-enhanced permeability then led to groundwater bursting into the mine through the fault zone. This study provides an important framework for groundwater hazard prevention in similar mining areas.