Numerical Modeling of Non-Darcy Flow Behavior of Groundwater Outburst through Fault Using the Forchheimer Equation

In a groundwater outburst through a fault, the velocity is generally so high that the relationship between the velocity and the hydraulic gradient deviates from the linear Darcy regime. This study uses the Forchheimer equation to model the flow in both the aquifer and the fault zone. The model is used to investigate the effects of non-Darcy flow on a specific inrush episode at the Zhongguan iron mine by varying the fault permeability. It shows that the flow behavior in the aquifer was not always Darcy flow or non-Darcy flow, but changed depending on the fault permeability. The region in the aquifer near the fault is most likely affected by non-Darcy flow, and the non-Darcy-effect region expands away from the fault with the increase of the fault permeability. Considering a 10% non-Darcy effect for engineering, the Forchheimer equation can be approximately used to describe the flow mechanism from Darcy to non-Darcy. Furthermore, the Forchheimer equation is also acceptable for predicting the groundwater inflow during groundwater outburst through fault.