Experimental and numerical investigations of concealed fault zones’ activation characteristics with multiple confined aquifers underlying coal floor: a case study from Shanxi, northern China

This study conducted a physical experiment and numerical simulations to investigate the evolution of stress, pore pressure and activation characteristics of concealed faults with two-layer confined aquifers underlying coal floor during mining. The physical experimental results show that the increment change rate of pore pressure lags behind the change in stress, and the change degree of stress and pore pressure increments in the shallow fault zone is higher than that of the deep fault zone. The water inrush risk of shallow fault zone is higher than that of the deep fault zone. Numerical simulation results show that the degree of stress disturbance decreases with the increase of depth, and the activation of the deep fault zone lags behind the shallow part. The distribution of pore pressure in various locations indicates varying degrees of activation in the fault zone. Mining disturbance can generate hydraulic connections between shallow and deep aquifers, and concealed faults can facilitate the recharge of shallow confined aquifer through deep confined aquifer. It is crucial to avoid or mitigate disturbance to the deep fault zone. The results can provide theoretical and practical reference for the analysis of concealed faults’ activation characteristics under the condition of multiple confined aquifers underlying coal floor.