Experimental Study on the Characteristics of Concealed Faults’ Activation and Conduction under Two Layer Confined Aquifers Underlying Coal Seam Floor

Abstract

Purposes The existing researches on mining induced water inrush through concealed faults underlying coal seam floor only consider the condition of single confined aquifer under coal seam floor. The activation characteristics of water inrush through concealed faults under the condition of two layer confined aquifers need to be studied. Methods The mining stress and pore pressure evolution of concealed faults at different depths during mining were analyzed by means of similar physical simulation. Findings The results show that the self-designed water inrush test system can reasonably simulate the faults’ activation and conducting law at different depths under the condition of two layer confined aquifers. The change degree of mining stress and pore pressure increments in shallow fault zone is higher than that of deep fault zone, and the change time of pore pressure lags behind the change time of stress. At the end of mining process, the increasing trend of pore pressure increments in shallow and deep fault zones reflects that the unloading of fault zones to the goaf promotes the development of seepage. There is a possibility of delayed water inrush in fault zones, and the risk of delayed water inrush in shallow fault zones is relatively higher than that of deep fault zones. The degree of stress disturbance decreases with the increase of depth, and the shallow part is more likely to be activated than the deep fault zone. Continuous disturbance will generate the hydraulic connection between the shallow and deep aquifers, the deep confined aquifer can recharge the shallow confined aquifer through the concealed fault, and there is significant head pressure loss in the process of confined water inrush through fault zones. Conclusions The results can provide theoretical and practical reference for the analysis of concealed fault’s activation and conduction mode under the condition of multiple confined aquifers underlying coal floor.

Keywords

• coal seam floor
• concealed fault
• two layer confined aquifers
• activation and conduction
• experimental study