Theoretical and numerical investigations on mining-induced fault activation and groundwater outburst of coal seam floor

Mining activities carried out above an aquifer, especially in the hanging wall of normal faults, generally involve the risk of water inrush. For a better understanding of the mechanism inducing groundwater outburst through fault floor, the analytical and numerical simulation methods were applied to investigate the process of fault activation driven by mining and hydraulic loads. The influences of the advancing distance and fault dip were conducted. The results exhibit good agreement between the theoretical calculation and the numerical simulation. The fault activation by induced tangential stress change has a positive correlation with the advancing distance and a negative correlation with the fault dip angle. The stress concentration factor increases significantly when the excavation process enters the horizontal range of fault projection, following the stress peak and failure zone approaching the coal seam from deep to shallow along the fault. For the cases with a constant advancing distance, the smaller the fault dip is, the earlier the water-inrush channel will be formed. The research results in this study reveal the theoretical mechanism of fault activation and groundwater inrush of coal seam floor above a confined aquifer and thus provide valuable insights for the prevention and risk assessment of mine water disasters in underground engineering.