Abstract: A case of water inrush through fault induced by mining in Zhongguan iron mine was studied by the finite element simulation. The fault stress and damage zones were analyzed to study the mechanism of fault reactivation-induced water inrush. The simulation results illustrate that the excavating process is the cause of damage zones initiation， accumulation， extension and coalescence. The fault shear stress concentration moves from the top downward to roof gradually. The compression-shear damage zone in the fault changes to tension-shear damage zone and grows gradually. When the fault is fully exposed， the connected damage zone provides a channel for the groundwater outburst and finally causes the inrush incident. Therefore， the conductivity of the natural waterproof fault cannot be completely confirmed by horizontal cover hole before excavations. To be safe， more acclivitous cover holes should be drilled to probe the conductivity of the fault in the higher positions for the further confirmation.

Key words: excavation, fault reactivation, water inrush, numerical simulation, Zhongguan iron mine