Abstract: According to Dagushan open-pit mine broken zone of stability issues in rainstorm, hydraulic characteristics on the impact of the stability was simulated by FLAC2D.The  results show that the content of clay mineral is largely influenced hydraulic characteristics of rock, high content of clay mineral reduce its water stability, thus affecting the its stability.With water content increase, the slope of strength reduced gradually.Factor of safety also decrease with the increase of water content.When the moisture content reaches 7.39%, factor of safety is 1, and the slope is in limit equilibrium state.When the moisture content is larger than 7.39%, the slope failure happens.

Key words: Open-pit mine broken zone, Moisture content, Factor of safety, Numerical simulation