Abstract：Rock mass of arch dam abutment in a hydropower station is incised by a key fault. So the abutment is possibly instable under the combined action of huge water pressure and the disadvantageous geologic setting，and it is a key factor to control the safety of the whole project. In order to study the stability，a nonlinear 3D numerical simulation is conducted for rock mass in arch dam abutment incised by fault. Stability is studied by point safety factor method and overload method. Enhancement on key fault is simulated，and the influence on the stability of rock mass in abutment is analyzed. The results show the stability is increased evidently after fault enhancement，and thus it can provide reference to engineering practice.
