Hydropower plants (including the switching station) built in the middle and southern section of the north–south zone of China are always situated in complex geological settings of transition zones from strong to weak earthquakes with active faults. It is of great importance to carry out careful evaluation of the slope stability considering various loading scenarios to ensure safe operation of the power stations. By using the rigid body limit equilibrium method and the finite element method, the effects of long-term load and seismic load on slope stability for a large hydropower station were studied. The results show that the slope safety factors of the station meet the stability requirements when the slope is under long-term load and under the action of the Wenchuan and Lushan earthquake loads. The stability of the slope is guaranteed. However, the risk analysis of the slope stability under the action of the design earthquake load shows that the slope safety factor is less than the accidental working condition safety factor of 1.05. Under the action of a strong earthquake, the crumbling block gravel soil layer in the shallow natural slope slides and destabilizes, which is obviously beyond its protection capacity, and therefore, effective seismic defense measures should be developed to ensure the safety of the personnel and equipment operating in the power station and switching station.

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