Abstract：The stability of the talus slope，which is located at the left riverbank ahead of the dam of Zipingpu hydraulic project，is extraordinarily important during the reservoir operation. Based on field investigation，the geologic background and structure character of the talus slope have been fully analyzed and specified. It is judged that the talus slope is just in the stage of slow creep deformation currently by the evolutionary rule of the slope. The chief controlling stability factors are the reservoir water effect and the earthquake effect under the reservoir working condition. And the mechanism of the reservoir water and the earthquake action to the slope are also analyzed. The paper focuses on the deformation and failure mechanism of the talus slope. The phenomenon of superficial creep deformation and submerged failure would arise and there would be four failure patterns of the talus slope during the reservoir operation. The merits and defects of the yield criterion are discussed，which are Mohr-Coulomb yield criterion and generalized Mises yield criterion used extensively in slope engineering. And the instability criterion is comprehensively analyzed. The specific criterion indexes are put forward by the convergence criteria. And then the location and shape of the most unfavourable slide surfaces are determined by the theory of strength reduction，which are located at the front slope of Dengzhan plateau. The stability of four failure patterns of the talus slope is researched by limit equilibrium method under various work conditions. The research results indicate that the local failure of the front slope of Dengzhan plateau would happen firstly and then the global failure of the talus slope would induce under the reservoir water drawdown conditions. Main attention should be paid to the stability control of the front slope of Dengzhan plateau.
