Dynamic stability and failure mode of slopes with overlying weak rock mass under frequent micro-seismic actions

The micro earthquakes with high frequency induced by reservoir filling may exert an influence on the stability of bank slopes. Based on Shanshucao landslide in the Three Gorge Reservoir area,the shaking table tests and the discrete element method (UDEC) are used to analyze the dynamic response, cumulative damage process and failure modes of a typical slope with overlying weak rock mass under frequent micro-seismic actions. The results are as follows: under the actions of frequent micro-seism, the natural frequency of vibration of the model slope reduced gradually, whereas its damping ratio continues to raise, which shows the decrease of rock integrity. During the initial stage and the micro-seismic action stage, the acceleration response of the slope is characterized by“elevation effect”and“aspect effect”, while the results begin to deviate as the small seism is louded. The failure evolution process of the model slope can be summarized as “development of the secondary joints→extension of the secondary joints→breaking of the upper rock mass→expansion of the rear crack→formation of the slip plane→failure of the slope”. The discrete element numerical results show that the deformation of the slope with overlying weak rock mass under frequent micro-seismic actions mainly occurs in the upper rock mass, which is above the rock interface and below the rear crack. With the increasing number of earthquakes, the permanent deformation of the slope continues to enlarge, and its stability coefficient decreases simultaneously, which is accordant with the results of the shaking table tests.