Abstract: Under strong earthquake action, plastic zone penetrates through rock slope and makes it unstable. Encountered with external forces these unstable slopes are likely to become lagged landslides. In the present research we established a numerical model using finite element software ANSYS to simulate an unstable slope after Wenchuan earthquake. The simulation revealed that joint surfaces changed a lot after earthquake waves passed through, the movements of rocks on two sides of the joint surface were different; the internal shear stress and tensile stress of rock bridge fluctuated heavily, which induced the penetration of plasticity; the contact sliding distance distributed very unevenly, and the dynamic responses of different positions of joints were quite different. Finally, according to engineering geological survey results and characteristics of unstable slope, we identified the potential sliding surface, and proposed treatment measures including crack-grouting and slope-cutting.

Key words: lagged earthquake-induced landslide, failure mechanism, numerical simulation, time-history curve of displacement, prevention measures