Abstract: Dynamic stability evaluation and failure mechanism research were performed on the Yanyang village landslide along Xiangli expressway in Yunnan province. The landslide stability analysis under different seismic intensities was carried out, the progressive failure of landslide was described by the change in volume ratio of residual elastic zone of slip zone. The dynamic stability of landslide was evaluated by combining with the deformation mode of landslide and the volume ratio of residual elastic zone. For the failure mechanism of landslide under extreme earthquake conditions, the failure process of landslide was described in terms of time and space respectively. A cusp catastrophe model of landslide, which could consider both weakening and hardening section of slip zone, was established and the trigger mechanism was revealed. The results showed that: (1) the landslide under the condition of Ⅷ degree seismic intensity remained stable, and only local failure occurred due to the "locking effect " of locking section; (2) The critical peak acceleration of overall failure of the landslide was 2.29 m/s2, and its failure mechanism was the whole failure caused by the sudden penetration of the plastic zone due to the failure of "locking action" under the coupling action of leading section traction and trailing section tension crack; (3) The leading, middle and trailing section of the slide zone were not destroyed synchronously, but presented a cumulative-triggering process. (4) A failure criterion of stiffness effect was derived based on the improved cusp catastrophe model, the overall stability of the landslide was found to be closely related to the stiffness and size characteristics of the sliding zone medium. The results could offer guidance for disaster prevention and seismic design of Yanyang village landslide, and be used for reference in the dynamic stability evaluation and failure mechanism analysis of similar projects.

Key words: landslide, earthquake, dynamic stability, locking effect, cusp catastrophe model, trigger mechanism