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In a strong earthquake, not only a large number of coseismic landslides are triggered, but relaxation and cracks in the rocks and soils are induced, which make these rocks and soils vulnerable to instability during subsequent rainfall; thus, strong earthquakes always have long-term effects on landslides. The geo-hazards along the Zhaotong-Qiaojia road in the 2014 Ludian earthquake (Ms 6.5) of Yunnan Province, China, were investigated, and the Ganjiazhai giant landslide was chosen as a case study. First, using the limit equilibrium analysis and Newmark method, the critical seismic intensity of the landslide before the earthquake was evaluated. Secondly, the dynamic failure process of the landslide under the measured ground motion was simulated with the discontinuous deformation analysis method. Lastly, based on stress–seepage coupling analysis and precipitation data from Ludian meteorological station, the stability of the landslide during subsequent rainfall after the earthquake was predicted. The results show that the critical seismic intensity was within degrees VIII–IX, which is consistent with the results of the earthquake damage investigation. The dynamic failure process can be divided into four stages, and four scarps formed; the potential sliding zones during the subsequent rainfall were at the first scarp and the fourth scarp, and their critical rainfall amounts were 35–40 mm and 55–60 mm, respectively. In this paper, failure process simulation and stability prediction of the landslide before, during, and after the strong earthquake are presented, which provide analysis methods for the dynamic stability of landslides in the meizoseismal area. [ABSTRACT FROM AUTHOR]

Earthquakes are a major landslide trigger, and evaluation of the dynamic stability of landslides under seismic action is very important. The Yanyangcun landslide, which is located at route marker K92 of the Xianggelila to Lijiang expressway in Yunnan Province, China, was chosen as a case study. Using the three-dimensional finite difference method and the unbalanced thrust method, three mechanical indices of the sliding zone, including the volume ratio of the elastic or plastic elements, the permanent displacement, and the residual thrusts of the slices, were calculated to evaluate the progressive failure and dynamic stability of the landslide when exposed to different intensities of seismicity. The safety factor of the landslide with reinforcement measures was also assessed. The critical peak seismic acceleration was about 2.29 m/s2, between earthquake intensity of VIII degree and IX degree. The landslide experienced progressive failure by means of shear at the leading edge, tension at the trailing edge, and immobilization of the middle part. The middle part of the sliding zone underwent a "locking effect," which could effectively resist the immobilization of the plastic zones of the leading edge and the trailing edge. With reinforcement measures, the dynamic stability of the landslide under VIII degree and IX degree events satisfied the allowable safety factor of the local specifications. The results provide guidance for disaster prevention and aseismic design for the Yanyangcun landslide, and can also be used as reference information for dynamic stability evaluation of other landslides threatened by earthquakes. [ABSTRACT FROM AUTHOR]