Reactivation characteristics and dynamic hazard prediction of an ancient landslide in the east margin of Tibetan Plateau

The increasing human engineering activities and frequent extreme weather events have caused extensive reactivation of ancient landslides, which are widely developed in the east margin of Tibetan Plateau. The Shangyaogou landslide, as a typical ancient landslide example in this area, was investigated to reveal the reactivation characteristics, and its stability was calculated under the continuous rainfall condition with the intensity 30 mm/day using the finite element software Geo-Studio. The whole movement process and hazard prediction under the different triggering conditions were simulated using the numerical software DAN3D. The study results showed that: (1) under the joint influence of Mw 7.9 Wenchuan earthquake, toe erosion and intensive rainfall, multi-stage deformations occurred to the front part of the Shangyaogou landslide in multiple periods and also indicated a significant potential instability; (2) under the continuous rainfall condition, when the single effective total infiltration reached about 65 mm, the reactivation part will become unstable. While the single effective total infiltration reached about 120 mm, both reactivation part and posterior part became instability; (3) the maximum run-out distance of the reactivation part was calculated to be 350 m, and the forefront of the accumulation deposit would not reach the residential area; When both parts failed simultaneously, the maximum run-out distance was calculated to be 550 m by considering the thickness and dynamic energy of the accumulation deposits, and the vulnerable elements inside the fan area with radius of 150 m would be severely threatened; (4) abundant earthquake-triggered landslides have been developing in history or in recent years in the eastern margin of Tibetan Plateau. Some of them have been partly reactivated due to the increasing human engineering activities and extreme rainfall events, and they have a potential for further deformation and failure. The presented study methods can provide guidance for local disaster prevention and mitigation, and can be used as a reference for the hazard prediction of the similar ancient landslides which have been reactivated.