There are a vast number of large-scale ancient landslides in the east Tibetan plateau. However, these landslides have experienced reactivation in recent years and resulted in increasingly serious casualties and economic losses. To study the reactivation mechanism and early identification of ancient landslides on the eastern margin of the Tibetan Plateau, high-resolution remote-sensing interpretation, field survey, interferometric synthetic aperture radar (InSAR) monitoring, laboratory and in situ geotechnical tests, physical modeling tests, and numerical simulations were used, and the main results obtained are as follows. The development and distribution of ancient landslides on the eastern margin of the Tibetan Plateau were clarified, and an efficient identification method was proposed. Reactivation characteristics, triggering factors, and typical genesis patterns were analyzed. Second, the macroscopic mechanical properties of gravelly slip-zone soil and their strength evolution mechanisms at the mesoscale were revealed, and then the strength criterion of gravelly slip-zone soil is improved. Third, combined with typical cases, the reactivation mechanism of ancient landslides under different conditions is simulated and analyzed, and a multistage dynamic evolution model for the reactivation of ancient landslides is established by considering key factors such as geomorphic evolution, coupled endogenic and exogenic geological processes. Finally, an early identification method for ancient landslide reactivation was proposed, enabling rapid determination of the evolutionary stage of ancient landslide reactivation. These findings provide new theoretical and technical support for effectively preventing the risk of reactivation disasters of ancient landslides on the Tibetan Plateau.

Landslides induced by reservoir inundation are common in Southwest China, negatively influencing hydropower stations. The Wunonglong hydropower station dam was constructed in the upper reaches of the Lancang River, accordingly causing the water level at the Lajinshengu slope to increase by 30 m. A tension crack with a visible depth of 8 m was observed in the upper sector of the Lajinshengu slope after reservoir impoundment for 170 d. In the following days, numerous cracks appeared on the surface of the slope, and the maximum displacement of the slope reached 3.22 m. Then, a large-scale active deformation body within the Lajinshengu slope formed with an area of 2.62 x 105 m2 and a volume of 1.65 x 107 m3. Detailed field investigations, on-site monitoring, and centrifugal model tests were carried out to analyze the surface features, deformation characteristics, and failure mechanism of the Lajinshengu slope. The results show that the slope is an ancient landslide, divided into two parts (i.e. zone A and zone B) by the gully. Zone B is a traction landslide caused by the displacement of zone A. The longterm inundation weakens the soft rock at the slope foot, intensifying the toppling of bedrock and consequently triggering the sliding of the overburden in zone A. The failure mode of the Lajinshengu slope is a typical case of toppling-sliding failure, and the underlying rock toppling drives the overlying sliding. In addition, early identification methods for toppling deformation covered by overburdened soil were proposed based on monitoring data and deformation signs. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).