Formation mechanism and evolution of the Jiaju landslide in the Dadu River, China

The Jiaju landslide is a large soil-rock palaeolandslide in the Danba section of the Upper Dadu River in southwestern Sichuan Province, China. In this work, geological investigations, long-term comprehensive monitoring, experiments, and numerical simulations were used to determine the formation mechanism and evolution of this landslide. A complex armchair-shaped terrain with a substantial height difference between the rear and the foot of the slope, multiple structural defects within the landslide-accumulation region, and a coupling effect among multiple factors controlling river erosion and human activity were identified. The dynamic landslide deformation process was recorded by the integration of global positioning system (GPS) and inclinometer data, and the kinematic behaviour of the landslide was simulated using a Fast Lagrangian Analysis of Continua in 3 Dimensions (Flac3D) model in three stages. (1) During the last rapid uplift of the Tibetan Plateau and strong river erosion, the Jiaju bank slope was deformed and failed, forming a massive, thick palaeolandslide with a volume of approximately 2.76 x 107 m3. (2) The structure of the landslide materials deteriorated, and the weak structural plane was softened by groundwater and surface loading. The landslide was reactivated, with deformation and failure occurring through sliding and fracturing. (3) The landslide exhibited creep deformation with multistage and multilayer sliding surfaces via front-slope toe excavation and river-level fluctuations.