Potential failure patterns of a large landslide complex in the Three Gorges Reservoir area

Potential catastrophic re-activations of ancient massive landslides in reservoir areas have posed serious threats to the safety of local people and the ecological environment. Failure mechanisms and subsequent sliding processes of re-activated massive landslide complexes are relatively complicated and remain to be an open issue. In this paper, the potential sliding process of the Huangtupo landslide, one of the largest ancient landslide complexes undergoing multiple stages of motion in the Three Gorges Reservoir area, is numerically investigated by the arbitrary Lagrangian-Eulerian method with an adaptive meshing technique. The shear strengths of the soils in the sliding zone are determined using the strength reduction method along with a series of laboratory experiment tests. Sensitivity analysis is performed to examine the dependence of the sliding masses upon the shear strength, which illuminates the failure modes of the sliding masses under the weakening effect of water flow upon the toes of the landslide. Then, the sliding mechanisms and the influence zones of the landslides are analysed. Results show that the failure of a retrogressive landslide is much more harmful than that of a thrust-type landslide in the multi-stage landslide events and the consequence of a landslide is more severe when the sliding masses share common sliding surfaces. The present study provides a paradigm for the assessment of the consequence of massive landslide complexes from a numerical perspective.