On the Stability of Deep‐Seated Landslides. The Cases of Vaiont (Italy) and Shuping (Three Gorges Dam, China)

Abstract

AbstractDeep‐seated landslides can have catastrophic impacts on human life and infrastructure when they suddenly fail. These events are devastating because of the large volumes of soil and rock masses involved and their often long runout. The present study suggests an energy‐based method to determine when a landslide becomes unstable, giving critical values for measurable variables (velocity and basal temperature) up to which remediation actions can be deployed. This work focuses on large ancient landslides reactivated by dam‐related water table variations that modify landslide stability. The main hypothesis of this work is that most of the deformation of deep‐seated landslides is concentrated on a thin, basal shear band forming the sliding surface. In particular, this assumption allows an approximation of deep‐seated landslides as elastic/rigid blocks sliding over a viscoplastic shear band, featuring weak phases like expansive clays. When the landslide moves, it causes friction in the shear band that raises the temperature of the clays until they become unstable and collapse catastrophically through a thermal runaway instability. The model is applied to the Vaiont landslide in Northern Italy and the Shuping landslide next to the Three Gorges Dam in China. The results of the model reproduce the sliding behavior of both landslides and provide constraints on the critical points of stability.