Numerical investigations of the failure mechanism of spreading landslides

Abstract

Spreading landslides are geohazards that often occur in sensitive clay areas. A unique characteristic of the spreads is that an initial small local slope failure may cause a catastrophic landslide above the horizontal failure surface, forming horsts and grabens. Although many hypotheses were proposed to explain the failure mechanism of spreads, some topography of the landslides observed from field investigations cannot be well explained by the existing hypotheses. This study revisits the 2010 Saint-Jude spreading landslide by using the coupled Eulerian–Lagrangian approach within ABAQUS to reveal the failure mechanism of spreading landslides. Two types of cross-sections (static and dynamic cross-sections) were selected to monitor the total horizontal force of the sliding mass during the process of migration. It was found that there are two spreading failure mechanisms to form horsts and grabens. The first one is the static spread failure mechanism that global failure occurs accompanied by spreading failure. The other one is the dynamic spreading failure mechanism that after the global failure, the sliding masses break into horsts and grabens during the forward movement under the pushing of the sliding mass at the back and the blocking action of the soil mass in the front. These two failure mechanisms of spreads can well explain various geomorphologic shapes found in the Saint-Jude landslide.