Ejection landslides triggered by the 2008 Wenchuan earthquake and movement modelling using aerodynamic theory and artificial disintegration collision technique

Many ejection landslides in the 2008 Wenchuan earthquake exhibited unusually dramatic behaviour in which a huge sliding mass was launched into the air and supported for a long distance because of the aerodynamic effect. In this paper, the formation conditions and movement characteristics of ejection landslides are analysed. The flight behaviour of the centroid of the ejection mass is studied by numerical solution with and without the aerodynamic effect. The impact and movement processes of the sliding mass are simulated by incorporating an advanced discretisation approach into discontinuous deformation analysis (DDA). Simulation results of the Dayanke rock avalanche induced by the 2008 Wenchuan earthquake show that the aerodynamic effect significantly affects its flight behaviour before collision. Simultaneously, the colluvium on the slope surface remarkably reduces its traveling speed and runout. Moreover, the initial angle between the velocity of the detached ejection mass and the horizontal direction strongly affects the flight distance and final deposition pattern of the avalanche.