Erosional effects on runout of fast landslides, debris flows and avalanches: a numerical investigation

The mechanism of mass changes in debris transportation process is an important topic in the study of fast landslides, debris flows and avalanches. Basal erosion is recognised as a dynamic interaction between the original moving material and the entrained basal topsoil shearing along their non-slip contact surface. In this paper we propose a new concept of yield rate and establish the erosional relationship to bridge these two systems. A pertinent mathematical model and numerical implementation are formulated. Parametric numerical experiments are conducted to compare the erosional effects. The simulated results are consistent with available experimental and field observations. The influence of the involvement of the erosive material on runout behaviour and the global mobility of the moving material are elucidated. The proposed method is then employed to analyse a recent debris flow event in northern Italy. The excellent match to the field data gives it a plausible potential application to the analysis of this type of gravity-driven flow with significant erosion. Defined in a dimensionless form, the proposed field rate can be estimated conveniently in general geotechnical practices.