Run-out Analysis of Debris Flow by Using MPM and Depth Averaged Equation

Abstract

In recent years, it is important to evaluate the debris flow risk with help of run-out analysis, instead of prevention by a control dam as the provision against damage from debris flows. In this study, the result of run-out analysis of debris flows by the practical depth averaged method by using Material Point Method (MPM) is presented in order to help debris flow risk zoning. According to the analysis method suggested in this study, we can simulate the behavior of debris flow by using constitutive law in soil mechanics, namely Drucker-Prager model, with geotechnical parameters, including the aspect of fluid behavior. In addition, this method enables us to do run-out analysis of debris flow in a vast area where an actual debris flow will spread with small calculation cost. In this paper, the outline of MPM and the depth averaged method discretized by MPM (DAMPM) is introduced. Then, the result of simulation of debris flow in the vast area which includes an actual river with a high danger of mud and debris flow is presented. As the result, we could quantitatively calculate the amplitude of velocity, depth and basal force which are brought by the debris flow at a specific point.