NUMERICAL STUDY ON A DEVELOPMENT PROCESS OF DEBRIS FLOW BY THE ENTRAINMENT OF BED MATERIAL IN TORRENT SEDIMENT LAYER

Abstract

Moving liquefied soil block caused by a small landslide sometimes runs out to mountain streams over the erodible bed layer. Then, the debris flow arises and has been developed by the entrainment of bed materials into the flow body. In this study, we focus such a process by using the proposed numerical simulation, which is composed of the particle-fluid multiphase flow analysis by using the Distinct Element Method coupled with the unsteady 1D flow calculation. Numerical results show the complicated time-depended process of the entrainment of debris material into the flow body and the increasing sediment discharge of debris flow according to the supplied water volume at upper boundary condition.