Numerical Simulation of Initiation of Rainfall-Induced Debris Flow

Two-phase flow model, modified Mohr-Coulomb model and the theory of unsaturated soil are adopt in FLAC, and then the characteristics of seepage flow of Beichuan soil under rainfall conditions are numerically simulated. It is shown that the initiation of rainfall-induced debris flow is affected by rainfall density and duration. The maximum horizontal displacement occurs at the foot of the slope and increases with rainfall duration. The vertical displacement is non-uniform and the maximum value occurs at point A, which is at the top of two-third. Whether or not a sudden change of displacement occurs at the characteristic point A is suggested to judge if debris flow starts. It is also shown there is a good agreement between numerical simulation results and rainfall model test data in laboratory.