抄録
Governing equations for debris flow are composed of mass conservation equations for the flow body and bed sediment, and equation of motion. The erosion rate equation is usually added to close the governing equation system. The shear stress formula in equation of motion is derived based on uniform flow condition and has two terms; Coulomb shear stress and dynamic shear stress. In this equation set, sediment concentration of the flow is determined so that Coulomb shear stress accords with external force at the theoretical bed. Consequently, Coulomb shear stress, dynamic shear stress and sediment concentration correlate with each other. However, numerical, unreasonable disturbances take place because of the dependency of dynamic shear stress on Coulomb shear stress, when we apply this equation set to strongly unsteady debris flows. In order to solve these problems, we derived a new dynamic shear stress equation which doesn't depending on Coulomb shear stress. Numerical simulations of debris flow for erosion and deposition processes were performed. The results show that the behavior of the debris flow can be clearly explained.
