土石流の慣性領域での流動則

Abstract

New theories which consider more precisely the structures of the stony, the hybrid and the muddy type debris flows than ever presented models are introduced. If the solids concentration near the bed exceeds a threshold value larger than that the particles are always in touch with others while in motion, the static pressure and friction acting directly between particles are not negligible and the particles within this layer are sustained by both the static Coulomb friction force and the dynamic repulsion force.Whereas, in the upper part of the flow where the solids concentration is less than the threshold value, no static stress is operating and if particles are coarse they are sustained by only the dynamic repulsion force. This is the case of the stony type debris flow. If the composing particles are fine but noncohesive, they can be suspended in the upper layer by the effect of macro-turbulence. This kind of flow is called the hybrid flow. Especially of the hybrid debris flows that the highly concentrated lower layer is limitted in a narrow boundary on the bed is called the muddy type debris flow.The stress balance equations for each type flow are numerically solved and the concentration and velocity distributions in each type flow are obtained. The new theories explain the experimental results as well as hitherto simpler Takahashi's theories.