泥石流是发生在沟谷和坡地上的饱含小至粘土、大至巨砾的固液两相流,液相是水和细颗粒泥沙掺混而成的均质浆液,固相是较粗的颗粒。这里所谓细颗粒泥沙在容重较小时指的是粉沙及粘土,在容重大时则包括沙在内。

The motion of debris flows can be depicted in the following manner:1. Debris flows consist of the neunrally suspended load, the suspended load and the bed load. The fine particles (silt and clay in general and including sand for debris flows with heavy concentration), called as "neutrally suspended load" in this article, mix thoroughly with water and form the liquid phase-------the slurry which behaves as a Binghamfluid. The coarse particles in turbulent debris flows move as suspended load and bed load, and assume the form of bed load in quasi-viscous and viscous debris flows. Both the suspended load and the bed load form the solid phase of the flow.