Debris flows were classified into one-phase and two-phase flows according to their movement features and the size distributions of solid particles.The intermittent feature of two-phase debris flows was studied with the natural and physical model experiments.The surge character in the experiments of the two-phase debris flow was obvious, and the head of the debris flow moved intermittently.In the experiment water flow initiated sediment from bed and side slopes and transported gravel particles to the front,accumulation of the gravel in the front of the flow made the height and front slop of the debris flow increase.Suddenly,the gravel moved forward as the slop reaches the critical value.Then the head height and slope reduced to some value and the flow stag again.The sediment supplied from upstream and energy accumulation caused the debris flow moving again. Based on the two-phase debris flow experiments,the formation and development of intermittent surges process was studied and the mechanical model was established.
