ANALYSIS ON CRITICAL HYDRAULIC CONDITION FOR STARTING MOTION OF LARGE-SIZED PARTICLES IN VISCOUS DEBRIS FLOW

Debris flow is a devastating geological disaster due to the destructive power of large-sized particles. The large-sized particles have greater power than the liquid at the same volume and velocity. In order to investigate the starting mechanism of large-sized particles in viscous debris flow, a reasonable and simple calculation model is developed. The flow condition is the key factor of the debris flow outburst. Considering the random distribution of relative position between supporting and starting particles, the critical hydraulic condition of upstream is achieved by analyzing the particle forces under the impact of slurry. The forces include the lift force, drag force, effective gravity. The particles' moment equilibrium equation of staring condition is solved. The proposed formula of critical starting velocity is consistent with universal laws. The theoretical results by proposed formula are in good agreement with numerical simulation results of three typical cases made by CFD software FLUENT. The proposed formula has significance for preventing and controlling debris flow, especially in the calculation of the discharge in separation of water and solid.