本文分析了宾汉流体中宾汉极限剪切力τB 对泥沙起动起阻碍作用的力学机制 ,得出均匀无粘性沙的起动拖曳力的一般表达式 .并对结果定性分析得到 :(1)存在粒径D ,对粒径小于 0 1D 的泥沙 ,起动中重力因素可忽略不计 ;对粒径大于 10D 的泥沙 ,宾汉极限剪切力因素可忽略不计 .(2 )宾汉流体中τc 随颗粒粒径D的变化关系为马鞍状曲线 .存在某个粒径Dmin,其所需τc 最小 . In this paper, the mechanics mechanism of the Bingham limit shear force τB on Bingham fluid impeding the sediment onset is analyzed, and the general expression of drag coefficient of uniform viscous sand is obtained. The qualitative analysis shows that: (1) The existence of particle size D, for the particle size of less than 0 1D of sediment, the starting gravity factor is negligible; particle size greater than 10D of sediment, Bingham limit shear force negligible factors. (2) Bingham fluid The variation of τc with the particle size D is a saddle-like curve, with the smallest required τc for a particle size Dmin.