非均匀沙分组起动规律的研究

本文在分析了非均匀沙起动情况后，采用输沙率法和分组相对输沙率法判别非均匀沙起动如果用其平均粒径d。来表示非均匀沙，则起动切应力和相同粒径的均匀沙近似，分组起动情况小颗粒由于受大颗粒的隐蔽作用鞍同等粒径的均匀沙需要较强的水流条件．相反大颗粒由于受暴露的影响比相同粒径的均匀沙容易起动．各粒径组的起动切应力可用公式(11)求出，

Research on law of grouping incipient motion of non uniform sediment

After analysing the incipient motion of non uniform sediment, the paper adopted both methods of sediment flux and of grouping relative sediment flux to discriminate it. If the mean grain diameter d m is used as equivalent diameter, the critical shear stress of non uniform sediment will approximately equal that of uniform sediment of the same grain diameter. Under grouping threshold conditions, the fines in non uniform sediment need more strong discharge condition than those of the same size in uniform sediment because they are hidden by the bulky grains. On the contrary, such condition will be reversed regarding to the bulky grains because of exposure effect. The critical shear stress of each grounp of particles can be calculated by formula 11.