在泥沙起动的希尔兹曲线基础上，讨论比较了类同的各家试验曲线变化的共同点。即最容易冲刷起动的泥沙粒径为0.1～0.2 mm；再粗或再细，其起动流速渐升。同时，从实用观点考虑，找出了希尔兹曲线和类同试验曲线的经验公式。这些曲线公式，在细颗粒方面，若与用粘聚力或抗剪强度表征的粘性土转换为等效颗粒的公式比较，起动流速的计算结果尚称一致。在粗颗粒方面与一般的起动流速测验资料和公式比较，误差较大，而且颗粒愈大，偏大误差愈大。最后还提供了非正规水流的不同流态情况下寻求河床质起动流速的方法，并作为一例给出了底流式流态情况下防冲块石的起动流速公式。

Based on the Shields diagram of sediment incipient motion the similar experimental curves given by different scholars are discussed with comparison. The common characteristics of these curves are existing the easiest scour grain diameter of 0.1～0.2 mm and that the grain smaller or greater than this diameter the threshold velocity increased. Then by practical view the empirical formulas of Shields diagram and the similar experimental curve are found out. By comparison of the fine grain （<0.1～0.2mm）formulas of these experimental curves the formula of cohesive soil which the cohesion or shear stress are converted to equivalent grain diameter shows that the calculating results of threshold velocity are conformity each other. But by comparison of the coarse grain（>0.1～0.2）formulas of these curves with the general formula and practical data the discrepancy becomes large. And yet the larger the grain size the inclined large error increased. Finally the method to find the threshold velocity of bed material under abnormal flow pattern is suggested and the formula of threshold velocity under bottom flow pattern for scour defense of riprap stone is given as an example.