中文摘要：

Shields曲线常用于表示泥沙起动的临界条件，基于边界层理论，对Shields曲线各个流区的线型进行了推证；考虑粘结力的作用，对Shields参数及Shields曲线进行了修正，并给出修正Shields曲线表达式；在此基础之上，从边界层角度重新阐述了Shields曲线。结果表明：Shields曲线在光滑紊流及层流区呈直线分布，在过渡区与阻力系数线型保持一致，在粗糙紊流区呈水平直线分布；修正后Shields曲线与原始Shields曲线在形式上保持一致，修正Shields曲线表达式与实测数据吻合较好，适用于粗、细颗粒泥沙起动条件的计算；Shields曲线事实上代表了Shields参数与沙粒周围绕流流态的关系，同一颗粒处于不同流区起动时，其起动切应力不同。

英文摘要：

The Shields curve is often used to judge the criterion for incipient sediment motion. The curve for all the flow regimes is derived on the basis of the boundary layer theory. The Shields parameter and curve are modified in order to take into account the effect of viscosity. The modified curve is then re-explained from the viewpoint of boundary layer. Results show that the curve＇s shape exhibits a linear distribution in the smooth turbulent and laminar regime. In the transition regime, the curve is similar to that representing the friction law for steady flow, and finally becomes a horizontal curve in the rough turbulent regime. The modified Shields curve keeps the consistent shape with the original one. The modified curve is applicable to predict the incipient motion of both fine and coarse sediment particles. The prediction agrees well with measured data. In fact, the Shields curve represents the relationship between the threshold bed shear stress and the flow status around the particle. The threshold bed shear stress of one particle is different under different flow regime conditions.