Two-Fraction Formulation of Critical Shear Stresses for Sand and Silt Mixtures
Two-Fraction Formulation of Critical Shear Stresses for Sand and Silt Mixtures
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DOI：
10.1061/(asce)0733-950x(2007)133:3(238
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发表时间：
2007-05
期刊：
影响因子：
--
通讯作者：
P. Dong
中科院分区：
文献类型：
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作者：
P. Dong
大多数河流和河口的河床沉积物通常是由粉砂和粘土颗粒形成的砂和泥的混合物组成。过去对泥浆的研究主要集中在由于粘土颗粒的存在而导致的泥浆的内聚特性上。只有有限的注意已经给了砂和非粘性粉砂颗粒的混合物的侵蚀行为。虽然大量的实验表明，在主要砂床中的泥沙颗粒的存在导致砂分数的临界剪切应力的增加，负责这种变化的机制尚不清楚，没有通用的公式可用于预测。本文提出了一个简单的两组分公式，用于确定无粘性砂-粉土混合物中砂组分的相对临界剪应力。该公式与泥沙的存在引起床面粗糙度变化，并相应减小作用在砂粒上的剪应力的机理基本一致。计算的相对临界剪切应力的砂部分在不同的粉砂含量和平均粉砂粒径显示出良好的协议与现有的实验数据。
The bed sediments in most rivers and estuaries usually consist of mixtures of sand and mud formed by silt and clay particles. Past studies of mud have focused mainly on the cohesive properties of the mud due to the presence of clay particles. Only limited attention has been given to the erosion behavior of mixtures of sand and noncohesive silt particles. Although a number of experiments have shown that the presence of silt particles in predominantly sand bed results in an increase in the critical shear stress of sand fraction, the mechanism responsible for this change is not clear and no general formula is available for prediction. In this note a simple two-fraction formulation is presented for determining the relative critical shear stress of sand fraction in a noncohesive sand-silt mixture. The formulation is broadly consistent with the mechanism that the presence of silt causes the changes in bed roughness with corresponding reduction of shear stress exerted on the sand particles. The calculated relative critical shear stresses for the sand fraction at varying silt contents and the mean silt particle sizes show good agreement with the available experimental data.