Erosion of mud/sand mixtures
Erosion of mud/sand mixtures
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DOI：
10.1016/s0378-3839(96)00002-6
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发表时间：
1996-12
影响因子：
4.4
通讯作者：
H. Mitchener;H. Torfs
中科院分区：
文献类型：
--
作者：
H. Mitchener;H. Torfs
泥沙冲淤预测是海岸工程建设中的一个重要问题。有方法预测粘性沉积物（泥）和非粘性沉积物（砂）的侵蚀，但目前没有混合沉积物的关系。然而，天然沉积物很少只由泥或砂组成，需要泥和砂沉积物组合的侵蚀特性，以便可以模拟天然沉积物粒度组合的整个范围。本文试图以一种可用于预测模型的方式来描述混合沉积物的侵蚀行为。本文将泥（或细粉）定义为通过62.5 μm筛的粘土和粉砂，并将砂定义为保留的部分。欧洲研究人员在MAST G8 M项目框架内的合作积累了大量关于泥/砂混合物侵蚀的数据。这些数据来自实验室和现场实验，已被用来研究泥/砂混合物侵蚀行为背后的物理过程。有人发现，添加砂泥，反之亦然，增加抗侵蚀性和降低侵蚀速率时，超过侵蚀的临界剪切应力。均匀混合床的侵蚀剪切应力的最大值出现在30至50%重量的砂的区域中的最大值。对抗侵蚀性的最显著的影响发生在向砂中添加按重量计小百分比的泥浆时。侵蚀模式也从无粘性变化到粘性行为，在低泥含量添加到砂中，过渡发生在3%至15%泥重量的区域。侵蚀特性也很大程度上取决于河床的历史，通常在典型的沉积条件下，由于泥砂在水中的沉降速度不同，泥砂会分离，从而形成离散层。因此，这些隔离层的侵蚀应模拟为一系列泥砂侵蚀“事件”。
The prediction of sediment erosion is an important issue in coastal engineering projects. There are methods for predicting the erosion of cohesive sediment (mud) and non-cohesive sediment (sand), but there are presently no relationships for mixed sediments. However, natural sediments rarely consist of only mud or sand and the erosional properties of combined mud and sand sediments are required so that the whole spectrum of natural sediment size combinations can be modelled. This paper attempts to characterise the erosion behaviour of mixed sediments in a way that can be used for predictive models. In this paper mud (or fines) is defined as clays and silts, which pass through a sieve of size 62.5 μm, and sand is defined as the fraction retained. The collaboration between European researchers in the framework of the MAST G8M project has resulted in the accumulation of an extensive amount of data on the erosion of mud/sand mixtures. The data, which originate from both laboratory and field experiments, has been used to examine the physical processes behind the erosion behaviour of mud/sand mixtures. It was found that adding sand to mud, or vice versa, increases the erosion resistance and reduces the erosion rates when the critical shear stress for erosion is exceeded. The highest values for the erosion shear stress of homogeneously mixed beds occurs at a maximum in the region 30 to 50% sand by weight. The most significant effect on erosion resistance occurs on the addition small percentages of mud by weight to sand. The mode of erosion also changes from cohesionless to cohesive behaviour at low mud contents added to sand, with a transition occurring in the region 3% to 15% mud by weight. The erosional properties are also strongly dependent on the history of the bed and it is common that mud and sand segregate under typical deposition conditions owing to their different settling velocities in water which creates discrete layers. The erosion of these segregated beds should thus be modelled as a sequence of mud and sand erosion “events”.