COLLABORATIVE RESEARCH: Experimental Study of the Effect ofSediment Sorting on Bed Forms, Bed-Surface Texture and Fractional Transport Rates in Coarse, Mixed-Size Sediments

当单向电流通过粗粒度混合沉积物床时，会产生多种床型，并且在负荷、床面层和基材之间存在粒度分离。河床形态、搬运的泥沙和底物之间存在着强烈而复杂的相互依存关系。在实验室和野外对分选良好的沙子进行的许多研究，已经使人们对熟悉的沙丘床形式的行为以及床形式与运输之间的相互作用有了相当好的理解。最近，在分级差的砂砾混合物流中，出现了各种各样的特征，如床积层、砾石波和碎屑堵塞。这些看似不同的床层特征之间的关系，以及它们对床层尺寸分离的依赖，尚不清楚。这是一项关于单向流动中河床特征的性质的实验研究，它是流动强度和沉积物分选的函数，涉及几种平均尺寸约为4毫米但分选差异很大的沉积物混合物，并在每种沉积物混合物上以几种平均流速进行一系列运行。目的是对这些流动中产生的各种床层特征的基本特征和相互关系作出统一的描述。这项工作将与筑波大学环境研究中心的Hiroshi Ikeda教授、Shigemi Takayama教授和Fujiko isiseya博士合作完成。这项建议包括PI和研究生研究助理两年的工资和旅费。Peter R. Wilcock教授（约翰霍普金斯大学）正在提交一份具有相同科学内容的配套提案。这家日本公司已经有了建造实验设备和进行实验的资金。

When a unidirectional current passes over a bed of coarse mixed-size sediment, a variety of bed forms are generated, and there is segregation of particle sizes among the load, the bed surface layer, and the substrate. There is a strong and complex interdependence between the bed forms, the transported sediment, and the substrate. Many studies in well sorted sands, both in the laboratory and in the field, have led to fairly good understanding of the behavior of the familiar dune bed forms and the interaction between bed forms and transport. More recently, features variously described as bed-load sheets, gravel waves, and clast jams have been reported in flows over poorly sorted sand-gravel mixtures. The relationships among these seemingly diverse bed features, and their dependence on size segregation in the bed, is unclear. This is an experimental study of the nature of bed features in unidirectional flows as a function of flow strength and sediment sorting involving several sediment mixtures with the same mean size of about 4 mm but with widely varying sorting and making series of runs at several mean flow velocities over each sediment mixture. The objective is a unified picture of the fundamental characteristics and interrelationships of the various kinds of bed features produced in these flows. The work will be done in cooperation with Prof. Hiroshi Ikeda, Prof. Shigemi Takayama and Dr. Fujiko Iseya of the Environmental Research center at the University of Tsukuba. This proposal covers salary and travel for the PI and a Graduate Research Assistant for two years. A companion proposal with identical scientific text is being submitted by Prof. Peter R. Wilcock (The Johns Hopkins University). The Japanese group already has funds for building the experimental apparatus and conducting the experiments.