Evaluation technique for erosion rate of cohesive sediment and its application to the geomorphological

对粘性泥沙的冲刷过程进行了试验研究。已经在实验水槽中进行了基础研究，以评估均匀粘性沉积物的侵蚀率。本文研制了一种可移动的泥沙冲刷试验装置，对天然粘性泥沙的冲刷速率进行了现场测试。我们还建立了这种测量的实验技术。为了验证该装置的有效性和实用性，在大型露天实验水槽中进行了一系列的测量。经验证，其结果与本实验室标准试验的准确度基本相当。本文还研究了泥沙粘聚力对裸坡侵蚀过程的影响。这是本研究的第二部分。通过人工降雨试验，研究了粘性泥沙组成的模型裸坡在人工降雨作用下的地貌变化。在此之前，我们所做的粘性泥沙冲刷试验技术的资料是有指导意义的。在这一系列试验中，粘土含量比只是需要改变的参数。结果表明，随着粘粒含量的增加，在坡面上形成的主河道变窄、变深。床面垂直侵蚀比侧滩侵蚀占主导地位。研究还表明，粘性裸坡的侵蚀过程和沟道网络的几何形状与无粘性裸坡有着不同的特征。

Erosion process of cohesive sediment was investigated experimentally in this study. Fundamental studies had been already conducted in the experimental flume to evaluate the erosion rate of uniform cohesive sediment. In this study, we developed a movable apparatus of erosion test, which was designed to conduct a field measurement of erosion rate of naturally deposited cohesive sediment. We also established the experimental techniques for such a measurement. Several series of measurements were conducted in large-scale open-air experimental flume in order to check the validity and utility of this apparatus. It was verified that the results had almost same order of accuracy as that by our standard test in laboratory. This is one of the main achievements of this study.The effect of cohesiveness of sediment on the erosion process of bare-slope was also investigated here. This is the second part of this study. Experiments were conducted to investigate the geomorphological change in model bare slope, which was constituted by cohesive sediment, due to an artificial rainfall. Before doing that, the information about the experimental technique of erosion test of cohesive sediment by us was instructive. Clay content ratio is only the parameter to be changed in this series of experiments. It was seen that the main channel which formed on the slope grew narrower and deeper as the clay content ratio increased. Vertical erosion on the bed was found to be more dominant than the lateral bank erosion. It was also understood that the erosion process and the geometry of channel network in case of cohesive bare slope have different characteristics than those of cohesionless slope.