Exoerimental study on erosion rate of cohesive sediment and the attempt toward direct measurement of it in revers.

本文研究了自然沉积在河床上的软粘性沉积物的侵蚀过程。进行了一系列广泛的实验，系统地设置了条件，以评估水流在封闭管道中的侵蚀率。测试样品由硅砂、粘土和水的混合物组成，其组成被设置为一个变量。控制这一过程的主要因素是粘土含量比（粘土与总沉积物的重量比）、含水量比（水与粘土的重量比）、流动的摩擦速度、水温、硅砂的大小和干湿历史。定量评价了这些参数对侵蚀速率的影响。根据试验结果，推导了侵蚀速率公式。并对这一过程的机理进行了探讨和一定程度的阐明。在这些基础研究的基础上，研制了实际河流侵蚀速率的便携式测量系统，并进行了一系列的测量，验证了该侵蚀试验的有效性。

The erosion process of soft cohesive sediments, which were deposited naturally on a river bed, is investigated in this study. Extensive series of experiments, conditions of which were set systematically, were conducted to evaluate the erosion rates by running water in a closed conduit. Test samples consisted of a mixture of silica sand, clay and water, the composition of which was set to be a variable. The main factors which govern this process were found be the clay content ratio (the weight ratio of clay to the total sediment), the water content ratio (the weight ratio of water to the clay), and a frictional velocity of flow, a water temperature, the size of silica sand and the dry-wet history. The effects of these parameters on the erosion rate were evaluated quantitatively. The erosion rate formula was also derived on the basis of experimental results. Also, the mechanism of this process was examined and made clear to a certain extent. In addition to these fundamental studies, the portable measuring system of erosion rate in a real river was developed, and a series of measurement was also conducted confirm the validity of this erosion test.