Assessing scour and erosion resistance in fine-grained soils

建议的研究重点是开发评估细粒土壤抗冲刷和侵蚀能力的方法。冲刷评估是许多重大基础设施工程设计的重要内容。如果桥墩周围的冲刷破坏了桥墩的基础，桥梁可能会倒塌。灌溉渠道中的水坝、涵洞、堰和落差结构可能会因下游河床的冲刷而不稳定。这些结构的失效会造成巨大的经济损失，而且往往会对公共安全构成威胁。 本文所描述的工作分为三个研究。第一项研究将用于通过测量土壤可蚀性的通用技术更好地了解侵蚀的机理。学生将研究冲刷坑形状变化时水流在冲刷坑中的行为，以更好地预测土壤表面被侵蚀时的应力状况。学生还将尝试理解富含粘土的土壤如何受到侵蚀它的水流的压力波动的影响。这项工作将用于提高喷射侵蚀试验评价土壤抗侵蚀能力的准确性。对于第二个项目，将对三种类型的土壤抗侵蚀试验的结果进行比较。测量土壤抗侵蚀性能的仪器有很多，但比较不同仪器之间的结果的工作很少。这项工作将为工程师提供关于哪种设备可能提供最准确结果的建议。对于第三个项目，将对圆形墙喷流在细粒材料中形成的冲刷洞的时间发展进行实验，该冲刷洞模拟在涵洞下方形成的冲刷。其目的是开发一种方法来预测在冲刷过程中特定时间在涵洞下方可能产生的冲刷洞的大小，该方法将适用于粘性土壤和沙子。其目的是为工程师提供一种简单的方法来确定涵洞工地是否需要防侵蚀。

The proposed research focuses on the development of methods to assess scour and erosion resistance in fine-grained soils. Assessment of scour is important to the design many major infrastructure works. Bridges can fail if scour around bridge piers undermines the foundations of piers. Dams, culverts, weirs, and drop structures in irrigation canals can be destabilized by scour of the downstream riverbed. Failure of these structures represent significant economic loss and often a threat to public safety. The work described herein is divided into three studies. The first study will be used to better understand the mechanics of erosion in a common technique for measuring soil erodibility. A student will investigate how the flow behaves in a scour hole as the shape of the scour hole varies to better predict the stress conditions on the soil surface as it is eroded. The student will also attempt to understand how a clay-rich soil is affected by the pressure fluctuations of the flow eroding it. The work will be used to improved the accuracy of the jet erosion test for assessing soil erosion resistance. For the second project, results from three types of soil erosion resistance tests will be compared. There a multitude of devices to measure the erosion resistance of soils, but there has been little work to compare results between devices. The work will provide engineers advice on what device might be giving the most accurate results. For the third project, experiments will be conducted on the time development of the scour hole created by a circular wall jet in fine-grained material, which models the scour created below culverts. The aim is to develop a method to predict the size of the scour hole that might be generated below a culvert at particular time in the scouring process that would be applicable to both clayey soils and sands. The goal is to provide engineers with a simple method to determine whether erosion protection is required at a culvert site.