Assessing scour and erosion resistance in fine-grained soils

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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.