Laboratory Measurements of Bed Shear Stress in Open Channel Flow and Soil Erosion Rate in Cohesive Soils
Thesis - Open Access
Master of Science (MS)
Department / School
Civil and Environmental Engineering
The relationship between soil erosion rate and bed shear stress is an important problem in sediment transport and scour. However, reliable measurements of the soil erosion function are challenging, both in the field and in the laboratory. The objective of this study is to investigate an experimental setup for conducting bed shear stress and soil erosion rate measurements using an open channel flume with a rough bed. These experiments were performed in an A-8 Hydraulic Channel with a fixed gravel bed. The flow discharge was kept constant at 0.158 ft.3/s, and bed shear stress was varied by changing the channel slope. A soil specimen was placed in a circular cutout in the gravel bed. Soil samples with a range of unconfined compressive strengths were prepared by changing the water content. The soil erosion rate was found from the difference in the mass of the sample before and after the test. Two different methods were used to estimate bed shear stress: from the measured velocity profile using the logarithmic law, and from the measured flow depth and channel slope. The velocity profiles were measured using the Particle Image Velocimetry (PIV) technique. The measured data showed that the equivalent grain roughness correlated well with the size of the large grains in the gravel bed. The equivalent grain roughness decreased with the flow-depth-to-grain-diameter ratios (h/d90). The bed shear stress in the sediment recess was not significantly different from the bed shear stress on the surrounding gravel bed. It was also found that the measured soil erosion rate correlated well with the unconfined compressive strength or water content.
Library of Congress Subject Headings
Shear strength of soils -- Testing.
Soil erosion -- Testing.
Number of Pages
South Dakota State University
Kern, Gunnar Schurmann, "Laboratory Measurements of Bed Shear Stress in Open Channel Flow and Soil Erosion Rate in Cohesive Soils" (2021). Electronic Theses and Dissertations. 5772.
Environmental Engineering Commons, Hydraulic Engineering Commons, Water Resource Management Commons