A set of solutions to the cohesive soil erosion problem were developed through this study.
A first device, the Erosionometer, was developed to perform a quick and reliable test to determine the critical shear stress of soils. The Erosionometer is based on physical shearing of the soil surface and has been calibrated through comparison with piston flume measurements of critical shear stress for entrainment of various fluvial bed sediments. This device is portable, easy to deploy in the field and in the laboratory and allows engineers and researchers to cover a sizeable terrain by performing many tests in a short timeframe, with immediate results. A modification to the Erosionometer was made to allow for subjecting the soil sample to a pressure differential while testing for critical shear stress. The added functionality is intended for investigating the effect of pressure gradient on the erodibility of cohesive soils by allowing for the erosion test to be conducted under a high pressure head while the other face of the sample (away from the flow) is maintained at zero head. Testing demonstrated that a positive pressure gradient on the eroding side (high pressure on flow side) can significantly increase the critical shear stress of cohesive soils, which is in line with other research available in the literature. The results show a simple linear relation between pressure differential and critical shear stress. Practical implications of these results are discussed.
A second device, the Erosion Rate Meter, or ERM, was developed to test cohesive soil samples to determine the rate of erosion under various levels of bed shear stress. This device, while being portable and fast to setup and run, is a very realistic simulation of the flow-bed interaction and allows for a direct measurement of bed shear stress on the soil sample and a precise measurement of the erosion rate. An obvious outcome of using the ERM is the easy development of erosion rate vs. bed shear stress relationships or models to characterize the different soils for design projects or further research. Of the 16 tested cohesive soils, all but two demonstrated a linear relation between erosion rate and bed shear stress.
The testing systems and methods developed in this research provide a comprehensive solution to the erodibility of cohesive soils from investigation to design. Significant improvements are achieved over existing systems in the speed, reliability, accuracy, and cost of estimating the erodibility of cohesive soils.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/39673 |
| Date | 30 September 2019 |
| Creators | Salem, Hicham |
| Contributors | Rennie, Colin |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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