The consistency of laboratory jet erosion tests performed on undisturbed samples

The U.S. Army Engineer Research and Development Center performed 75 laboratory Jet Erosion Tests (JETs) on undisturbed samples collected from the riverbank along the Lower American River (LAR) near the city of Sacramento, California, to identify the erosion resistance of soil along the riverbanks and riverbed of the LAR through the erosion parameters of erodibility coefficient, Kd, and critical stress, τc. Thirty-nine of the samples were Shelby tube samples and the other forty-two were 4 in.-diameter Plexiglas tube samples. The soil type varied from weak sandy silt to stiff silt with the JET results varying from Very Erodible (VE) to Very Resistant (VR). For many of the samples, the variations in results were due to changes in the quality of the undisturbed samples; however, the variations may also be caused by the changes in the soil type from silt/sand to clay in some of the tested samples and natural variability of the soils. The method of sampling tube and the process of cutting the tube may also add to the variability in test results. To use the erosion parameters for specific soil types outside of the samples tested, the erosion parameters were related to index properties of the soil: particle diameter, percent clay content, and Plasticity Index. Erosion parameters were found to be most significant correlated to the particle diameter