An experimental study on the effects of physical, mechanical, and electrochemical properties of natural cohesive soils on critical shear stress and erosion rate

The field of cohesive sediment erosion is still not fully understood, in large part due to the many soil parameters that affect cohesive sediment erodibility. In this study several undisturbed natural soil samples were taken from different river banks in Manitoba, Canada. The samples mainly contained clay and silt with 24–94% clay content, thus the study covered a wide range of cohesive soil. For each sample 13 different physical, mechanical, and electrochemical properties were measured. Critical shear stress of erosion and erosion rate were quantified using an Erosion Measurement Device (EMD). Stepwise regression was used to find the variables most significantly correlated to critical shear stress and erosion rate, which led to the development of a new empirical equation to estimate the critical shear stress of cohesive soils. It was found that the critical shear stress is highly correlated with cohesion, while both cohesion and sodium adsorption ratio (SAR) had significant influence on the erosion rate.