Relationship between Cohesive Soil Erosion Behavior and the Physical and Geochemical Properties of Soil in Tennessee, USA

Erosion properties of cohesive soils can be defined with respect to excess shear stress and are dependent on two fundamental properties of soil: a threshold critical shear stress and erodibility coefficient. However, the prediction of cohesive soil erodibility is challenging in that limited advancements have occurred in developing an improved prediction model, especially compared to granular non-cohesive sediments. The inter-particle attraction in cohesive soils is one main reason behind this difficulty since the particle-level interactions are influenced by physical, geochemical and biological properties. In different geological locations, these properties vary spatially along both the stream bank and bed. No empirical approach has been published to date in which the engineering community has significant confidence with its predictability. This study was conducted in a geologically diverse region in the United Sates in order to improve the understanding of cohesive soil erosion processes. Field data were collected using the mini-jet tester from 21 streams in four geological regions of Tennessee. Soil samples were collected from the jet testing locations for laboratory measurement of physical and geochemical properties. Jet-tester field data were analyzed using the Blaisdell (1981) approach for estimating the critical shear stress (τ_c) and erodibility coefficient (k_d) of the cohesive soils. Finally, multivariate statistical approaches were applied on these data for developing a predictive relationship of cohesive soil erodibility based on significant soil properties. Relationships among different geological regions were analyzed as well. Findings from this research identified key soil properties strongly correlated to τ_c and k_d parameters.