Critical shear stress and erosion of cohesive soils

This research is an analytical and experimental study of critical shear stress and erosion of cohesive soils. A model is developed for critical shear stress for erosion of cohesive soils based on application of a force balance on a particle or on an aggregate at the condition of incipient transport. A model is also developed for erosion of pure cohesive soils based on the rate of separation of aggregates during the turbulent bursting period. A model is developed for critical shear stress for erosion of pure cohesive soils, a model is developed for critical shear stress of mixed cohesive/non-cohesive soils with low clay content, and a model is developed for critical shear stress of mixed cohesive/non-cohesive soils with high clay content.; A flume apparatus was designed and constructed to perform experiments on critical shear stress and erosion of cohesive soils. Critical shear stress was measured for a pure clay mineral (kaolinite) and a natural soil (Buffalo River mud) with different consolidation times. Experiments were performed for mixtures of kaolinite and sand with various clay contents, for a consolidation time of 48 hours, for soil depths from 0.25 to 2.5 cm (0.1 to 1.0 inches). Experiments were also performed for erosion of cohesive soils, using Buffalo River mud, at consolidation times from 28 to 50 hours.; Applications of the models are analyzed with data from the present as well as data from a number of experiments from the literature. The results show that the models for critical shear stress for erosion can predict critical shear stress for various types of soils, with different bulk densities, consolidation times, and clay contents. The application of the erosion model to experimental data shows that the model can predict the erosion rates for various bulk densities, bed shear stresses, and consolidation times.