Cohesive soils generally include fine-grained silt and clay mineral particles passing the No. 200 sieve. These particles usually have a shape of small flat plates, needles, or tubes with high specific area defined as the ratio of surface area to volume in the presence of water. These particles are subjected to physicochemical forces that are large in comparison with their weight, which tends the soil mass together. These physicochemical forces are more dominant than the submerged particle weight in resisting erosion. However, attempting to apply an understanding of the physicochemical forces on the micro level is challenging and may not yield practical results because erosion of cohesive soils generally occurs at the more macro scale of clumps of soil rather than individual particles. The course material is based on FHWA Publication Number FHWA-HRT-15-033: Scour in Cohesive Soils.

At the conclusion of this course, the learner will have a better understanding about the Physical and Chemical Properties of Cohesive Soils and Influencing Factors as well as an understanding of the following topics:

• Cohesive soil and its physical and chemical properties
• The influence of various parameters that cause soil erosion
• Various models and testing conditions of scour depth
• Field testing procedures of soil erosion