Experimental Study of Local Scour around a Vertical Pier in Cohesive Soils

Estimation of maximum scour depth is an important factor in designing structures that are embedded in rivers. Using a hydraulic model, the mechanism of local scour around bridge piers that are embedded in cohesive soils has been studied. Experiments were performed in a flume of 22m long, 0.77m wide and 0.60 m deep with a pier of 0.1 m in diameter. Also, three types of cohesive soils with different percent clay were used. While changing parameters, such as current velocity, flow depth, initial moisture content, clay percentage, and undrained shear strength in each experiment, the scour depths were measured.The measured data was adjusted by hyperbolic law. Using dimensional analysis, a relationship between the ultimate scour depth and effective parameters was developed. Finally, the ultimate scour depths obtained by experiments were compared with those calculated by empirical equations.