Cohesive Soil Scour at Bridge Abutments: A Physical and Numerical Study

Accurate prediction of the scour depth and pattern is essential for safe and economic design of the bridge foundation. The local flow field around bridge abutments is a complex phenomenon. Most of the available studies focused on estimating the maximum or the equilibrium scour depth in non-cohesive sandy soil. Until recently, few investigations are available to estimate the equilibrium scour at bridge abutments in cohesive soil. The present study has two main goals. The first is to study the flow field around a vertical bridge abutment for sandy soil and clayey soil. The second is to develop scour prediction formulas to predict scour pattern at a vertical bridge abutment for sandy soils and for clayey soils. The study also aims to investigate the difference between the scour pattern for sandy soils and that for clayey soils. A computer program is developed to get the equilibrium scour pattern around the bridge abutment and the development of scour depth with time. The flow field around bridge abutment with all its features is investigated through detailed 3-D velocity measurements.