Temporal variation of clear-water scour at compound Abutments

Most of actual abutments in rivers are built on foundation, while there is limited number of study available on the effects of the foundation on the local scour. In this study, temporal variation of local scour around compound abutment was investigated experimentally under clear-water conditions. The results showed that a suitable level of foundation is able to decrease the scour depth and increase scour time during the flood events. The trend of temporal scour depth at compound pier and abutment is similar. The scour depth develops to top of foundation quickly, and then the foundation postpones the scour development (lag-time). Duration of lag-time depends on the foundation level, velocity ratio (U/Uc) and foundation dimension. This study highlights that proper design of foundation level increases duration of scouring and provides enough time to treat bridge foundation after the flood events.