Determination of Rectangular Collar Dimensions for Reducing Scour Around Bridge Pier

Different methods have been proposed to prevent or reduce scouring around bridge piers. Making use of collars as countermeasures has recently been noticed by researchers. Collar dimensions have great impact on reducing local scour around bridge piers. This study showed that rectangular collars around circular piers reduced both intensity of scouring and depth of scour hole. In this study the effects of collar length in up and down-stream of the pier model and also on its width were investigated. The dimensionless length of rectangular collar in upstream (Lu/D) and downstream (Ld/D) found to be 0.92 and 1.42, respectively, and the width of collar was estimated 3 times greater than the pier diameter. It is noteworthy to mention that with these dimensions scouring process was rarely observed around the pier model after elapsing 62 hours.