Effect of Collar Shape on the Local Scouring Around the Bridge Piers

Scouring around bridge piers causes serious damages to these structures all around the world every year. In order to control this phenomenon, riprap is placed around the piers to increase streambed resistance (direct method). However, in indirect method, some partitions such as collar slot and submerged vanes are used to reduce scouring caused by horseshoe vortex and downstream flow. In this research, effect of two types of square and circular collar on a single cylindrical model has been investigated. The results showed that using the two kinds of collar, especially below bed level decreased the scour depth. Square collar was more effective than circular one in decreasing the scour depth. The square and circular collars showed 70% and 50% decrease in the rate of scour depth, respectively, as compared to pier without any collar.