Effect of Collar on Scour Reduction Around Abutments

Abutments are constructed to protect and control river banks. Studies show that methods of preventing and reducing scour are based on the scour mechanism. One of these methods is to set a collar around the abutment. Collars protect the bed against downward flow and vortex system developed due to the separation of flow at the upstream edge of the abutment and reduces the amount of scour. In this research, scour is considered around three types of abutments with 6, 8, 10 centimeters length. Trapezoidal collars with miscellaneous dimensions and fixing on bed surface under the clear water scouring conditions were also investigated and compared with the case of collars were not in use. The results obtained showed that increasing the collar width, improve the impact of collar on scour depth reduction and its time delay. The percentage of scour reduction for different collar width fluctuate from 15 to to 100.