Laboratory investigation of flow pattern and scour around rectangular bridge abutment in case of using collar

Various studies have been done recently on the mechanism of scour around hydraulic structures, especially bridges. In the case of scour around bridges, researches have had more focus on scour of piers in compare with abutment. While, the review of available information on bridges break indicated the major problems were related to abutment. Therefore, most costs have been spent in this part. One of the methods of scour reduction around the bridge abutment is using collar. In this research the effect of dimensions and position of collar installation were investigated on abutment scour reduction. Results showed that increasing dimensions of collars increased the efficiency of performance. Also, results revealed that the collars located under the bed had better performance than the other collars located on the bed and above it. Following this research, three-dimensional components of velocity were determined with electromagnetic velocimeter around abutment with collar and used for drawing flow pattern. Result showed that down flow and generated vortex were effective parameters on abutment bridge scour and collar had effective role on reduction of scour abutment with controlling down flow and causing resistance in bed against generated vortex.