Experimental Investigation of Unsymmetrical Netted Collar Performance on Local Scour Reduction around Bridge Pier with Circle Section

Researches show that one of the most effective factors on bridge destruction is bridge pier scour. That one of the methods used to reduce of scour around bridge piers is installing collar. The collars protect the river bed against vortex flow in the vicinity of the piers. In this research, the role of collar as a control structure of bridge pier scour was investigated along with the effect of its shape. Therefore, dimensions of collar were investigated on bridge pier scour reduction and application diagrams proposed. Results show that increasing dimensions of collars will increase the efficiency of performance comparing of both collars indicated, that collar with dimensions have better performance in reducing scour than collar . Larger collar does prevent sediment movement due to lift vortex in downstream of bridge pier and for this reason. On the other hand, with decreasing roughness at the surfaces collar from 40% to 50%, the reduction of scour increases from 39% to 58%.