CONTROL OF LOCAL SCOUR AROUND BRIDGE PIERS USING CURRENT DEFLECTOR

Scour around bridge piers is one of the most important fields of hydraulic research. The scour phenomenon may endanger the whole structure after long or short run depending upon the extent of scouring processes. So, the present paper introduces a tool which maximizes the reduction of the maximum local scour around bridge pier and hence ensures greater safety of the structure against the harmful local scour around the bridge pier, and hence longer life of the structure is expected. A rectangular collar of fixed width was used. Current deflectors with different heights, different lengths and different angles of orientations were tested to obtain the design criteria of the deflector that maximize the reduction in the scour dimensions and a maximum protection against scour is achieved. Each deflector setting was tested under similar subcritical flow conditions with tail Froude number ranging from about 0.2 to 0.55. A recirculating flume with 4m length, 20cm depth and 60cm width was used to conduct the experimental work. Water surface and scour profiles were measured and analyzed. A statistical equation was developed and proposed to predict the maximum relative scour depth around the bridge pier. It was concluded that the use of the optimal height of the deflector is 1.5 the pier width, the optimal length is 0.33 the pier width and the optimal angle is 0.23π. These criteria greatly reduce the maximum relative scour depth around the bridge pier to the extent of 80% when compared to the no collar cases. While the same criteria produce an additional reduction of about 20% in the relative maximum scour depth compared to no deflector case if the deflector is fixed on a rectangular collar with width of 3 times the pier width.