Scour countermeasures around cylindrical pier by using downscaled W weir

Scour is a significant concern for bridge design/maintenance, and scour countermeasures are often used to prevent or reduce erosion caused by scouring. The W weir is a grade control structure serving many purposes, including scour control at bridge piers. A series of laboratory experimental runs was conducted, changing the size, height and location of the pier in relation to the weir to optimise the structural configuration of the downscaled W weir. These experiments revealed that the scour hole profile upstream of the downscaled W weir changes with weir height. At a weir height of 1.0D (D = diameter of pier), two small depressions of almost identical size were observed inside the main scour hole, one just in front of each upstream apex of the W weir. One cone-shaped scour hole was observed when the W weir height was 0.5D with its maximum depth in between the upstream apexes. Reduction of scour in front of the pier was greater when the weir height was 1.0D. The maximum scour control achieved among all different structural combinations of downscaled W weir was 47.66%. This was achieved when the downscaled W weir was 2.0D in size and 1.0D high, placed 2.0D distant from the pier.