Local Scour Reduction around Cylindrical Piers Using Permeable Collars in Clear Water

To address the shortcomings of solid collar, mainly potential risk deformation and damage due to its weight after overhanging above river bed caused by local scour, a lighter form scour reduction measure, permeable was proposed. The aim reduce depth around cylindrical piers, total 20 tests were conducted in this study. First, influence porosity collar on efficiency studied under condition constant size installation height, diameter, thickness based indoor model experiments. Then, optimal porosity, order. results show that has great reduction. increases first then decreases with increase porosity. When is 50%, effect best, can reach up 78.1%. height best when placed surface riverbed, which close using riverbed. rapidly diameters are less than 3.5 D (D diameter bridge piers) slows down until tending 100%. thickness, 0.15 D, 89.6% give perspective depths piers.