Scour Reduction by Air Injection at a Cylindrical Bridge Pier: Experimental Determination of Optimal Configuration

Abstract

To reduce bridge scour-induced collapse, experiments were performed to determine the optimal ratio of air to water velocity values for the least amount of scour at a cylindrical bridge pier. Clear-water experiments were done in noncohesive soils with air injected by means of a horizontal, semicircular air diffuser on the upstream half of the pier at the level of the original sediment prior to scour initiation. The diffuser location, number, and size of holes were determined previously to be optimal. Of the air-to-water velocity ratios tested, it was found that the least scour occurred at a ratio of 57.1. Scour was reduced 35% over the case with no air injection.