Novel protective equipment is developed to reduce local scour around bridge piles under coastal environment. Series of experiments are carried out in a wave flume and a current flume for single pile and twopile group with or without the protective equipment under steady current and monochromatic waves to study the properties of new equipment. As a result, the erosion depth around the single pile is in direct proportion to the wave height, wave length, pile diameter, and flow velocity of current, but in inverse proportion to water depth and collar diameter. It is concluded that the protective equipment present here can reduce the depth of local scour effectively for either single pile or two-pile group. A moderate height of protective device is benefit for reduction of scour.
In recent years, several bridges across the sea are built in Yangtze River Delta region. Piles are widely used in practice to support marine bridge structures. However, scour around piles may reduce the stability of bridge structures. Local scour of sediment around piles of marine bridge has been studied extensively for several decades. The scour mechanism around a circular pile is mainly analyzed on the basis of fluid mechanism and a vast amount of experimental work is performed on local scour. A systematic introduction to the mechanics of scour of the pile in the marine environment is presented in a book by Sumer and Fredsoe (2002). The complex three-dimensional separation of the flow upstream of the cylinder and the periodical vortex shedding in the downstream region is used to explain the local mechanism. Since the existence of scour around piles may reduce the stability of bridge structures, there is a significant interest in finding reliable ways to reduce scour depth of piles and efforts have been made to reduce scour.