An Experimental Study of Characteristics of Solitary-Wave-Induced Scour Around a Pile Breakwater with a Discussion on Effects of the Distance between Piles

Abstract

Understanding tsunami-induced scour at a pile breakwater is important for the foundation safety of this type of coastal defense structures. A series of wave-flume tests were performed for [Formula: see text], with [Formula: see text] being the gap size and [Formula: see text] the pile diameter, to study the characteristics of the solitary-wave-induced local scour around a pile breakwater, including the scour-hole depth, scour-hole length, deposition sandbar height and the scoured volume. It was found that the jet flow through the gaps between piles caused the local scour around individual piles. A more or less two-dimensional deposition sandbar was found on the down-wave side of the pile breakwater in the later stage of the scour process. A new empirical equation was introduced to approximate the evolution of the depth of the scour hole induced by a series of solitary waves. The equation was verified by existing data reported in the literature for [Formula: see text] and the new data reported in this study. Effects of the distance between piles on the characteristics of the local scour were discussed by comparing the results for [Formula: see text] and 0.39. The comparison showed that the scour-hole depth and height of the sandbar for [Formula: see text] were all noticeably larger than the corresponding values for [Formula: see text].