Analysis of Scour around a Group of Vertical Piles in the Field

Abstract

A study of the scour around a group of piles in the field exposed to oscillatory waves was carried out. The main purpose was to derive simple predictive formulas for the geometric properties of the scour hole in terms of nondimensional parameters describing the flow, sediment, and pile characteristics. A comprehensive data set from the Pacific coast of Japan was employed where the beach profile along a pier experiencing scour around its piles was surveyed every week. Detailed wave measurements were available, and only the outer piles exposed to nonbreaking (oscillatory) waves were investigated. The maximum scour depth showed a distinct correlation with the Keulegan-Carpenter number, and an empirical relationship was derived that agreed with some earlier laboratory experiments, if an equivalent diameter was defined for the pile groups. The width of the scour hole displayed little correlation with the Keulegan-Carpenter or other nondimensional numbers employed, although it should be noted that only one pile configuration was investigated in the present study.