Stability of Armor Units on a Harbor-Side Mound Against Wave Overtopping With Backward Parapets

Abstract

The high mound is sometimes constructed behind a composite breakwater in order to increase the sliding resistance and utilize the mound for an aquacultural purpose. The high mound must be covered by armor units with adequate weight to prevent from scattering by overtopping waves . However, the shallower is the submerged depth of the mound, the heavier become the armor units.This study proposed a backward parapet as a countermeasure to reduce weight of armor units . A numerical simulation showed the difference in the velocity field behind the caisson between the backward and forward parapet. With the backward parapet, large-scale eddies were not observed and the velocity on the mound was slower than that of the forward parapet. Furthermore , hydraulic model tests showed that the stable weight was approximately 40% less than that of the forward parapet .