Abstract
The crest of a breakwater is often equipped with a crown wall with multiple functions such as a border of the pedestrian walkway, support of the rubble mound or concrete armour units, and reduction of the wave overtopping over the structure in storm conditions. However, the knowledge on how a crown wall influences the overtopping discharge is yet still limited. EurOtop (2016) advises to take the maximum of the crest freeboard Rc and the armour freeboard Ac in case a crown wall is present, and to use the average between Ac and Rc when no crown wall is present. This advice is based on expert judgement rather than on experimental research. The goal of the present work is to carry out experimental research and confirm or update the advice on overtopping over a crown wall for rubble mound structures.
Highlights
A breakwater according to Figure 1 is built on scale in both flumes
For the most common breakwater geometry, with a crown wall above the armour crest, test results show that EurOtop (2016)’s advice underestimates the measured overtopping discharge
The research performed (326 tests) has resulted in a more consistent advice for all different variations. This lead to an influence factor to account for the wall height, the crest width and the combined effect, to replace g* in Eq (1): γ9 = exp γ?@ABC = 0.0695 − 0.274 ln γ?@ABC_9 = γ9. γ?@ABC
Summary
A breakwater according to Figure 1 is built on scale in both flumes. The crest width in front of the crown wall is varied (Gc = 1P, 3P, 5P with P = Dn50). The water level, the wave height and the wave period are varied in the test matrix.
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