Work

Structural and hydraulic response of emerged low-crested cube-armoured breakwaters

Year: 2025

Type: article

Abstract: Increasing water levels, wave heights and storm frequencies due to global climate change are driving the need for more resistant coastal structures, adaptation measures and improvements in the design of low-crested breakwaters. These structures can not only protect coastal areas against erosion but also protect other conventional coastal structures such as port structures and flood protection structures. In this study, the structural and hydraulic behavior of statically stable emerged low-crested cube-armoured breakwaters were investigated by performing physical model tests. This research considered cube armour layers with irregular placement in a double layer and cube armour layers with a regular placement in a single layer. For the single layer two different packing densities were tested (y=0.59 and 0.67) because optimizing the packing density is relevant for the ease of construction, lowering the environmental impact and for the costs of cube armour layers. Low-crested structures with various crest widths have been tested. The results show that for cube-armoured low-crested breakwaters with irregular placement, the cube dimensions can be significantly reduced compared to conventional rubble mound breakwaters with higher crests. The structural stability of low-crested breakwaters with single-layer regular placement showed different responses compared to the irregular two-layer case due to the geometric discontinuity at the intersection of the front slope and crest. Although a regular placed single armour layer is more stable than an irregular placed double armour layer with the same packing density (y=0.59), damage to the crest caused instability of the structure for the single armour layer. While for this packing density damage occurred both at the front slope and at the crest, for a higher packing density of the single armour layer (y=0.67), damage occurred only at the crest. For the hydraulic behavior of low-crested breakwaters with cube amour layers, the incident wave conditions, the freeboard (Rc) and crest width (B) are the most important parameters. It is evident that for low-crested breakwaters, the wave transmission increases but the reflection decreases compared to conventional breakwaters with a high crest. Based upon a re-evaluation of expressions given in literature on wave transmission and wave reflection at rubble mound low-crested breakwaters, guidance on applications for cube-armoured structures has been provided. This study provides further information for engineers and researchers on the structural and hydraulic response of low-crested cube-armoured breakwaters.

Source: Applied Ocean Research

DOI: 10.1016/j.apor.2025.104488