Effects of different armour units and placement methods on wave loads acting on crown walls in shallow water

Date

2026-07-15

Author

Demir, Furkan
Güler, Hasan Gökhan
Korkmaz, Alperen Mulayim
Erler, Berkay
Tarakcioglu, Gulizar Ozyurt
Baykal, Cüneyt

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This study presents a comprehensive experimental investigation into the effects of different armour unit types and placement configurations on wave-induced loads acting on the crown walls of mound breakwaters under shallow-water conditions. A total of 420 physical model tests were conducted under irregular wave conditions, encompassing twelve armour configurations: eight with Antifer units, three with tetrapods, and one with rock armour. The experiments also varied crest elevations and breakwater slopes (1:1.5 and 1:2) for the Antifer configurations. Well-established empirical wave load formulas (Pedersen (1996) and Nørgaard et al. (2013)) from the literature were evaluated, and the coefficients in the Nørgaard et al. (2013) formulation which was developed as a shallow-water adjustment of the well-known Pedersen formulations were modified to represent the influence of armour type and placement pattern for Antifer and tetrapod units. In addition, hands-on computations using the modified coefficients were performed to illustrate the effects of armour units and their placement patterns on wave loading. The experimental results show that the rock armour measurements align closely with the original Nørgaard et al. (2013) formulas. Both the Antifer and tetrapod units and their placement methods significantly affect wave loading components. Using the modified coefficients in wave load estimations markedly reduced sample standard errors compared to the reference studies. Among the Antifer placements, closed pyramid and double pyramid arrangements generate 10%–20% higher forces on average than irregular placement. For tetrapod units, the configuration with large gaps between units (TP1 method) produces up to 45% higher horizontal forces on average, whereas more compact arrangements lead to reduced loading. Measured vertical forces are generally overpredicted by the conventional triangular base-pressure distribution. Finally, computations with the modified coefficients show that most configurations produce higher horizontal wave forces than rock armour, with the TP1 placement method nearly doubling the corresponding rock armour case.

Subject Keywords

Antifer, Crown wall, Mound breakwater, Physical model tests, Placement methods, Rock, Tetrapod, Wave forces

URI

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=105036422542&origin=inward
https://hdl.handle.net/11511/119221

Collections

Department of Civil Engineering, Article