Case Studies I

Van Oord DMC was awarded the Contract for the Design and Construction of the Addu City Development project in the Maldives. The design of the shore protection works has been verified by means of 2D physical model testing at DHI in Denmark. 
The steep foreshore and shallow reef flat (very typical for atolls) caused extensive shoaling and wave breaking, resulting in significant water level set-up and low-frequency waves on top of the reef flat. These nearshore wave transformation effects were dominant for the measured overtopping discharges, which could not be predicted or reproduced with existing overtopping calculation methods. Also, the magnitude of the water level set-up and the confined volume in the wave flume created a water level set-down near the wave generator. Therefore the offshore water level had to be corrected and calibrated by adding water to the flume at the start of the test.

The Cubilok™ is a new trademarked armour unit that was developed in South Africa by PRDW to cater to a range of breakwater designs. As part of a master's research study, 2D physical model tests were conducted to investigate the stability and behaviour of the Cubilok™ on a 3V:4H slope. This investigation revealed that wave steepness significantly influences the performance of the Cubilok™, with superior stability observed during conditions with shorter wave periods. When simulated with a packing density of ɸ = 0.63, the stability of the Cubilok™ is comparable to other armour units, however it is prone to significant settlement. Further findings indicated that the stability of the Cubilok™ greatly improves when placed on a 1V:2H slope, where all movements, including rocking and settlement, were reduced to near negligible amounts. This suggest that the Cubilok™ might be a more suitable alternative for designs where milder slopes are required.

The paper provides background on the Hanbar concrete armour unit which has been used since late 70s in Australia and more recently in New-Zealand. Guidelines for installation, including placement density and damaged coefficient, based on over physical modelling and field installation on over a dozen breakwaters are presented. The paper concludes with two recent case studies which have successfully capitalized on the economical, robustness and manufacturing simplicity of the Hanbar concrete units. The first study details the integrated physical modelling (2D and 3D at scale 1:40) for the Ōpōtiki Harbour Development in New Zealand. The second study provides an update on laboratory and field trials of high-density geopolymer concrete Hanbars units.

The current findings highlight that the Frioul port breakwater is seriously damaged and must be rehabilitated. Accordingly, the rehabilitation solution, which consists to replace the actual rock armour unit, was physically modelled, and tested for its hydraulic stability and the overtopping performance as well as the forces and pressures acting on the crown wall. The process includes recreation of breakwater cross sections in a 2D wave flume at a scale of 1:35, and a optimized breakwater configuration proposed in a 3D wave basin at a scale of 1:50.
These two campaigns made it possible to compare and optimize the design, first with the state of the art (Van Gent, M., et van der Werf, I., 2019) (Mares-Nasarre and van Gent, M., 2020), then with the observations and measurements collected from the modeling.