Physical modelling of the stability of a revetment breakwater built on reclaimed coral calcareous sand foundation in the South China sea—random waves and dense foundation

Abstract

In the past several years, China has successfully constructed and enlarged several lands on the top of some coral reefs in the South China Sea (SCS thereafter) by the way of reclamation. A great number of revetment breakwaters have been built at the margins of these reclaimed coral reef islands, to defend these artificial lands from scouring and intensive wave impact. In order to quantitatively explore the dynamics characteristics, as well as the stability of these revetment breakwaters and their foundation under extreme wave impact, in this study, five large-scale wave flume physical model tests are conducted adopting a geometric similarity ratio of 1:10, to experimentally investigate the wave impact, displacement of the revetment breakwater, wave overtopping and the pore pressure in the dense calcareous sand foundation under the attack of random waves. Finally, the overall stability of the revetment breakwater is evaluated. The experimental results indicate that the maximum impact on the revetment breakwater applied by the fortified extreme waves reaches up to 6 kPa, the responding pore pressure in the dense coral sand foundation is not very significant, and the maximum volume of wave overtopping can be up to 0.39 m3/h per meter when there is no accropode installed to dissipate wave energy. There is no obvious deformation occurring in the dense foundation, and the displacement of the revetment breakwater is also not significant after long-term wave impacting. Combining all these experimental results, it is concluded that the revetment breakwater can stay stable under the condition of the fortified extreme ocean wave. However, the amount of wave overtopping is considerable, which would result in the delay of the process of the groundwater desalination in these reclaimed islands in the SCS. The test results further indicate that the usage of accropodes can considerably reduce the wave impact and the amount of wave overtopping.