Kim, Y.T., Lee, J.I. and Heo, J.W., 2007. Stability of armour block at Starting Part of Seawall. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 1029 – 1033. Gold Coast, Australia, ISSN 0749.0208

The purpose of the research is to investigate hydraulic stability of the seawall at Jungjuk Island, which is a part of the Busan-Geoje Fixed Link Project in Korea. Jungjuk Island is exposed to extreme waves and high water levels during typhoons from southerly directions. The main function of the seawall is to protect immersed tunnels and tunnel portal structures from the heavy wave impacts and flooding. In this study, a series of experiments were performed to investigate stability of various designs for the seawall and an optimum cross section among the proposals was suggested.

Hudson formula or van der Meer formula (CIR/CUR, 1991) is normally used to assess weight of armour blocks for perpendicularly incident waves. The experiments showed that the design of the seawall based on the formulas were comparatively stable enough to satisfy the design condition for the trunk part where waves propagated almost perpendicularly. However, the design was found to be not stable enough for the starting part where strong wave breaking induced currents and big waves due to the geomorphologic characteristics occurred and impacted the seawall. For usual breakwater designs, the weight of an armour block used at a head part is 1.5 times that at a trunk part, whereas there are no regulations for a starting part. From the laboratory study, this research suggests there is a need to consider the area (starting part).