ABSTRACT
A gravity caisson breakwater is a hollow concrete box which is in filled with sand after it has been placed at the desired location. It is primarily built to provide protection against wave attacks and at the same time reduce the amount of dredging required around a harbour entrance. The recent development of harbours and related activities in deep waters lead to an increasing demand for vertical breakwaters. Oumeraci (1994) reviewed a number of breakwater failures and established that wave breaking and breaking clapotis represent the most common source of disasters experienced by vertical breakwaters. Caisson breakwaters are conventionally designed by considering the wave loading as a quasi-static load and then checked for their stability against sliding, overturning and bearing capacity failures. However, the breaking wave loads are dynamic hydraulic loads with very short durations and very high peak loads that may exceed the quasi-static wave load by over 10 folds. The failures of caisson breakwaters in Japan reported by Hitachi (1994) and Takahashi (1994a) may be attributed to the severe impacts created during wave breaks. Hence, conventional design methods may not be appropriate for caisson breakwaters.
