Dynamic Wave-Induced Settlement Behavior of a Caisson Breakwater Built on a Sandy Seabed

Monitored breakwater settlements taken from an actual breakwater structure over an extended period of time (more than five years) were analyzed. The analysis revealed that the waves clearly affect the settlement of the breakwater, especially during high wave conditions such as typhoons. Breakwater settlement is caused by a decrease of effective stress of seabed during partial liquefaction due to wave-induced cyclic loads, which occurs due to an increase in excess pore pressure and the combination of oscillatory and residual pore water pressures. A new combined numerical model was suggested that allows the storm wave-induced seabed settlement underneath the caisson breakwater to be examined qualitatively. The technique uses a combined wave model (2D-NIT) and soil model (FLIP). The dynamic wave load calculated by the 2D-NIT was used as the input data for the soil model. This soil model can simulate both oscillatory and residual pore water pressures at the same time. There is a different feature to other previous studies adopting similar techniques.