Wave Force Characteristics and Stability of Detached Breakwaters Consisting of Open Cell Caissons Interlocked via Crushed Stones

The maximum external force acting on a long continuous harbor structure can be reduced by controlling the phase difference of forces acting longitudinally. This strategy can be used to increase the structural stability of breakwaters consisting of caissons. Breakwaters have been developed using interlocking caissons to effectively respond to the constant increase in wave height due to climate change. In this study, we investigated the wave force characteristics and stability of a detached breakwater consisting of open cell caissons interlocked via crushed stones. We performed wave basin experiments and compared the results with analytical solutions of linear diffraction waves. The results revealed that the maximum wave force acting on the front of the breakwater decreased as the incident angle increased, reducing by as much as 79% for an incident angle of 30 degrees. Although the variability of the maximum wave force for each caisson is large owing to the influence of the diffracted waves, the maximum wave force acting on the entire detached breakwater was not significantly affected by this variability. The analytical solutions based on linear wave theory agreed with the experimental results, indicating that the findings can be applied to actual designs. The structural stability of the breakwater was enhanced, even for low incident wave angles, compared to that of a single integral structure, as the frictional resistance produced by the sliding structure increased due to the shear resistance between the filled crushed stones and the rubble mound.