Analysis of Motion of a Large-Scale Floating Caisson Under Regular and Irregular Waves

Caisson breakwaters for outer harbor facilities are considerably affected by wave conditions, rendering the control of caisson motion difficult. Numerical analysis was used to investigate the reproducibility of a large-scale floating caisson for a case study of installation in the Port of Kochi, Japan, and to study its dynamic characteristics under irregular waves. This analysis was performed using CADMAS-STR (Arikawa in Development of numerical wave tank coupled with structure analysis based on FEM 2009, pp 775–780, 2021), a three-dimensional numerical simulator for solid–gas–liquid three-phase models based on the Navier–Stokes equations. To verify the accuracy of this analytical method, we compared the results of the analysis with those obtained from field observations of the caisson sway at each stage of the sinking process. The results showed that the data could be reproduced within a range of ± 20%, except for some conditions. The correlation between the bottom clearance and motion amplitude was verified in terms of the effect of the natural period. An analysis of the motion under irregular wave action showed that the longer the wave period, the larger the motion amplitude. The feasibility of installation was evaluated based on the limit amplitude and the limit wave height for installation, and the results were consistent with those obtained for the installation at the Port of Kochi.