Effect of Submerged Plates on the Dynamic Response and Sliding Simulation of Caisson Breakwaters

A theoretical study was conducted to investigate the effect of submerged horizontal plates on the performance of a vertical breakwater during the failure process by simulating the caisson sliding under impulsive wave loads. Various rear plate arrangements were investigated, attending to submersion depth, and compared with the results from the absence of a plate (typical vertical caisson) and a plate located at the water surface. A semi-analytical model developed by the authors based on the piston-type wavemaker theory and the application of the boundary-point selection method was upgraded to estimate the hydrodynamic characteristics due to the fluid–structure interaction and simulate the sliding of the geometries object of study. The analysis results confirmed the critical influence of uplift forces on the sliding calculations and the importance of including the memory-effect function. A slight reduction of the overall displacement of the structure was observed for plates nearest the surface, while the positive effect of the hydrodynamic coefficients’ horizontal components on the sliding was drastically reduced by the vertical ones. Additionally, new aspects of the boundary-point selection method were discovered, and some recommendations were given for its application in the velocity potential and sliding calculations for submerged plates.