Analytical model of the response of a composite-type caisson breakwater and seabed to waves

The response of a breakwater and the underlying seabed in the presence of waves has been recognized as an important design problem in the field of harbor and coastal engineering. In this research, a model is developed on the basis of an analytical method for the response of a composite-type breakwater sitting on a poro-elastic seabed and subjected to loading from water waves. The model utilizes the mixture theory and approximation method to describe the behavior in the seabed and the rubble mound base of the breakwater. Because of the complexity of the response, the problem is approached by allowing linearity to decompose the problem into scattering and radiation modes. That is, in the scattering mode, it is assumed that the breakwater is fixed and that the forcing part is the wave-induced pressure along the exposed surface of the soil. On the other hand, in the radiation mode, it is assumed that there are no waves and that the forcing part is the caisson's own motion. The model is characterized by solving each decomposed problem using a complex Fourier series technique. Computation time is limited to just resolving the simple inverse problem, leading to a clearer analytical description of the response vs. earlier, purely numerical approach (e.g. Finite Element Models). The analytical model is checked for its applicability by carrying out test calculations. Then, it is verified, first, by comparison with an analytical solution of the simpler problem of a caisson on a seabed and secondly, by comparing it with a finite element solution for the response of a composite-type breakwater (caisson on a rubble mound base). In both cases, the comparisons are in good agreement for pore-water pressure.