Evaluation of the amount of the deformation is important for the performance-based design of caisson type breakwaters. However, the evaluation method of the deformation except for the sliding failure mode has not been established yet. In this study, authors discussed the applicability of soil spring model to the performance assessment method against foundation failure of breakwaters. As the result, it was shown that nonlinear soil spring model well explains the vertical displacement and inclination angle of breakwaters observed by a past hydraulic model experiment.
