The magnitude of impulsive pressure internsity is quite large, being several times that of ordinary wave pressure. However, the shear force at the caisson bottom, which is the effective pressure producing caisson sliding, is greatly reduced due to the caisson's dynamic response. The present study uses model experiments and non-linear FEM calculations to elucidate the characteristics of such a dynamic response.
　The dynamic behavior of model caisson was experimentally measured in a wave channel. The shear force occurring at the bottom of the model caisson was found to be significantly reduced by its dynamix response. The ratio of the peak shear force to the peak impulsive force.
　To reproduce the dynamic response of the caisson, we adopted a FEM calculation method named the Bank Earthquake Analysis with Dynamic Water Pressure(BEAD). The corresponding FEM-calculated results using the same impulsive wave force indicate good agreement with experimental results.
　In actuality, sand bed and rubble mound are relatively soft in comparison with those of the model, and therefore, the dynamic response is much more significant.