While currently available methods of dynamic soil-foundation interaction idealize the soil as a continuum, this paper presents a general theory to obtain the dynamic response of offshore caissons resting on a saturated or nearly saturated poroelastic medium. The model, based on Biot\u27s theory, considers the compressibility of both solid and fluid phase and assumes that the fluid flow is governed by Darcy\u27s Law for an isotropic medium. Results are presented as plots of normalized amplitudes of displacement load or rotation-moment ratios for a rigid strip founded on a dense coarse sand. The results demonstrate that fluid compressibility, which is primarily a function of the degree of saturation, has an important effect on rocking motions. Soil permeability appears to have a rather minor effect on the response
