Two simple seismic isolation systems that leverage buoyancy or excess pore water pressure generated due to liquefaction have been devised for spread foundation structures. Through dynamic centrifuge model tests, it is shown experimentally that a sliding isolation effect arises during seismic loading if buoyancy force of appropriate magnitude acts on the underside of the foundation. It is confirmed that seismic isolation performance tends to improve as the buoyancy-to-weight ratio increases. Performance with buoyancy-to-weight ratios of 90% or more is particularly good, and the maximum response acceleration of a structure can be reduced to below 100 cm/s2 against a sinusoidal wave with a maximum acceleration of 500 cm/s2.
