Abstract
This paper discusses the experimental findings pertaining to the instability of the offshore monopile foundations due to wave-induced liquefaction in sand beds. The emphasis of the experiments was placed on investigating the relation between the occurrence/propagation of liquefaction and the increase in the displacement of the monopile, leading to collapse under the action of severe traveling fluid waves. A range of wave tests using a drum centrifuge was performed under a centrifugal acceleration of 70 gravities. It was found that the monopile put on the bed base started moving significantly upon the progress of liquefaction to the soil depth corresponding to the 1/3 of embedment depth of the monopile. The experimental results also show the effects of embedment to the dense layer and the significance of rotation of principal stress axes.
