DRUM CENTRIFUGE TESTS ON COUNTERMEASURES AGAINST WAVE-INDUCED LIQUEFACTION AROUND OFFSHORE MONOPILE

Abstract

 This paper discusses the experimental findings pertaining to the build-up of residual pore pressures around an offshore monopile foundation leading up to liquefaction and the effects of gravel cover replacement around the pile on the stability of the foundation. A range of wave tests using a drum centrifuge was performed under a centrifugal acceleration of 70 gravities. It was found that liquefaction firstly occurred at the side of the monopile against the direction of progressive waves, which indicates the significance of the rotation of principal stress axes as well as the restriction of the partial drain in the sand. The gravel layer replacement with a range of 2 times of usual scour protection could not prevent the occurrence of liquefaction and the collapse of monopile under severe wave conditions. This indicates the significance of embedment of the monopile in the dense layer in addition to the scour protection.