Study for predicting the earthquake-induced liquefaction around the monopile foundation of offshore wind turbines

Abstract

Earthquakes may cause liquefaction of seabed soil around the monopile foundations of offshore wind turbines (OWTs), posing a great threat to the safety of OWTs. As an accurate liquefaction prediction method has not been achieved today, a further study is conducted in this paper following the experimental investigation of the pore pressure development rule of the soil samples in an offshore wind farm. In the study, a new liquefaction discrimination method was proposed first based on the triaxial test results of the seabed soil samples. Secondly, a numerical model of monopile-supported OWT was developed in ABAQUS. Then, various seismic waves originating from the depths of the seabed were applied to the OWT to calculate the corresponding shear stress of seabed soil around the monopile foundation. Finally, the soil liquefaction around the monopile foundation in different seismic scenarios was assessed using the proposed liquefaction discrimination method. The research results show that the newly proposed liquefaction discrimination method is more accurate in estimating the critical anti-liquefaction strength. Severe liquefaction mainly occurs in the shallow soil layers around the OWT's monopile foundation. The monopile structure, lateral loads on top of the OWT, and bidirectional earthquakes will exacerbate the liquefaction of the seabed soil.