Study On The Soil Liquefaction Of Bucket Foundation Of Offshore Wind Turbine Generator

Bucket foundation is a new maritime foundation structure with the significant advantages such as reusable, convenient construction and low cost. As the foundation of the offshore wind turbine generator, the bucket foundation bears a variety of dynamic loads during using,among these seismic load is the most influential and destructive one.Under seismic loads,the soil is possible to be liquefying,and then the strength and stiffness of the clay will be reduced,for the sand will be reduced to zero.So the bearing capacity of the overall structure was severely affected by the soil liquefaction.The purpose of the paper is to distinguish soil liquefaction areas under the seismic load,and calculate whether the whole bucket foundation structure is able to bear loads after soil liquefaction.The criterion of liquefaction used in this paper was the anti-liquefaction shearing strength method which was put forward by Seed and had been made some changes when used.The specific steps were:Firstly,according to the soil material parameters, used the existed experimental data and empirical formula to calculate anti-liquefaction shear stress of soil;then calculated the dynamic response of the bucket foundation structure and the soil by the finite element program and obtained the maximum shear stress from stress-time curve; distinguished the liquefaction areas with the unit of finite element; Finally, reduced the soil stiffness and strength in the liquefaction region, calculated the load-carrying state of the bucket foundation under ultimate load, compared with the state before liquefaction to determine whether the structure can be used after soil liquefaction.This paper used the finite element analysis software ABAQUS to do the calculation and analysis of the structure. The structure response under seismic load was calculated by the explicit analysis and simulate the soil infinite boundary using the infinite element provided by ABAQUS. It used implicit analysis method to calculate stress state of the structure under the ultimate state.It can be obtained that, some areas of soil of the depth from 0m to10m were liquefied under the seismic loads, at the same time the vertical static load on the bucket foundation had a significant effect to increase the anti-liquefaction ability of the soil under the bucket. By the allowed limit displacement criteria using in project, it obtained that the bucket foundation can still work after the soil liquefaction.