Study On The Effects Made By Composite Bucket Foundation Of The Offshore Wind Turbine On Soil Liquefaction Resistance

In recent years, the development and utilization of offshore wind energy has beenpaid more and more attention. As a new type structure of offshore wind farm, bucketfoundation has the advantages of simple construction, easy recycling and so on. Theapplication of it is very promising. However, China is an earthquake prone country,the offshore soil’s condition is complex and often contains much water. In earthquake,the saturated sand and silty sand is likely to occur liquefaction, which also causes theloss of the bearing capacity. This will have a very negative impact on the bucketfoundation and the upper structure. On the other hand, bucket foundation is a semi-opening base having soil inside and outside of it. In the earthquake, the existence ofbucket foundation will have a great influence on the dynamic performance of thesurrounding soil. Therefore study the effect and find out the main influencing factors,by changing these parameters to improve the security and stability of bucketfoundation and the soil’s together working, is crucial to increase the applicability ofbucket foundation in offshore wind farm.By using the anti-liquefaction shear stress method which has widely applicationand combined with finite element software ABAQUS, this paper compares the soilunder bucket foundation, gravity foundation and shallow foundation in the earthquake.By analysis the stress, displacement and liquefaction of the situation and finding outthe similarities and differences, this paper will point out the superioriies for the bucketfoundation in improving the soil liquefaction resistance compared to other foundations.The method mentioned above to study of the liquefied soil is based on total stressand can’t distinguish the effective stress and pore water pressure. In this paper, soil isbuilt by using porous media model in the finite element software ADINA. It regardssoil as a two-phase medium composed of soil particle and pore water, this is close tothe reality. Thus from the perspective of effective stress principle, when the excesspore water pressure equals soil initial stress, the soil effective stress is0. Theliquefaction happens and we can make the judge according to this. Compared with theanti-liquefaction shear stress method, this method can distinguish the effective stressand pore water pressure in the soil. It can better analyze the variation of excess porewater pressure in the soil caused by earthquakes and find out the specific role ofbucket foundation in soil liquefaction.In addition, by changing the aspect ratio of bucket foundation in saturated sandand studying the growth of the pore water pressure, the soil settlement and soilliquefaction under the foundation, this paper found out the rule of the effect that thebucket foundation made on the soil liquefaction. This will make contributes toimprove the work performance of the two under earthquake and provide reference forthe design and selection of the bucket foundation in the offshore wind farm.