Study On Dynamic Analysis Of Bucket Foundation Structure And Foundation Soil Of Offshore Wind Turbine

As a kind of abundant, clean and renewable energy, wind energy is expected to increase significantly in the near future. Offshore wind turbine system is in the complex marine environment where it is affected by wind, wave and current loads, and even typhoons, earthquakes and other extreme loads which makes it technically demanding and costly development. Bucket foundation has a lot of advantages such as its applicable of different soils, its good stability, its high speed in construction and its recycle use, and so on. So it can be the important part of the highly efficient and low cost wind turbine system.Considering comprehensively the characters of support structures of offshore wind turbines, the dynamic response of the coupled system of wind turbine structure-bucket foundation-foundation soil is studied based on those existing in the literature. Main contents and conclusions in this thesis are summarized as follows:(1)Summarizing the types of the loads which offshore wind turbine suffered and simulating the wind, wave, current loads acted on the wind turbine structure and the foundation soil.(2)Select the experimental model in the literature, and establish the same ABAQUS model. Comparing the experimental result and the numerical result in order to prove the rationality of the numerical method.(3)Establish the numerical model the tower-bucket foundation-foundation soil under the combined effects of the wind?wave and current so as to analyze the response characteristics of the system. From the analysis we can see that the vibration of the tower is severe, and the maximum displacement occurs at the top of the tower. Comparing other loads, wind load controls the displacement of the tower. The response of the seabed near the bucket foundation is affected not only by the wave pressure, but also by the disturbance of the foundation. The response of the seabed away from the bucket foundation is mainly affected by the wave pressure. The amplitude of the excess pore pressure in the bucket foundation increases from top to bottom and from center to the boundary. The saturation, the permeability, Poisson ratio, void ratio of the seabed and the wave period, the water depth have a significant impact to the coupled system.(4)The paper uses the finite element analysis software ABAQUS to do the calculation and analysis of the system and define the range of liquefaction combining the anti-liquefaction shearing strength method. From the analysis we can see that the liquefaction of the seabed occurred between the depth from 0m to 11.85 m and from 12.5m to 15.9m under the seismic loads. The liquefaction inside and outside the seabed is different. After the liquefaction of the seabed, the bearing capacity of the bucket foundation is not enough.