Study On Bearing Characteristics Of Four-bucket Jacket Foundation For Offshore Wind Turbine In Sand

As a new foundation of offshore wind power,four-bucket jacket foundation has the advantages of high structural strength,high bearing capacity,easy installation and disassembly,and is also apply to the deep sea area of 30-50m.It conforms to the trend of offshore wind power development towards the deep sea,and can better solve the problems faced in the development of far-reaching marine wind energy resources.However,at present there are few studies on its bearing characteristics.In this paper,the bearing characteristics of four-bucket jacket foundation in sand were carried out from two aspects: laboratory test and finite element numerical simulation.The main research contents and results are as follows:The horizontal bearing capacity model test of the four-bucket jacket foundation was carried out in the sand model experiment soil tank in the laboratory,and the effects of different loading angles,negative pressure of the bucket foundation and different loading speed on the horizontal bearing capacity of the four-bucket jacket foundation were studied.The results showed that the horizontal bearing capacity of the bucket foundation without negative pressure is 51.3% lower than that of the bucket foundation in sealing condition,and the loading speed has a direct influence on the bearing capacity of the foundation,the ultimate horizontal bearing capacity increases with the increase of loading speed.Through the comparative analysis with the finite element,it was found that the most favorable loading direction was along the diagonal direction,and the most unfavorable loading direction was along the axis direction.The finite element software was used to establish the models of four-bucket jacket with different aspect ratio and bucket spacing,and the bearing characteristics of the foundation under the monotonous load such as vertical,horizontal,bending moment and torque were compared and analyzed.The results showed that under the vertical load,the four-bucket jacket foundation is mainly based on the bearing of the bucket top,and the aspect ratio has a greater impact on the bearing mode of the foundation;under the horizontal load,bending moment and torque,the aspect ratio and bucket spacing are almost linear with the bearing capacity of the foundation;under the horizontal load,the vertical position of the rotation center of the four-bucket jacket foundation with different aspect ratio and bucket spacing is from 0.86～0.92L below the top of the bucket,and under the bending moment load,it is from 0.68～0.73L.Based on the study of the bearing characteristics of four-bucket jacket foundation with different aspect ratio and bucket spacing under combined bearing mode.The following results were obtained: the existence of vertical load can effectively improve the horizontal load,bending moment and torque bearing capacity of the foundation.With the increase of vertical load,the horizontal load and bending moment bearing capacity of the foundation first increased and then decreased,while the torque bearing capacity has been increasing slightly.Finally,the three-dimensional failure envelope of the foundation under V-H-M combined loading mode was calculated to further define the combined bearing capacity of the four-bucket jacket foundation.