| As the development of offshore wind energy resources becomes saturated,it is an inevitable trend to develop offshore wind power for the deep sea.Under complex deep water environmental conditions,the stable sinking of the bucket foundation in water is an important part of the entire installation and construction.How to predict the movement characteristics of the bucket foundation during the settlement process and take corresponding control measures is the key to achieving the safe settlement of the bucket foundation.Based on the polygonal cylindrical foundation of an offshore wind farm,this paper started with the structure’s own characteristics and the influence of environmental parameters on the buoyancy of the foundation,established a bucket foundation-pontoon-stay cable-water environment multi-body coupling dynamic analysis model,explored the law of the movement characteristics of the bucket foundation in the submergence process,clarified the influence of wind,wave and current load on the movement characteristics of the bucket foundation,and proposed the calculation method of the extreme response of the air-floating bucket foundation in water and the control strategy for safe submergence:(1)A 1:60 static water settlement experiment was carried out on the polygonal bucket foundation,and the hydrodynamic characteristics of the bucket foundation under different settlement depths were studied.The study found that with the increase of the sinking depth,the stability of the bucket foundation increased continuously,the natural period of heave increased slowly,and the natural period of pitch continued to decrease,and the static stability reduction relationship between the real floating body and the air floating body is obtained.(2)Numerical simulation analysis was carried out on the movement characteristics of bucket foundation sinking in waves.The research results showed that when the top cover of the cylindrical foundation entered the water,due to the sudden change of body shape,the foundation sways and pitch changed greatly,and the heave changed little during the whole sinking process;The auxiliary sling cable force presented a law of first increasing and then decreasing during the entire sinking process,and reached the maximum value when the top cover approached the water surface.At the same time,the cable force value at the front wave was greater than that at the back wave;When the natural period of the foundation was close to the wave period,the two would resonate,making the response of the foundation reach the maximum value,which should be avoided as much as possible in actual construction and operation;Changing the heading angle of the foundation could effectively reduce the peak motion response of the cylindrical foundation,but it would cause the response of the cylindrical foundation with multiple degrees of freedom.(3)The analysis method of the dangerous state during the deep water settlement of the polygonal bucket foundation was established,and the posture control measures during the foundation settlement were optimized.The study found that when the natural period of the bucket foundation changed to coincide with the period of the external waves during the sinking process,the resulting motion response was relatively large.When determining the dangerous state,it was necessary to comprehensively consider the natural cycle of the cylindrical foundation and the changes in external body shape.When the initial angle of the lower cable was 30°,the response of the cylindrical foundation was smaller and the posture was better. |
