A Study On Bearing Capacity Behavior Of Suction Multi-bucket Foundation For Offshore Wind Turbine

Wind power generation system is an important form of using wind power as well as a more mature sort of many renewable energy technologies.Wind farm includes two kinds, land and sea.The offshore wind farm,with its high-speed,low turbulence,high-yield and other advantages,has been concern around the world.As a new type of deep-water offshore foundation,suction bucket foundation has been gradually used in the design and construction of offshore wind turbine.However,the research results of previous work principally focus on the analysis for stability of suction single bucket foundation,and the behavior of bearing capacity and joint-work mechanism of suction multi-bucket foundation have been not well understood.Bucket foundation is not only subjected to the long-term action of vertical load induces by all weights of offshore platform and equipment,but also is imposed by both horizontal load and moment caused by wave and earthquake.Therefore,in view of the load characteristics of offshore wind turbine,it will be theoretically important and practically significant to examine the failure mechanism and to work out effective methods for evaluating beating capacity behavior of suction multi-bucket foundation under monotonic and combined loads.In this dissertation,the studies are emphasized on numerical methods for evaluating the beating capacity behavior and failure mechanism of suction multi-bucket foundation in soft ground under monotonic and combined loads.The main investigations consist of the following two parts.1.Based on general-purpose finite element software ABAQUS,the three-dimensional elasto-plastic total stress finite element model for suction tripod bucket foundation and the surrounding soil on homogeneous soft ground is established as a special case in this paper, The ultimate bearing capacity of suction tripod bucket foundation imposed by monotonic load such as horizontal,vertical and moment load is evaluated by displacement-controlled method. The most disadvantageous and the most advantageous directions of horizontal and moment bearing capacity behavior of suction tripod bucket foundation are determined.According to vertical load as well as the most disadvantageous horizontal load and moment,the failure mechanism of tripod bucket foundation is evaluated for different bucket distance.Considering two kinds of working conditions,the joint-work mechanism of tripod bucket foundation is investigated by comparing with the ultimate beating capacity of single bucket foundation under monotonically loading pattern with the same parameters.Moreover,by parametric computation and comparative analysis the ultimate bearing capacity of suction multi-bucket foundation under monotonic load is evaluated for different undrained shear strength of soil and effective unit weight of soil.2.Based on the loading procedure of Swipe test and fixed displacement ratio,the bearing capacity behaviors of tripod bucket foundation under combined loads are investigated by FEM and the V-H,F-M,M-H failure envelopes of tripod bucket foundation are searched.The failure mechanism of foundation under different load component is compared for different bucket distance.Furthermore,according to two actual working conditions of Hangzhou Bay wind farm,the feasibility of design scheme for multi-bucket foundation is evaluated and failure envelopes are plotted to assess the foundation stability.