Study On Bearing Capacity Behavior Of Pile Foundation For Offshore Wind Turbines Using 3-D FEM

With the development of wind power generation technology,offshore wind power generation plays a major role of developing renewable sources in the world today.Offshore wind turbines platform comes from traditional oil and gas platform. The foundation is not only subjected to the long-term action of vertical load induced by all weights of platform and equipment,but also is imposed by both horizontal load and moment caused by wind and wave as well as current.Compared to traditional oil and gas platform foundation,the vertical load is much smaller,and as a proportion of the vertical load the horizontal load and overturning moment are much larger. However,because the offshore wind farm has been developing for only 17 years,the studies of bearing capacity behavior of pile foundation for offshore wind turbines subjected to combined loads haven't been well clarified and there are lots of works to be done for our engineering.Therefore,it will be theoretically important and practically significant to examine the working mechanism and failure pattern and to work out effective methods for evaluating bearing capacity behavior of pile foundation for offshore wind turbines under combined loads.In this paper,the studies are emphasized on numerical methods for evaluating the bearing capacity behavior of pile foundation for offshore wind turbines under combined loads.The main investigations consist of the following parts.1.Based on general-purpose finite element software ABAQUS,the finite element computational model of mono-pile foundation for offshore wind turbines under monotonic loading is established.The ultimate bearing capacity of mono-pile foundation for offshore wind turbines subjected to monotonic load such as horizontal, vertical and moment load is evaluated by displacement-controlled method.Moreover, by parametric computation and comparative analysis the ultimate bearing capacity of mono-pile foundation for offshore wind turbines is evaluated for different diameter. With the increasing of diameter,the ultimate bearing capacity of mono-pile foundation for offshore wind turbines increases.With the increasing of modulus of peripheral soil,the ultimate vertical bearing capacity of mono-pile foundation for offshore wind turbines increases,not obviously,and the ultimate horizontal bearing capacity increases significantly.With the increasing of modulus of end soil,the ultimate vertical bearing capacity of mono-pile foundation for offshore wind turbines increases obviously,however,the ultimate horizontal bearing capacity is not affected.2.The ultimate bearing capacity envelopes of mono-pile foundation for offshore wind turbines are searched by fixed displacement radio procedure and load-displacement controlling procedure.Furthermore,the bearing capacity of mono-pile foundation for offshore wind turbines under combined loading mode is developed.According to finite element analysis,for the different diameters of pile the ultimate bearing capacity envelopes of mono-pile foundation for offshore wind turbines are similar,but the dimension may change.For the different moment component,the ultimate bearing capacity envelopes are similar.With the increasing of moment component,the ultimate bearing capacity envelopes reduce.When moment component is zero,the ultimate bearing capacity envelopes reduce a point.3.Based on studying the bearing behavior of triple-piles foundation and quadruple-piles foundation for offshore wind turbines,the effection of distance between piles and diameter of pile on multi-pile foundations investigated.What's more,according to the engineering data of the proposed Hangzhou Bay wind farm, based on the analyzed bearing capacity behavior of pile foundation for offshore wind turbines,the foundation for offshore wind turbines is analyzed and defined,and the response under earthquake is studied.