The Uncertain Parametric Study Of The Lateral Bearing Capacity Of Offshore Wind Turbine Single Pile Foundations

During the era of resource shortage,countries have attached importance to the offshore wind energy for its green healthy and sustainable development.In various pile foundations,the single pile foundation is widely used in the support structure of the wind turbine because of its advantages of simple,convenient and quick manufacture.Compared with the terrestrial wind power pile foundation,the offshore wind power pile foundation is not only affected by the axial self-weight load,but also by the horizontal wind load.The most popular horizontal load pile calculation method today is the p-y curve method.The complexity of geotechnical engineering and the exploration of seabed soil lead to the uncertainty of soil parameters.Therefore,it is necessary to introduce the uncertainty analysis method to study the failure probability of pile foundation.In response to these problems,this thesis mainly carried out the following work:1.In this thesis,the p-y curve theories of many scholars are analyzed,and coded with Matlab.By comparing and analyzing the calculation results of each p-y theory,it is found that the calculated values obtained by the p-y theory adopted by the API specification are the closest to the measured values of the engineering.The calculation results of each theory show that the calculated results are slightly larger than the measured values.Within the length of one-third of the pile-soil interaction range,the depth of the maximum bending moment in each theory is slightly larger than the measured depth.The results of various theoretical calculations show that the calculated displacement'difference is slightly larger than the bending moment's.Then,the single factor sensitivity analysis of each parameter is carried out,and the parameters with great influence on the internal force of the pile foundation are selected as the research parameters of the subsequent reliability analysis.2.The finite element model of the project is established by using Plaxis 3D.The calculation results show that the horizontal displacement result of Plaxis 3D numerical simulation is slightly larger than the measured value,and the bending moment calculation result is slightly smaller than the measured value.Therefore,if the bending moment is selected as the function parameter of the pile foundation failure,the calculation result is dangerous for the actual engineering.The range that horizontal force can have effect on is only within one-third of the depth of the pile;The maximum bending moment depth of the pile is smaller than the measured depth;the horizontal bending forces of different sizes have the same depth of the maximum bending moment.After the above finite element deterministic analysis,the single factor sensitivity analysis of each parameter is carried out,and the parameters with great influence on the internal force of the pile foundation are selected as the research parameters of the subsequent reliability analysis.3.The Monte Carlo method was used to analyze the pile foundation reliability of the p-y curve model and the Plaxis 3D finite element model.Then,the effects of the horizontal force and the mean,variation coefficient and distribution type of the distribution function of some parameters on the failure probability of pile foundation are discussed respectively.It is found that the uncertainty of horizontal force has a greater impact on the failure probability of pile foundation.In addition,the uncertainty of the mean of the parameters has a greater influence on the failure probability of the pile than that of the coefficient of variation.And the failure probability of pile foundation is also sensitive to the selection of parameter distribution type.Finally,some suggestions for the selection of the mean,coefficient of variation and distribution function of each parameter are provided.