基于现场试桩的海上风电单桩基础水平承载变形特性研究

Study on Horizontal Load-Bearing and Deformation Performances of Monopile Foundations for Offshore Wind Turbines Based on In-Situ Static Load Tests

海上风电单桩基础的水平承载变形特性直接影响整体结构和风机运行的稳定性和安全性。为研究海上风电大直径单桩基础水平承载变形特性,基于某海上大直径单桩的现场试桩试验结果,采用有限元数值仿真法对桩-土接触面模型、岩土参数选取、桩身水平位移与弯矩变化特征进行分析,并与美国API RP 2A-WSD标准建议的p-y曲线法进行对比。结果表明:在各级荷载作用下,有限元数值仿真结果与试桩实测数据表现出较好的一致性。当采用p-y曲线法计算时,随着水平荷载的增大,桩身水平位移与实测值的误差随水平荷载的增大而增大,在设计上是偏于保守的;同时,桩身变形逐渐增大,最大弯矩点呈下移趋势,反弯点在泥面以下14~16 m,地基土变形由地表逐步向深部延伸,塑性区范围由浅表向深部不断扩大,说明采用的桩-土接触面模型与选取的岩土参数是基本合理的,验证了有限元数值仿真的合理性和有效性。

The horizontal bearing capacity and deformation characteristics for monopile foundations of offshore wind turbines directly influenced the stability and safety of the whole structure and wind turbine operation.In order to study the horizontal bearing capacity and deformation characteristics of monopile foundations,finite element numerical simulations were used to analyze the pile-soil contact model,soil parameters and variable characteristics of horizontal displacement and bending moment of piles based on the in-situ static load tests of single piles.Moreover,the method of the p-y curve recommended by the specification of API RP 2A-WSD was applied to compare the numerical simulation results with that from in-situ tests.It indicated that the simulation results were in good agreement with the measured data from in-situ tests at different load levels.The errors between the horizontal displacement of piles by the p-y curve method and in-situ tests increased with the increase of horizontal loads,which indicated that the p-y curve method was conservative.With the increase of horizontal loads,the horizontal deformation of piles gradually increased,the maximum bending moment points tended to move down,and the reverse bending point was about 14 m to16 m below the mud surface.The deformation and plastic zone of foundation soil gradually extended from the surface to the deep.Therefore,the model of pile-soil interfaces and the selection of geotechnical parameters were basically reasonable,and the rationality and effectiveness of finite element numerical simulations were verified.