多向耦合荷载下滩涂风电基础承载特性三自由度模型试验与理论研究

Considering the lack of research on foundations for wind turbines in coastal area under multi-directional loads which is urgently required for constructions of wind tubines in coastal area, a three degree-of-freedom loading device is developed to conduct model tests for foundations under multi-directional loads. Influences of couple effects of loads on bearing mechanics of foundations for wind turbines in costal area is studied throuhg model tests. Considering the couple effect of loads and pile-soil interactions, an eleatic analytical method is developed to analyze wind turbine founations in coastal area under multi-directional loads based on the model tests.Introducing non-linear pile-soil interactions which can consider the couple effect of the loads and ultimate resistances of soils into the method, a non-linear method is developed to analyze the foundations for wind turbines in coastal area under multi-directional loads. The method is verified through comparison with results from a 3D no-linear finite element method and results from model tests. Combined with limit analysis theory, a three-dimentional yeild surface for wind turbine in coastal area foundations under multi-directional loads which can consider the couple effect of the load components and non-linear interactions between piles and soils is developed for further study of bearing capacity of foundations for wind turbines in coastal area.

结合临海滩涂风电场建设的迫切需求，针对多向耦合荷载作用下滩涂软弱地基上风电基础承载特性研究存在的不足，本课题首先研发一套能够进行三向耦合加载的大尺寸多自由度基础加载设备，进而通过大尺寸多自由度基础加载模型试验，揭示多向耦合荷载对临海滩涂风电基础力学特性的影响规律。基于模型试验结果，考虑多向荷载耦合作用及桩-井-土相互作用，提出滩涂风电基础的受力特性混合分析方法。引入可以考虑多向荷载耦合作用的桩土非线性模型和土体极限抗力，建立滩涂风电基础的承载特性非线性分析方法，并与三维弹塑性有限元计算结果和试验结果进行对比验证。结合极限分析理论建立考虑多向荷载耦合作用的风电基础承载能力的三维包络图，从而为滩涂软弱地基风电基础承载特性的合理评估提供理论基础。

依据临海滩涂风电场建设的迫切需求，本课题首先对滩涂风电基础的形式进行了调研分析，得到具备应用潜质的基础形式—梁板式桩筏基础和大直径单桩基础，并围绕该两种基础形式展开研究。针对多向耦合荷载作用下滩涂软弱地基上风电基础承载特性研究存在的不足的问题，本课题首先研发了一套高精度的能够进行三向耦合加载的多自由度基础加载设备。进而通过梁板式基础大型室内模型试验、多向荷载下梁板式桩筏基础小型模型试验、梁板式桩筏基础现场测试、多向荷载下大直径单桩室内模型试验等一系列试验，揭示了多向耦合荷载对临海滩涂风电基础承载特性的影响机理。试验表明，砂土中竖向荷载存在有利于提高风机基础的水平承载能力，且对于梁板式桩筏基础，竖向荷载对基础承载力的提高主要表现为改变了桩土荷载分担比，而对于大直径单桩竖向荷载对其水平承载性能的影响主要由三部分组成，最终影响取决于该三部分的组合。承台的刚度、埋深对梁板式基础的承载性能均具有重要的影响。在试验的基础上，对多向荷载作用下的风机基础进行了数值模拟，分析了风机承载性能的影响因素，分析了桩土相互作用。分析表明风机基础的埋深增加、上覆荷载增加可有效提高其水平承载性能，基础的水平承载能力随竖向荷载的增加线性增加。在竖向荷载作用下，竖向桩土相互作用增强的同时，水平桩土相互作用也明显增强，并建立了大直径桩p-y曲线的提取方法。总结试验和有限元模拟结果，首先基于弹性层状理论，全面考虑桩-土-筏相互作用，建立分层地基中多向荷载作用下弹性桩筏基础分析方法。在此基础上，引入非线性的桩土相互作用和厚板理论来模拟梁板式筏板，并考虑筏板与周边土体的相互作用来模拟埋深的影响，建立了分层地基中多向荷载作用下梁板式桩筏基础非线性分析方法。通过与试验和有限元结果的对比验证了该方法的正确性。最终尝试通过总结前述分析结果建立多向荷载下滩涂风电基础的承载力包络图。