软粘土地基中多向水平循环荷载作用下单桩的承载力弱化和变形机理研究

Large diameter monopiles are always used as a foundation of wind turbines. Besides the dead loads, these piles are subjected to lateral cyclic loads such as, wind load, wave load and ocean current load, from different directions. Degradation of stiffness and strength will occur in soft clay surrounding the pile under cyclic loading, resulting in large pile foundation deformation and even leading to bearing capacity failure .Large number of circle static and dynamic tests considering the cyclic principal stress rotation and complex stress path will be carried out in this program by using GDS dynamic hollow cylinder apparatus, and dynamic property of the soft clay under cyclic loading is obtained. Elastic-plastic constitutive model of soft clay will be established with principal stress rotation taken into account. Pile foundation under multi-directional horizontal cyclic loading in soft clay is analyzed with Elastic-Plastic finite element method. The Laboratory Model Tests and full scale model tests will be carried out for pile foundation under multi-directional horizontal cyclic loading in soft clay, and provide modification suggestion for the finite element model. The theoretical basis for the design of pile foundation controlled by displacement under multi-directional horizontal cyclic loading is provided by finite element analysis. Abundant academic content and great engineering application value in this project provide reliable theoretical guidance and technical support for the foundation design of wind turbines.

海上风机对变形要求高且往往采用大直径单桩基础。这些桩基除了承受自重荷载外还要承受来自不同方向的风、波浪、洋流等水平循环荷载。在这些荷载作用下，桩周土会发生循环软化，导致桩基变形过大，发生承载失效。本项目利用GDS空心圆柱扭剪仪对软粘土试样进行大次数考虑主应力轴方向循环变化的复杂应力路径下的静、动力试验，获得软粘土在大次数循环荷载作用下的静动力特性；通过动力试验结果，综合考虑主应力轴旋转条件下的屈服面、流动法则和硬化规律特性；通过自编弹塑性有限元程序，分析软粘土地基中多向水平循环受荷桩的变形；进行软粘土地基中多向水平循环荷载作用下桩基的室内模型试验研究和原位试验研究，并对有限元分析模型进行修正。通过参数分析为位移控制的多向水平循环荷载作用下桩的设计方法提供理论依据。本项目的研究既具有丰富的学术内涵，又有重大的工程应用价值，可为海上风机桩基设计提供可靠的理论指导和技术支持。

海上风机对变形要求高且往往采用大直径单桩基础。这些桩基除了承受自重荷载外还要承受来自不同方向的风、波浪、洋流等水平循环荷载。在这些荷载作用下，桩周土会发生循环软化，导致桩基变形过大，发生承载失效。本项目利用GDS空心圆柱扭剪仪对软粘土试样进行大次数考虑主应力轴方向循环变化的复杂应力路径下的静、动力试验，获得软粘土在大次数循环荷载作用下的静动力特性；通过动力试验结果，综合考虑主应力轴旋转条件下的屈服面、流动法则和硬化规律特性；通过自编弹塑性有限元程序，分析软粘土地基中多向水平循环受荷桩的变形；进行软粘土地基中多向水平循环荷载作用下桩基的室内模型试验研究和原位试验研究，并对有限元分析模型进行修正。通过参数分析为位移控制的多向水平循环荷载作用下桩的设计方法提供了理论依据。本项目的研究具有丰富的学术内涵和重大的工程应用价值，为海上风机桩基设计提供可靠的理论指导和技术支持。