一种可以描述桩端位移累积的新型Q-z模型

海上风电属变形敏感结构,而导管架基础海上风电结构在服役期内下部桩基础会承受较大竖向循环荷载。在竖向受荷桩基的分析与计算中,采用ABAQUS分析桩端影响区域,依据动三轴实验中砂土的应变累积特性,提出一种新型Q-z模型。与传统Q-z模型比较,该模型能通过不同参数取值,模拟在轴向循环荷载下桩端的位移累积。结合有限元软件COMSOL进行二次开发,模拟单桩轴向循环加载工况,与离心机实验进行对比,验证了该Q-z模型的合理性。在数值计算中分别采用美国石油学会（API）规范系列桩土相互作用模型（p-y）、可考虑桩-土界面强度和刚度循环弱化效应的弹塑性t-z模型,可描述桩端位移累积的新型Q-z模型,分析海上升压站在循环荷载下的响应规律,为海上升压站设计提供相应的建议。

A NOVEL Q-z MODEL TO DESCRIBE PILE TIP ACCUMULATED DISPLACEMENT

Offshore wind power is a deformation-sensitive structure, and the jacket foundation offshore wind power structure will bear large vertical cyclic loads during its service period. For analyzing and calculating the vertical load of the pile foundation, ABAQUS is used to analyze the influence zone of the pile tip. Based on the strain accumulation characteristics of sand in dynamic triaxial test, a novel Q-z model is proposed. Compared with traditional Q-z model, this novel model can use several parameters to simulate the behavior of displacement accumulating at the pile tip under axial cyclic loadings. Combined with the finite element software COMSOL, the secondary development is carried out to simulate the axial cyclic loading condition of single piles. The model validation is conducted with centrifuge tests of single pile under axial cyclic loadings. In the numerical simulation, the pile-soil interaction model (p-y) in the American Petroleum Institute （API） standard, the elastoplastic t-z model that considers the cyclic degradation of strength and stiffness in the pile-soil interface, and the novel Q-z model which can describe the pile tip accumulated displacement is adopted respectively to analyze the responses of offshore substation under cyclic loadings, which provide useful suggestions for the design of offshore substation.