基于荷载传递曲线的大直径钢管桩水平受力特性分析方法

An analytical method for laterally loaded large-diameter steel pipe piles based on load-transfer curves

海上风电通常选用大直径钢管单桩基础。水平受力的大直径钢管桩桩截面转动引起的桩周土对桩的附加抗力作用较为显著,为考虑这部分附加抗力对大直径桩水平受力特性的影响,首先,提出适用于大直径钢管桩水平受力分析的修正文克勒地基梁模型,分别使用非线性弹簧模拟土和考虑剪切变形的C1型梁单元代表桩,假定桩单元内部土荷载传递曲线的割线刚度为线性分布,推导相应的有限元公式,形成考虑桩截面转动附加抗力作用的耦合法,并根据该算法编制程序。然后,基于现有的土荷载传递曲线使用耦合法对算例进行分析,以验证耦合法的合理性,并将其计算结果与仅考虑横向非线性弹簧作用的p-y法的计算结果进行对比分析。分析结果表明:耦合法可更好地预测大直径钢管桩的水平受力特性;大直径钢管桩桩身变形越接近于刚性转动,桩截面转动产生的附加土抗力作用越显著,当大直径钢管桩桩身变形接近于柔性变形时,桩截面转动产生的附加土抗力作用基本可以忽略。

Offshore turbines are often supported on large-diameter steel pipe monopoles. There is a significant effect of soil-added-resistance force caused by the rotation of the pile section of laterally loaded large-diameter steel pipe piles. The impact of the soil-added-resistance force on pile lateral capacity should be taken into account. A modified Winkler foundation beam model was proposed to model the lateral bearing loads of large-diameter steel pipe piles,in which the soil and the pile are respectively modeled by nonlinear springs and C1 beam elements considering the shear deformation. Assuming that the secant stiffness of the soil load transfer curves inside a pile element is linear,finite element formulas were deduced to develop a coupling method which can take into account the soil-added-resistance force caused by the rotation of the pile section,and a corresponding program was written. Two case studies were performed to verify the coupling method developed in this paper,and their computed results were compared with those obtained by the p-y method only considering the lateral nonlinear springs′ effect. The results show that the coupling method can better predict the laterally loaded characteristics of the large-diameter steel pipe pile. The closer the deformation of the large-diameter steel monopile is to the rigid rotation,the more obvious the soil-added-resistance force caused by the rotation of the pile section. On the contrary,the soil-added-resistance force can be ignored while the deformation of the large-diameter steel pipe pile is close to the flexible deformation.