Pile foundations for offshore structures are subjected to vertical–horizontal load combinations. The current design method separately analyses horizontal and vertical responses of piles without considerations of the combined effect of the loads on soil–pile interaction. However, there is experimental and numerical evidence that lateral behaviour of a pile–soil system can be affected by both axial compression and tension load on the pile. In this study, two single-pile and two tripod-pile centrifuge model tests under different loading conditions were analysed to investigate the influence of combined loads on the lateral response of the soil–pile system. The displacement and the bending moment were measured and analysed to highlight the behaviour of the pile–soil system under different loading conditions. The p–y (resistance–deflection) curves for the different tests were calculated and compared to reveal the influence of the axial load component on the lateral behaviour of soil–pile systems. It is concluded that compared with pure lateral loading, the p–y curves of piles under compression are steeper due to the soil densification effect, while the opposite is observed under tension load – that is, the p–y curves are gentler.

中文翻译：

---

砂中桩垂直-水平静载p-y曲线的离心研究

海上结构的桩基础承受垂直-水平荷载组合。当前的设计方法单独分析桩的水平和垂直响应，而没有考虑荷载对土桩相互作用的综合影响。然而，有实验和数值证据表明，桩土系统的横向行为会受到桩上的轴向压缩和拉伸载荷的影响。本研究通过分析不同荷载条件下的两个单桩和两个三角桩离心模型试验，研究复合荷载对土-桩系统横向响应的影响。对位移和弯矩进行测量和分析，以突出桩土系统在不同载荷条件下的行为。在对ÿ计算并比较了不同试验的（阻力-挠度）曲线，以揭示轴向载荷分量对土桩系统横向行为的影响。得出的结论是，与纯侧向荷载相比，由于土壤致密化效应，受压桩的p-y曲线更陡峭，而在拉伸荷载下观察到相反的情况，即p-y曲线更平缓。