Bucket foundations have been increasingly used to support offshore wind turbines as alternatives to monopiles and can be classified into two types: monopod and tripod/jacket supported on multiple shallow foundations. Despite the recent research on the bearing capacity and stiffness of skirted foundations, knowledge regarding the monotonic and cyclic responses of multiple bucket foundation systems in saturated sand is scarce.

In this study, the angular rotation of mono-bucket and tripod foundation systems in dense sand due to drained monotonic and cyclic loading was analyzed by performing a series of three-dimensional finite element (FE) analyses. The Hardening Soil Model with Small Strain Stiffness (HS small) and the UBC3D-PLM soil model were employed to analyze the moment response of offshore foundations subjected to wind and wave loading.

The procedures were validated against a database of well-documented centrifuge tests. Calibration was carried out based on the monotonic and cyclic model tests, in-situ shear wave velocity measurements, and empirical relationships for shear moduli. Long-term deformations and the resulting decreasing trend in accumulated rotation, which is a unique feature of tripod suction caisson foundations (the so-called “self-healing’’ mechanism), uncertainties, and nonlinearities in centrifuge tests and numerical predictions involving different alternative calibration scenarios of the models are discussed. Based on the numerical results, a closed-form expression is proposed that enables the prediction of drained bearing capacity of multiple caissons under combined loading. This expression was validated for a range of embedment ratios.

斗式基础越来越多地用于支撑海上风力涡轮机，作为单桩的替代品，可分为两种类型：单脚架和支撑在多个浅基础上的三脚架/护套。尽管最近对裙边基础的承载力和刚度进行了研究，但关于饱和砂土中多桶基础系统的单调和循环响应的知识很少。

在这项研究中，通过执行一系列三维有限元 (FE) 分析，分析了由于排水单调和循环加载而导致的密砂中单桶和三脚架基础系统的角旋转。采用小应变刚度（HS small）硬化土壤模型和UBC3D-PLM土壤模型分析海上地基在风浪载荷作用下的弯矩响应。

这些程序根据记录良好的离心机测试数据库进行了验证。校准基于单调和循环模型测试，原位剪切波速度测量和剪切模量的经验关系。长期变形和由此产生的累积旋转减少趋势，这是三脚架吸力沉箱基础的独特特征（所谓的“自愈”机制）、离心机测试中的不确定性和非线性以及涉及不同替代方案的数值预测讨论了模型的校准场景。基于数值结果，提出了一个封闭式表达式，可以预测组合载荷下多个沉箱的排水承载力。该表达式已针对一系列嵌入比率进行了验证。