In order to perform optimised and safe design of foundations for offshore wind turbines (OWT), it is important to have calculation tools that describe the key features of water-saturated soil subjected to complex and irregular loading over a wide range of strain levels. Soils subjected to cyclic loading are prone to strain accumulation. The accumulated (plastic) volumetric strain may result in excess pore pressure or stress relaxation, which will reduce the effective stresses, stiffness and strength of the material. Strain accumulation in dense sand is a complex mechanism of deformation and it is challenging to describe it properly. Four different soil models to describe the stress–strain relationships of dense sand are evaluated in this paper: two implicit models that follow the actual stress history and two explicit models that calculate the accumulated strains as a function of number of cycles. These models are first evaluated on the basis of their theoretical framework and back-calculations of laboratory tests specifically carried out for the design of OWT foundations in dense sand. Second, the models are implemented in finite-element analyses and evaluated on the basis of the analyses of an OWT monopile subjected to different loading conditions.

中文翻译：

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土质模型在密沙中改善海上风力发电机基础的设计评估

为了对海上风力涡轮机（OWT）的基础进行优化和安全的设计，重要的是要有计算工具来描述饱和水饱和土在各种应变水平上承受复杂和不规则载荷的关键特征。承受周期性载荷的土壤易于应变累积。累积的（塑性）体积应变可能会导致孔隙压力过大或应力松弛，从而降低材料的有效应力，刚度和强度。致密砂土中的应变积累是变形的复杂机制，要对其进行恰当的描述具有挑战性。本文评估了四种不同的描述致密砂土应力-应变关系的土壤模型：遵循实际应力历史的两个隐式模型和计算累积应力随循环次数变化的两个显式模型。这些模型首先根据其理论框架和专门为密砂中OWT基础设计而进行的实验室测试的反计算进行评估。其次，该模型在有限元分析中实施，并在承受不同载荷条件的OWT单桩分析的基础上进行了评估。