Bearing behavior of suction bucket foundations under tensile loading in non-cohesive soils

抽吸斗是一种很有前途的替代打桩作为基础元件的海上风能转换器。对于三桶或四桶的多吊舱基础，循环拉荷载在桶的尺寸上进行设计驱动。然而，关于拉伸阻力的预测存在显著的知识差距。本文的具体问题是加载过程中桶内吸力压力的估计，这取决于加载速率和加载时间、土壤渗透性和桶的几何形状。目前，没有适用的设计概念允许考虑这种吸入压力。然而，忽略吸力会大大降低桶形基础的经济效益和生态效益。申请人开发了一个数值模型，可以根据上述影响参数确定拉伸轴承的行为。然而，相应的文献综述表明，迄今为止，在对基本现象的理解和开展的实验研究的数量和质量方面存在相当大的不足。因此，本研究项目应进行模型试验，为进一步数值模拟的充分验证奠定基础。预计将进行恒定加载速率试验，然后快速增加恒定加载速率和循环加载速率试验。对不同的系统和载荷条件进行详细的参数研究，应使用经过验证的数值模型。在此基础上，提出了一种估算任意土体和荷载条件下吸力斗抗拉性能的设计方法。

Suction Buckets are a promising alternative to driven piles as foundation elements for offshore wind energy converters. For multipod foundations with three or four buckets the cyclic tension load is design-driving in the dimensioning of the buckets. However, significant knowledge gaps exist regarding the prediction of the tensile resistance. The specific problem herein is the estimation of the suction pressure occurring inside the bucket during loading, which is dependent on loading rate and duration, soil permeability and bucket geometry. At the time being, no applicable design concept exists which allows consideration of this suction pressure. However, neglecting the suction considerably reduces the economic and ecologic advantages of the bucket foundation.The applicant developed a numerical model which enables the determination of the tensile bearing behavior dependent on the mentioned influence parameters. However, the corresponding literature review showed considerable deficiencies in the understanding of the basic phenomena and in number and quality of the experimental investigations carried out so far. Therefore, model tests shall be carried out in the research project, which shall form a basis for a sufficient validation of further numerical simulations. Tests with constant loading rates, with rapidly increased and then constant load and cyclic loading tests are foreseen. Detailed parametric studies for different system and loading conditions shall be carried out with the validated numerical models. Based on the results, a design method for the estimation of the tensile resistance of a suction bucket under arbitrary soil and loading conditions shall be developed.