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

吸力桶是一种有前途的替代打入桩作为海上风能转换器的基础元件。对于具有三个或四个铲斗的多脚基础，循环拉伸载荷在铲斗尺寸中是设计驱动的。然而，在抗拉强度的预测方面存在重大的知识缺口。这里的具体问题是在装载期间铲斗内部发生的吸入压力的估计，其取决于装载速率和持续时间、土壤渗透性和铲斗几何形状。目前，还不存在允许考虑该吸入压力的适用设计概念。然而，忽视吸力会大大降低桶形基础的经济和生态优势。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承载行为。然而，相应的文献综述表明，相当大的不足之处，在理解的基本现象和数量和质量的实验研究进行到目前为止。因此，在研究项目中应进行模型试验，为进一步数值模拟的充分验证奠定基础。恒定加载速率试验，快速增加，然后恒定载荷和循环载荷试验。应使用经验证的数值模型对不同系统和荷载条件进行详细的参数研究。根据这些结果，应制定一种设计方法，用于估算在任意土壤和荷载条件下吸力桶的抗拉强度。

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.