Behaviour of Suction Bucket Foundations for Offshore Wind Energy Converters under Cyclic Loading

吸水桶是海上风能转换器的另一种基础类型。由于它们被广泛证明是无噪音的安装，它们可以用来代替通常的打入桩的海上基础。在吸力桶形基础的设计中，风、水波作用下的循环荷载起着特殊的作用。这些荷载可能会导致地基性能发生变化。由于缺乏循环响应的经验，需要进行广泛的研究来确保吸力桶基础在其计划的使用年限内的稳定性。因此，建议的研究项目的主题是对吸力桶形基础进行数值和试验研究，以定量确定其在循环荷载作用下的性态变化。在有限元分析的框架内，将研究吸力桶在轴向和横向循环荷载作用下的响应，其中考虑了饱和土体中永久变形和超孔压的累积。因此，饱和砂土的模拟将采用完全耦合两相模型和亚塑性本构模型相结合的方法。在模型试验中，将研究在循环轴向和水平荷载作用下地基响应的长期变化。调查应能得出重要的结论，利用这些发现可以可靠地确定循环动态载荷对吸斗性能的影响。在这些结果的基础上，提出了一种估计循环载荷下吸斗的位移和转角的设计方法。因此，可以经济地确定承受循环负载的吸力桶的尺寸，并显著提高海上风能转换器的运行可靠性。

Suction buckets are an alternative type of foundation for offshore wind energy converters. Due to their widely proved noise-emission-free installation, they can be used instead of the usual offshore foundations with driven piles. Cyclic loads, induced by wind and water waves, play a special role in the design of suction bucket foundations. These loads can lead to changes in foundation behaviour. Due to lack of experience on cyclic response, extensive studies are required to ensure the stability of suction bucket foundations throughout their planned service-life time. Therefore, the subject of the proposed research project is the numerical and experimental investigation of the suction bucket foundations in order to quantitatively determine the changes in their behaviour caused by the cyclic loads. In the framework of the finite element analyses, the response of suction buckets subjected to cyclic axial and lateral loads will be investigated, taking into account the accumulation of permanent soil deformations and excess pore water pressures in saturated soil. Therefore, a fully coupled two-phase model combined with a hypoplastic constitutive model will be used for the modelling of the saturated sandy soil. In the model test, the long-term changes in foundation response, which are induced by cyclic axial and lateral loads, will be studied. The investigations should lead to important findings with which the effects of cyclic-dynamic loadings on the behaviour of suction buckets can be reliably determined. Based on these results, a design method for the estimation of the displacements and rotations of cyclic loaded suction buckets will be developed. Thus, an economic dimensioning of suction buckets subjected to cyclic loads, as well as a significant increase in the operational reliability of offshore wind energy converters can be achieved.