With the offshore wind industry rapidly expanding worldwide, geotechnical research is being devoted to foundation optimisation – most intensively for large-diameter monopiles. The analysis and design of monopiles still suffers from significant uncertainties in relation to cyclic/dynamic loading conditions. The aim of this work is to shed new light on dynamic soil–monopile interaction, based on the results of unique full-scale experiments performed at the Westermeerwind wind park (Netherlands). The response of a 24 m long, 5 m diameter monopile to harmonic lateral loading of varying amplitude and frequency is inspected. The analysis of original field measurements (soil accelerations and pore pressures) enables the lateral stiffness observed at the monopile head to be linked to dynamic effects occurring in the surrounding soil. The interpretation of measured data is supported by three-dimensional finite-element studies, also looking at the influence of drainage conditions and monopile size. The set of results presented supports the need for dynamics-based monopile design, as higher frequencies gain relevance in the most recent offshore wind developments.

中文翻译：

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沙子中单桩动态横向刚度的频率效应：来自现场测试和 3D 有限元建模的见解

随着海上风电行业在全球范围内迅速扩张，岩土工程研究正致力于地基优化——最集中的是大直径单桩。单桩的分析和设计仍然存在与循环/动态载荷条件相关的重大不确定性。这项工作的目的是根据在 Westermeerwind 风电场（荷兰）进行的独特的全面实验的结果，揭示动态土壤 - 单桩相互作用的新思路。检查了 24 m 长、5 m 直径的单桩对不同幅度和频率的谐波横向载荷的响应。对原始现场测量（土壤加速度和孔隙压力）的分析使在单桩头处观察到的横向刚度与周围土壤中发生的动态效应相关联。测量数据的解释得到了三维有限元研究的支持，还研究了排水条件和单桩尺寸的影响。所呈现的一组结果支持基于动力学的单桩设计的需要，因为更高的频率在最近的海上风电开发中获得了相关性。