Experimental Investigation and Numerical Analysis of the Behaviour of Plate Anchor Foundations Subjected to Cyclic Loading in Sands

EPRSC项目描述试验研究和数值分析的板锚基础的行为受到循环荷载在砂在过去的几十年里，海上风电场已经经历了显着的发展和扩大方面的功率容量和操作区域。虽然大多数海上风力涡轮机（OWT）结构由固定基础（例如，支柱、导管架基础等）支撑，已经研究了更适合于大型OWT和较深沃茨的备选基础类型。具体而言，板锚基础被认为是适用于带系泊系统的浮动OWT的可行且有效的基础类型[1]，[2]。浮动OWT的基础受到上拔荷载和水平荷载的组合作用，这些荷载由作用在OWT结构和系泊缆上的环境荷载引起。由于荷载的循环性质，基础在其使用寿命期间会经历大量的加载-卸载循环[3]。虽然相对有限，一些实验研究已经进行了调查的行为和能力的板锚在循环荷载下。总体而言，研究显示了一致的结果，循环荷载导致粉土[4]和砂土[5]、[6]中地基承载力的增加。虽然已经在理论基础上模拟了粉土地基承载力的变化[4]，但是对砂土中板基础承载力变化的量化方法的分析有限。因此，本研究项目旨在研究砂土中板锚基础在循环荷载作用下的响应。此外，它的目的是建立分析和数值模型，预测循环荷载对地基承载力的影响。考虑到循环荷载引起的强度增益效应，可以为海上应用提供更优化、更经济的基础设计解决方案。该项目福尔斯属于EPSRC“工程”研究领域，在“能源和脱碳”主题的背景下。对于该项目，将进行一系列实验室试验，以研究饱和砂土中板基础模型在加卸载循环下的行为。基础模型将承受不同频率和幅度的循环荷载。将对荷载特性对地基承载力和性能的影响进行分析和量化。基于对循环荷载作用后地基性状的机理分析，提出了一个预测循环荷载作用后地基单调承载力的分析模型。此外，还将进行三维有限元分析，对地基性状进行数值模拟和参数研究。根据参数研究的结果，建议最佳设计参数值，以最大化循环后地基承载力。最后，一个一般的设计框架OWT板基础将新建议，将开发的分析模型，估计后循环单调能力或有限元模型。

EPRSC Project DescriptionExperimental Investigation and Numerical Analysis of the Behaviour of Plate Anchor Foundations Subjected to Cyclic Loading in SandsOver the past several decades, offshore wind farms have been undergoing significant development and expansion in terms of their power capacity and operating regions. While most of the offshore wind turbine (OWT) structures are supported by fixed foundations (e.g. monopile, jacket foundations, etc.), alternative foundation types have been investigated as options that are more suitable to large OWTs and deeper waters. Specifically, plate anchor foundations have been considered a feasible and efficient foundation type for applications in floating OWTs with mooring systems [1], [2].Foundations of floating OWTs are subjected to a combination of uplift and horizontal loads, which are induced by the environmental loads acting on the OWT structure and mooring lines. Due to the cyclic nature of the loads, the foundation is subjected to a significant number of loading-unloading cycles during its service lifetime [3]. Although relatively limited, several experimental studies have been carried out to investigate the behaviour and capacity of plate anchors under cyclic loading. Overall, the studies showed consistent results, where the cyclic loading results in an increase in the foundation capacity in both silt [4] and sands [5], [6]. While the change in the foundation capacity has been simulated on a theoretical basis for silts [4], there has been limited analysis on the methods for quantifying the capacity change of plate foundations in sands.Thus, this research project aims to investigate the response of plate anchor foundations subjected to cyclic loading in sands. In addition, it is aimed to develop analytical and numerical models for predicting the effects of cyclic loading on the foundation capacity. The consideration of the strength gain effects due to cyclic loading would allow for more optimal and economic foundation design solutions for offshore applications. This project falls within the EPSRC "Engineering" research area, within the context of the "Energy and Decarbonisation" theme.For this project, a series of laboratory tests will be carried out to investigate the behaviour of plate foundation models under loading-unloading cycles in saturated sand. The foundation models will be subjected to cyclic loading with different frequencies and magnitudes. The effects of the loading characteristics on the foundation capacity and behaviour will be analysed and quantified. Based on the analysed mechanism behind the foundation behaviour after cyclic loading, an original analytical model will be suggested for the prediction of the post-cyclic monotonic capacity. In addition, three-dimensional finite element analysis (FEA) will be carried out for the numerical simulation and parametric studies on the foundation behaviour. Based on the results of the parametric studies, optimal design parameter values would be suggested for the maximisation of the post-cyclic foundation capacity. Finally, a general design framework for plate foundations of OWTs will be newly suggested by incorporating the developed analytical models for estimating the post-cyclic monotonic capacity or the FEA model.