Design of Foundations and Anchors in Rock for Offshore Wind Energy Systems

海上风电场通常包括由嵌入沙子或粘土中的桩基支撑的固定基础结构阵列。欧洲沿海沃茨未来计划的开发包括基岩接近海底表面的地点。在这些地点，桩基础通过钻孔和灌浆安装。对于深水场地，未来的发展涉及浮动海上风力系统;浮动风力系统通常需要锚将系统系泊到海床上。最近在欧洲沃茨开发的海上风电场大多利用土壤（沙子和/或粘土）适合通过冲击法安装桩基的场地。在过去十多年，我们在这类地盘的地基设计和安装方面，已累积了相当多的经验。对于基岩接近海底表面的场地，在基础/锚的设计方面积累的知识要少得多;因此，这类场地往往被认为是相对没有吸引力的。因此，需要新的设计程序，以促进海上风力发电的进一步扩展到需要在岩石中安装基础/锚的地点。目前的项目将直接满足这一需求。海上风力涡轮机结构的基础和锚的设计需要解决一系列的设计案例。需要程序来确保基础/锚系统的刚度处于适当的范围内，以确保整个结构的动态性能是足够的。还必须确保基础/锚的强度足以承受可预见的风暴荷载条件。需要考虑钢支撑结构内疲劳失效的风险，并确保累积的基础变形（由于盛行风和波浪条件）保持在规定的范围内。目前的项目将提供设计程序，以支持满足这些设计约束的结构和基础规范。在研究的初始阶段，该项目将涉及开发嵌入岩石中的锚和桩的性能的三维有限元模型。将对代表岩石和灌浆特性的适当本构模型进行研究。对于实际设计活动，三维有限元分析的缺点是计算通常需要很长的运行时间。因此，将开发新的替代设计模型，以促进快速设计计算。这些模型将基于一维（1D）有限元框架，其中桩或锚被建模为嵌入梁。将使用有限数量的更详细的有限元分析来校准1D模型。初期的工作将集中在单调加载，但该项目也可能考虑循环加载的影响。该项目福尔斯EPSRC的“地基工程”和“结构工程”的研究领域。该研究也与“风力发电”研究领域有关。该项目正在与Geowynd（一家专业工程咨询公司）合作进行。

Offshore wind farms typically comprise arrays of fixed-base structures supported by piled foundations embedded in sand or clay soils. Future planned developments in European coastal waters include sites where the bedrock is close to the seabed surface. At such sites, piled foundations are installed by drilling and grouting. For deep water sites, future developments involving floating offshore wind systems are envisaged; floating wind systems typically require anchors to moor the system to the seabed.Much of the recent offshore wind farm development in European waters has exploited sites where the soils (sand and/or clay) are suitable for piled foundations to be installed by percussion methods. Over the last decade or so, considerable experience has been accumulated on the design and installation of foundations for sites of this type. There is much less accumulated knowledge on the design of foundations/anchors for sites where the bedrock is close to the seabed surface; such sites are therefore often considered to be relatively unattractive. New design procedures are therefore needed to facilitate the further expansion of offshore wind generation to sites where installation of foundations/anchors into rock is required. The current project will contribute directly to this need.The design of foundations and anchors for offshore wind turbine structures requires a range of design cases to be addressed. Procedures are needed to ensure that the stiffness of the foundation/anchor system lies within appropriate bounds to ensure that the dynamic performance of the overall structure is adequate. It is also necessary to ensure that the strength of the foundation/anchor is sufficient to withstand foreseeable storm loading conditions. Considerations are needed on the risk of fatigue failures within the steel supporting structure and on ensuring that accumulated foundation deformations (due to prevailing wind and wave conditions) are kept within defined bounds. The current project will deliver design procedures that will support the specification of structures and foundations that satisfy these design constraints. In the initial stages of the research the project will involve the development of 3D finite element models of the performance of anchors and piles embedded in rock. Studies will be conducted on appropriate constitutive models to represent the behaviour of the rock and grout. For practical design activities, 3D finite element analysis has the disadvantage that the calculations often require lengthy run times. New alternative design models will therefore be developed that facilitate rapid design calculations. These models will be based on a one dimensional (1D) finite element framework in which the pile or anchor is modelled as an embedded beam. The 1D model will be calibrated using a limited number of more detailed finite element analyses. Initial work will focus on monotonic loading, but the project may also consider cyclic loading effects.This project falls within the EPSRC 'ground engineering' and 'structural engineering' research areas. The research is also related to the 'wind power' research area.The project is being conducted in collaboration with Geowynd (a specialist engineering consultancy).