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

海上风力发电场通常包括固定基础结构阵列，由嵌入沙子或粘土的桩基支撑。未来计划在欧洲沿海水域开发的项目包括基岩靠近海床表面的地方。在这些地点，采用钻孔和灌浆的方式安装桩基。对于深水地点，未来的发展将涉及浮动海上风力系统；浮式风力发电系统通常需要锚将系统固定在海床上。最近在欧洲水域开发的许多海上风力发电场都是在土壤（沙子和/或粘土）适合用冲击法安装桩基的地方开发的。在过去十年左右的时间里，在这类场地的基础设计和安装方面积累了相当多的经验。在基岩靠近海床表面的地点，有关地基/锚碇设计的累积知识要少得多；因此，这类地点往往被认为相对没有吸引力。因此，需要新的设计程序来促进海上风力发电进一步扩展到需要在岩石中安装地基/锚的地点。目前的项目将直接有助于满足这一需求。海上风力发电机结构的基础和锚的设计需要解决一系列的设计案例。需要采取措施确保基础/锚系统的刚度在适当的范围内，以确保整体结构的动力性能是足够的。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的疲劳失效风险，并确保累积的基础变形（由于盛行的风和波条件）保持在规定的范围内。当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三维有限元模型。研究将进行适当的本构模型，以表示岩石和浆液的行为。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较长的运行时间。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。1D模型将使用有限数量的更详细的有限元分析进行校准。最初的工作将侧重于单调加载，但项目也可能考虑循环加载的影响。该项目属于EPSRC的“地面工程”和“结构工程”研究领域。这项研究也与“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).