Interaction between Seabed Soil and Offshore Wind Turbine Foundations
Interaction between Seabed Soil and Offshore Wind Turbine Foundations
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发表时间：
2012
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通讯作者：
Nilas Mandrup Hansen
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作者：
Nilas Mandrup Hansen
今天，单体桩被广泛用作支撑浅水海上风力涡轮机(OWT)的基础。单层膜的刚度是设计的重要方面之一。现场观察显示，一些已经安装在现场的单体电池表现出比目前设计建议预测的更僵硬的行为。本文通过数值模型和试验研究，研究了与单桩刚度有关的桩/海床相互作用问题。数值模型为3D模型。采用有限元软件COMSOL MultiPhysitics计算土体的动力响应。该模型基于Biot固结理论，包括四个方程，前三个方程描述了应力场的平衡条件，第四个方程是所谓的存储方程，描述了孔隙水的质量守恒和达西定律给出的渗流速度(Sumer和Fredsøe，2002，第10章)。模型中考虑的土体本构方程是常见的线性孔弹性土体的应力应变关系。在振冲桩表面采用所谓的无滑移边界条件。通过室内实验对数值模型进行了验证。实验装置包括容器(直径2m、高2.5m的圆形水池)和不锈钢模型桩(直径20 cm)。试验采用粗砂(D50=0.64 mm)。试验中测量了孔隙水压力、桩的位移和桩上的力。利用霍尼韦尔压力传感器，在垂直方向延伸0.75米、径向延伸0.10米的网格上(距离桩边缘最近的测量点在距桩边缘2厘米处)在12个点上测量孔隙水压力。桩的位移是用传统的电位计测量的，力的测量是用拉压S梁式称重传感器测量的。该模型经过验证和测试，用于计算在野外通常遇到的一组条件下的土壤响应。结果以数值模拟得到的无量纲p-y曲线的形式给出。进行了参数研究，观察了各种参数对后者的影响。参数研究表明，对于给定的位移，y，土壤
Today, monopiles are widely used as foundation to support offshore wind turbines (OWT) in shallow waters. The stiffness of monopiles is one of the important design aspects. Field observations show that some monopiles, already installed in the field, behaves more stiff than predicted by the current design recommendations. The present study addresses the pile/seabed interaction problem, related to the stiffness of the monopile by means of a numerical model and experimental investigations. The numerical model is a 3D model. COMSOL Multiphysics, a finiteelement software, is used to calculate the soil response. The model is based on the Biot consolidation theory which involves a set of four equations, the first three equations describing the equilibrium conditions for a stress field, and the fourth one, the so-called storage equation, describing the conservation of mass of pore water with the seepage velocity given by Darcy’s law (Sumer and Fredsøe, 2002, chap. 10). The constitutive equation for the soil considered in the model is the familiar stress-strain relationship for linear poro-elastic soils. The so-called no-slip boundary condition is adopted on the surface of the rocking pile. The numerical model is validated against the laboratory experiments. The experimental setup includes a container (a circular tank with a diameter of 2 m and a height of 2.5 m), and a stainless steel model pile (with a diameter of 20 cm). Coarse sand (d50 = 0.64 mm) is used in the experiments. Pore-water pressures, pile displacements and forces on the pile are measured in the experiments. The pore-water pressure is measured at 12 points over a mesh extending 0.75 m in the vertical and 0.10 m in the radial direction (the measurement points closest to the pile being at 2 cm from the edge of the pile), using Honeywell pressure transducers. The pile displacement is measured, using a conventional potentiometer, while the force is measured with a tension/compression S-Beam load cell. The model, validated and tested, is used to calculate the soil response for a set of conditions, normally encountered in the field. The results are presented in terms of non-dimensional p-y curves, obtained from the numerical simulations. A parametric study is undertaken to observe the influence of various parameters on the latter. The parametric study shows that, for a given displacement, y, the soil