海上风机复合式单桩基础载荷传递机理研究

Investigation of Load Transfer Mechanism of Hybrid Monopile Foundation for Offshore Wind Turbines

随着海上风电产业的快速发展,对于近海及潮间带海上风能的开发与利用逐渐趋于饱和.海上风力发电机的建造逐渐呈现由近海到远海,由浅水到深水的发展趋势,由此将带来更加严峻的海洋环境荷载.传统使用的单桩基础一般仅适用于浅海区域,其直径随着建造水深的增加迅速增加,由此带来高昂的建造以及施工成本使其无法适用于深海环境.借鉴带有稳定平台的可嵌入式挡土墙的设计理念,提出一种可用于海上风力发电机的新型复合式单桩基础,其一般由单桩和重力盘组成.复合式单桩基础在单桩和重力盘协同承载作用下,承载性能大大提升,具有更为广阔的发展前景.为了充分掌握这种新型基础形式的承载特性,首先开展了一系列离心机试验,研究其在砂土中的水平承载响应.基于离心机试验的高质量验证,利用ABAQUS有限元分析软件建立数值模型,研究单桩与重力盘之间的连接方式对整体水平承载响应的影响.基于复合式单桩基础与土体之间的相互作用机理,深入研究了单桩与重力盘在不同连接方式下的破坏机理.研究表明,单桩与重力盘摩擦连接时,两者之间的摩擦系数对整体承载性能的影响可以忽略.单桩与重力盘光滑连接时会产生“阻替”现象,即两者之间缺失的摩阻力被支持力所代替.但是,由于光滑连接与摩擦连接时单桩与重力盘之间传力模式不同,桩-盘-土相互作用有所差别,造成整体水平承载性能的改变.

With the development of the offshore wind industry,the use of offshore wind power in coastal areas becomes saturated.The construction water depth and the distance from the shoreline of an offshore wind turbine present increasing trends,resulting in severe environmental conditions.The pile diameter remarkably increases,causing high costs of construction and installation.The traditional monopile foundation is gradually discarded because of the cost problem.An innovative hybrid monopile foundation is proposed based on the embedded retaining wall with a stable platform.The hybrid monopile foundation comprises a monopile and gravity wheel,having the advantages of larger bearing capacity due to the collaborative capacity of the monopile and gravity wheel.To study the horizontal bearing characteristics of the hybrid monopile foundation,a series of centrifuge tests were conducted to investigate the lateral bearing response in the sand.Moreover,a finite element model was established using ABAQUS,validated by the centrifuge tests.Further studies regarding the effect of the pile-wheel connection mode on the overall bearing response were performed.The failure mechanism was investigated in terms of the pile-wheel-soil interaction.The results show that the friction coefficient has a negligible effect on the lateral bearing capacity of the hybrid monopile foundation with the friction connection.The“replaced-friction”phenomenon occurs at the hybrid monopile foundation with a smooth connection,effectively limiting the relative movement between the monopile and gravity wheel.The load transfer mechanism is various between the smooth and friction pile-wheel connection modes,which significantly impacts the pile-wheel-soil interaction as well as the lateral bearing characteristics.