海上风电机组筒型基础工作及承载特性研究

Study of working mechanism and bearing capacity behavior of bucket foundation for offshore wind turbine

筒型基础是一种新型的海上风电基础,由于其具有减少工程量、节省投资、缩短施工时间、可重复使用等优点,在某些领域正在逐步替代桩基和重力式基础。目前工程上对筒型基础的设计还没有现成的规范可供使用,一般是将筒内部土体与筒壁视为一体,然后采用简化的极限平衡方法进行设计计算,不能反映筒内土体的工作特性。以福建近海某风电基础工程为依托,采用大型有限元软件ABAQUS对海上风机单筒基础的承载特性进行了三维有限元数值分析。根据海上风机的受力特点,考虑基础隔舱的作用效果,建立了筒型基础的简化模型与有无隔舱的计算模型。计算结果表明:筒型基础在受荷过程中,基础内部土体产生屈服变形,使得筒型基础的承载特性不同于简化极限平衡方法。两者之间的差异使得实际的地基承载能力比极限平衡方法计算所得的要小。此外,对现行简化计算方法的误差进行了估计,并对筒型基础承载力计算提出建议,可供筒型基础设计者参考。

Compared with traditional offshore foundation structure,bucket foundations which are large cylindrical structures open at the base and close at the top may realize economical advantages over traditional driven piles due to the speed of installation,elimination of the pile driving process,and reduction in quantities and material costs.Though bucket foundation is a new foundation type for offshore wind turbine,there have no standards for bucket foundation designing up to now.In designing the bucket foundation,the simplified limit equilibrium method is usually adopted,in which the soil inside the bucket and the skirt of the bucket are assumed to form a whole foundation.But this method cannot reflect the working mechanism of the internal soil.Based on a foundation of offshore wind turbine in Fujian,adopting the finite element software ABAQUS,the three-dimensional numerical analysis is performed to simulate the working mechanism and evaluate the bearing capacity behavior of bucket foundation.According to the bearing capacity of offshore wind turbine,the simplified model and models with or without compartments are established with the considering of the compartments effect.According to calculation results,the bearing characteristic of the bucket foundation is different from the simplified limit equilibrium method that the internal soil of the foundation yields first in the loading process.The difference leads the simplified limit equilibrium method will over estimate the bearing capacity of bucket foundation.In addition,the error of the bearing capacity calculated by the simplified limit equilibrium method is estimated.The suggestion about the bearing capacity of bucket foundation has reference value to project designer.