吸力式筒形基础沉贯过程的大变形有限元模拟

吸力式筒形基础在海洋工程中已获得越来越广泛地应用，其安装过程的数值模拟对指导工程实践具有重要意义。在大型通用有限元软件ABAQUS平台上建立了二维轴对称模型，基于ALE（任意拉格朗日-欧拉法）技术模拟了黏土中吸力筒的大变形沉贯过程。模拟过程利用了子程序VUFIELD控制土体的不排水抗剪强度和弹性模量随土体深度变化。参照离心机试验及理论计算，对模型进行验证。利用已验证模型分析不同吸力下沉贯阻力、土塞高度，并讨论了筒壁摩擦特性。数值计算结果表明，ALE技术能有效地模拟吸力筒贯入过程，避免网格畸变。贯入方式对贯入阻力影响很大，吸力式贯入阻力明显低于压力式贯入阻力。进一步研究发现，随着最终吸力值的增大，沉贯阻力会显著降低，土塞高度会显著提高。对内壁摩擦特性的研究表明，内壁摩擦阻力是导致沉贯阻力改变的主要因素，并且相比吸力式贯入方式，筒壁摩擦特性会对压力式贯入造成更大的影响。

Large deformation finite element simulation of suction bucket foundation during penetration

Suction bucket foundations are increasingly used in ocean engineering. The numerical analysis of the installation procedure is helpful in engineering practice. A two-dimensional axisymmetric model has been implemented into the finite element software ABAQUS based on the ALE (Arbitrary Lagrangian-Eulerian formulation) technique, which will be used to simulate the penetration process of the suction bucket foundation in clay. The undrained shear strength and elastic moduli of soil vary with the soil depth, which are considered through the subroutine VUFIELD. Centrifuge testing results and theoretical calculations are used to validate the proposed FEM model, and some key parameters including the penetration resistance, the height of soil plug under different suctions and the bucket wall friction are examined. The numerical results show that the ALE technique is capable of simulating the suction bucket penetration without mesh distortion problems. The installation method can significantly affect the penetration resistance, namely, the suction penetration can reduces the resistance significantly compared to the purely jacked penetration. In addition, it is found that as the final suction increases, the penetration resistance reduces and the soil plug height increases. It is also shown that the internal friction has a significant contribution to the penetration resistance and the properties of soil-bucket wall friction exert more significant impact on the purely jacketed penetration than on the suction penetration.