海洋平台大直径钢管桩打桩过程有限元分析研究

Finite element analysis on large diameter steel pipe pile driving of offshore platform

近年来海上工程的规模越来越大,为了满足工程需要,桩基设计常常采用大直径,大长度的钢管桩。打桩过程是个相当复杂的过程,不仅涉及到几何非线性、材料非线性、边界非线性,而且是个动力过程。有限元法在处理打桩分析方面具有很强的优势,采用PLAXIS对不同条件下的打桩问题进行了动力模拟分析。分析显示在打桩过程中,桩端土体会产生较大的水平位移和竖向位移,桩端土体和靠近桩端的部分土塞内会产生较大的超孔隙水压力。在砂土中,停锤较短时间也会使孔压迅速消散,这也是打桩中间的停锤会造成后续打桩困难的主要原因。

In recent years, with the development of offshore engineering, large diameter and deep penetration steel pipe pile foundations are often used in practice. Pile driving is a rather complex process, which involves not only the geometric nonlinear, material nonlinear, boundary nonlinear, but also dynamic analysis. Finite element method has advantages in dealing with this problem. In this study, PLAXIS was adopted to simulate dynamic analysis of pile driving under different conditions. Analysis resuhs show that in the process of pile driving, large horizontal displacement and vertical displacement of the soils at the pile tip may occur, and great excess pore water pressure may appear in the soils at pile tip and soil plug near pile end. In sand, driving suspending with short time also makes pore pressure dissipate rapidly, which is the main reason causing driving difficulties after installation delay.