增层开挖条件下既有建筑群桩基础三维数值分析

Three-dimensional Numerical Analysis of Group Pile Foundation for Excavation Beneath Existing Buildings

既有建筑下增层开挖对群桩基础的影响不同于基坑开挖对待建建筑桩基的影响,采用HARDENING-SOIL弹塑性模型模拟土体及接触面单元模拟桩土相互作用,分别就摩擦型桩和端承型桩,建立桩筏基础-地基-增层开挖三维有限元模型,分析增层开挖后桩顶反力、桩身轴力、桩侧摩阻力、桩体水平位移和桩身弯矩分布规律,并对比分析桩顶Q-S曲线和桩侧摩阻力在开挖前后变化规律,通过研究,取得了增层开挖对既有建筑群桩基础影响的基本认识,揭示了开挖后摩擦型桩和端承型桩不同变化规律,这些规律有助于类似工程的设计施工。

The effects of excavation beneath the existing building on group pile foundation is different from excavation in building field on pre-installed pile.In this paper,the HARDENING-SOIL model and contact surface model were adopted to simulate the characters of soil and the interaction between pile and soil respectively,a three-dimensional finite element model based on the interaction of piled raft foundation,ground and excavation was established for friction pile foundation and end-bearing pile foundation separately.By this way,the distribution of pile-head force,pile axial force,pile shaft resistance,pile displacement and pile bending moment after excavation was analysed.What’s more,comparison of Q-S curves as well as pile shaft resistance before and after excavation was discussed.Through this study,the basic knowledge of the effects of excavation beneath the existing building on group pile foundation were initially obtained,the different variation of friction pile and end-bearing pile after excavation were revealed,which would be useful for the design and construction of similar projects.