盾构开挖对桩基内力和变形的影响

Influence of shield excavation on internal forces and deformation of pile foundation

为研究盾构开挖对建筑物的影响,以某6层框架结构为研究对象,考虑上部结构-桩基-土体的共同作用。采用有限元软件ABAQUS6.14-1建立了盾构隧道、土体、桩基、上部框架的整体三维有限元模型,计算分析盾构下穿框架结构对桩基础变形和内力的影响。有限元计算结果表明:桩距盾构轴线的距离不同对桩底水平位移的影响比桩顶大,不同位置的桩的轴力受盾构开挖的影响各有不同,当开挖面推进到桩轴线并前进4倍洞径以内时桩的水平位移、弯矩和轴力的变化最为显著,桩上部所受弯矩较大且距地面0.2倍桩长处弯矩最大,应用采桩基础托换的方法减小该位置处的桩身弯矩。

In order to study the influence of shield excavation on buildings, a 6-layer frame structure is taken as the research object, and the interaction of superstructure-pile foundation-soil is considered. The finite element software ABAQUS6.14-1 is used to establish the overall three-dimensional finite element model of shield tunnel, soil, pile foundation and upper frame. The influence of shield structure on the deformation and internal force of pile foundation is calculated and analyzed. The results of finite element analysis show that the influence of shield excavation on the axial force of piles at different positions is different due to the different distance between the piles and the shield axis. The horizontal displacement, bending moment and axial force of the pile are most notable when the pile axis moves forward within 4 times of the hole diameter. The bending moment at the upper part of the pile is larger and the bending moment at the pile length of 0.2 times the ground is the largest. Appropriate methods should be taken to reinforce this position to enhance flexural rigidity.