地铁盾构近距离侧穿桥梁桩基变形影响研究

Effects of Pile Foundation Deformation of Metro Shield Short-distance Side-through Bridge

以地铁盾构隧道侧穿城市立交桥工程为背景,介绍桥梁桩基保护措施并对下穿施工对桩基的影响性进行分析。采用MIDAS/GTS NX软件建立三维有限元模拟,通过施工阶段分析,结合实测数据,分析下穿工程对桩基变形影响,结果表明,通过偏离系数对实测数据分析,在穿越鼓楼立交风险源,区间随下穿过程中的结构控制值偏离系数最大为2.7 mm,偏离系数等级为一级,表明结构安全性能未受到盾构掘进干扰,结构安全性能损伤轻微,表明该方案在控制下穿工程中桩基变形有较好的效果;盾构隧道穿越桥梁桩基采用袖阀管对桩基底部进行跟踪注浆时,通过控制底部跟踪注浆范围,最大位移由5.5 mm减少至4.7 mm,即横向加固区域取桩基直径的1.5倍,竖向区域取桩长1/6时,对桩基加固效果最为理想。

With the metro shield tunnel passing through the urban overpass as the background,the protection measures of the bridge pile foundation are introduced and the influence of the underpass construction on the pile foundation is analyzed.The three-dimensional finite element simulation is established by using MIDAS/GTS NX software.Through the analysis of the construction stage and combined with the measured data,the influence of the undercut project on the deformation of pile foundation is analyzed.The results show that through the analysis of the deviation coefficient to the measured data,in the process of crossing the risk source of Gulou Interchange,the maximum deviation coefficient of structural control value is 2.7 mm,and the grade of deviation coefficient is first class,indicating that the structural safety performance is not disturbed by shield tunneling.The damage to the safety performance of the structure is slight,which shows that the scheme has a good effect on the deformation of pile foundation in controlled piercing engineering.When the shield tunnel traverses the pile foundation of the bridge,the sleeve valve pipe is used to track the bottom of the pile foundation,and by controlling the bottom tracking grouting range,the maximum displacement is reduced from 5.5mm to 4.7mm;that is,when the transverse reinforcement area is 1.5 times of the pile foundation diameter,and the pile length is 1/6 in the vertical area,the pile foundation reinforcement effect is the best.