邻近基坑卸荷情况下地铁隧道变形规律及加固措施

Deformation Laws and Reinforcement Measures of Subway Tunnel Under Unloading of Neighbor Foundation Fit

以西安一地铁区段附近地铁车站基坑开挖为工程背景,建立三维有限元模型,对基坑卸荷开挖进行动态模拟,分析开挖过程中既有隧道结构的变形规律,探究保证隧道结构稳定的加固措施。结果表明:基坑卸荷完成后,近基坑隧道结构变形较大,且竖向变形远大于水平变形,施工过程中应重点监测管片竖向变形;基坑底板的竖向位移变化速率和位移均较大,须加强监测并采用控制措施限制坑底土体的回弹变形;采用环向管幕和抗浮锚索综合加固措施,在基坑全部卸荷完成后,隧道隆起最大值为9.68 mm,水平位移最大值为1.92 mm,满足隧道变形控制标准,变形控制效果显著。

Taking the foundation pit excavation of a subway station near a subway section in Xi’an as the engineering background,a three-dimensional finite element model was established to dynamically simulate the foundation pit excavation and unloading,analyze the deformation laws of the existing tunnel structure in the excavation process,and explore the control and reinforcement measures to ensure the stability of the tunnel structure.The results show that after the unloading of the foundation pit,the deformation of the tunnel structure near the foundation pit is large,and the vertical deformation is much larger than the horizontal deformation.The vertical deformation of the segment should be monitored during the construction process.The change rate of the vertical displacement and displacement of the foundation pit bottom plate are large,so it is necessary to strengthen the monitoring and adopt control measures to limit the rebound deformation of the soil at the bottom of the pit.The comprehensive reinforcement control measures of circumferential pipe curtain and anti-floating anchor cable are adopted.After the foundation pit is fully unloaded,the maximum uplift of the tunnel is 9.68 mm and the maximum horizontal displacement is 1.92 mm,which meets the tunnel deformation control standard,and the deformation control effect is remarkable.