随着我国城市化进程的快速推进,地铁沿线的商业区正在迅速发展,此趋势使得越来越多基坑工程面临跨越地铁隧道的问题。本文依托某地铁运营段上方基坑开挖对隧道影响的工程案例,运用现场监测和数值模拟方法,针对基坑开挖对其正下方运营地铁隧道形变的问题展开深入研究。在验证数值模型可靠性后,利用三维有限元软件模拟分析桩径、桩间距、排桩数和多种新型工法复合防控措施,进一步优化基坑开挖与支护方案,以保障地铁隧道安全与稳定。确定了针对该工程打设抗拔桩最佳的桩长、桩径、桩间距和排桩数量,以此控制基坑开挖过程隧道的上浮量。另外,模拟分析了扩底桩和导向钻管两种新工法的控制效果,成果可为类似工程提供参考。

With the rapid progress of urbanization in China, the commercial areas along the subway are developing rapidly, and this trend makes more and more pit projects face the problem of crossing the subway tunnel. This paper relies on an engineering case of the impact of pit excavation on the tunnel above a subway operation section, and uses on-site monitoring and numerical simulation methods to carry out an in-depth study on the deformation of the subway tunnel directly underneath the operation of pit excavation. After verifying the reliability of the numerical model, three-dimensional finite element software is used to simulate and analyze the pile diameter, pile spacing, number of piles in rows, and a variety of new methods of composite preventive and control measures, to further optimize the pit excavation and support scheme to ensure the safety and stability of the subway tunnel. The optimum pile length, pile diameter, pile spacing and number of piles are determined for the project to control the uplift of the tunnel during foundation pit excavation. At the same time, the control effect of two new methods, namely, expanded bottom piles and guided drilled pipe, is simulated and analyzed in similar projects, which provides a reliable construction theoretical basis and construction scheme reference for similar pit excavation above existing tunnels.