基坑上跨已运营地铁隧道的设计及实测分析

Design and field measurement of excavation on operating metro tunnels

基于某箱型隧道上跨已运营地铁隧道基坑工程,对该工程支护结构及基坑开挖方式进行设计。有限元分析及实测结果表明,采用人工抽条放坡开挖+板锚支护可以有效地控制基底土体的回弹和既有地铁隧道的变形。该工法充分利用基坑开挖的时空效应,人工抽条放坡开挖主要用于控制在基坑开挖过程中引起的土体的回弹及地铁隧道的上浮;而板锚支护的设置,则可有效地约束基坑开挖后由于土体卸载引起的地铁隧道变形。该工程采用数值分析进行施工前预测与自动化监测指导施工相结合方法也是工程成功实施的关键,其成功经验可为类似的工程提供一定的参考。

Based on the foundation pit of a box tunnel crossing over operating metro tunnels, the form of supporting structure and the excavating mode are designed. The finite element analysis and measured results show that the method to use artificial strip-slope excavation and board-anchor supporting structures to restrict the rebound of bottom soils and the deformation of the operating metro tunnels are very effective. The method considers the time-space effect of excavation. The artificial strip-slope excavation is mainly used to control the rebound of bottom soils and to restrict the floating of tunnels during excavation. The board-anchor supporting structure is used to restrict the deformation of the tunnels due to the soil unloading after excavation. This project adopts the finite element numerical analysis method to forecast the deformation before construction and the automatic monitoring method to instruct construction. The successful experience of this project may provide valuable reference for the similar projects.