复合地层中基坑开挖对下卧隧道变形影响研究

Study on Influence of Excavation of Foundation Pit on Deformation of Underlying Tunnel in Complex Ground

在城市建设中,基坑开挖会引起附近地层变形,造成附近地下隧道变形,从而对地铁隧道正常运行造成安全隐患。以南京地铁3号线明发广场站至南京南站区间地下空间开发为背景,采用数值方法对复合地层中基坑开挖对周边土体及隧道变形影响进行研究,重点分析基坑开挖宽度与隧道直径比(L/D)和复合地层模量比(E2/E1)变化对土体及隧道变形的影响。主要研究结果如下:1)当L/D<3时,基坑底部回弹和隧道变形随基坑宽度增加而增大,当L/D≥3时,基坑底部回弹和隧道变形不受基坑宽度增加的影响;2)当E2/E1<8时,基坑回弹和隧道变形随模量比的增加而迅速降低,当E2/E1≥8时,基坑底部回弹量和隧道变形不受模量比的影响。

During foundation pit excavation, deformation often occurs to the tunnel lying underneath, as a result, the normal operation and safety of the Metro tunnel lying underneath cannot be guaranteed. In this paper, the influence of the excavation of foundation pit on the deformation of the underlying tunnel and the surrounding soil mass in complex ground is studied, and the influence of the variation of the ratio between the excavation width of the foundation pit and the diameter of the tunnel （L/D） and the influence of the variation of the ratio of the modulus of the complex ground （E2/E1 ） on the deformation of the soil mass and the tunnel are analyzed in detail, with the development of the underground space along the running tunnel from Mingfa Square Station to Nanjing South Railway Station on Line 3 of Nanjing Metro as an example. Conclusions drawn are as follows： 1 ） When L/D〈 3, the rebound of the floor of the foundation pit and the deformation of the underlying tunnel increase as the excavation width of the foundation pit increases; when L/D〉~3, the rebound of the floor of the foundation pit and the deformation of the underlying tunnel are not influenced by the excavation width of foundation pit ; 2） When E2/E1 〈 8, the rebound of the floor of the foundation pit and the deformation of the underlying tunnel reduce dramatically as the ratio of the modulus of the complex ground increases; when E2/E1 〉18, the rebound of the floor of the foundation pit and the deformation of the underlying tunnel are not influenced by the ratio of the modulus of the complex ground.