暗挖隧道近距下穿既有区间隧道施工方案对比研究

A Comparative Study of the Construction Schemes for Undercut Tunnels Undercrossing Existing Sectional Tunnels at a Short Distance

以北京地铁17号线东大桥站下穿既有6号线区间线为背景,研究了新建双洞隧道下穿既有隧道时不同施工方案对既有隧道和新建隧道的影响。采用有限元软件MIDAS-GTS建立隧道施工模型,研究平顶直墙+管棚超前支护、拱顶直墙两种方案施工时既有隧道和新建隧道的变形和受力特征。结果表明:平顶直墙+管棚支护相较于拱顶直墙方案既有隧道沉降减小15%,最大压应力减小32%,最大拉应力减小53%,且在施工过程中既有隧道的位移和应力更小,平顶直墙+管棚支护是更适合的施工方案。

With the Dongdaqiao Station of Line 17 of Beijing Subway undercrossing the existing sectional line of Line 6 as the background,studied in the present paper are the effects of different construction schemes on the existing tunnel and the newly-built tunnel when the new double-hole tunnel undercrosses the existing tunnel.The finite element software MIDAS-GTS is used to establish the tunnel construction model,and the deformation and stress characteristics of the existing and the newly built tunnels are studied in the two construction schemes:one is with the flat-topped straight wall+tube canopy advanced support,and the other is with the straight wall with the arch roof.The results show that,compared with those of the newly-built tunnel with the straight wall with arch roof,the settlement,the maximum compressive stress and the maximum tensile stress of the existing tunnel are reduced respectively by 15%,32%,and 53%.Besides,the displacement and stress of the existing tunnel tend to be even less in the process of construction,from which it can be concluded that the flat-topped straight wall+tube shed support is a more suitable construction scheme.