地铁隧道下穿施工对既有运营隧道的影响分析

An Analysis of the Influence of the Construction of a Subway-Undercrossed Tunnel on an Existing Tunnel in Operation

针对隧道工程中新建隧道近距离下穿既有运营隧道工况,以重庆轨道交通4号线与既有3号线隧道交叉区段为工程背景,考虑开挖方法、支护情况、两洞掌子面间距和每次开挖进尺等参数,采用数值模拟方法分析了新建地铁隧道下穿既有运营隧道施工对既有隧道的影响,并与现场实测数据对比分析,得出了一些结论:新建隧道的施工对既有结构的内力及变形影响都非常明显;双洞同时施工时,应尽量增加两洞内掌子面的间距,在既有结构较近范围内,两个隧洞应避免同时施工;新建隧道开挖后应及时支护并加大初衬中钢拱架的布置密度;在通过既有隧道下方时,每次开挖进尺的减小也能降低对既有隧道结构的影响。

With the construction conditions of the newly-built tunnel projects some of which undercross the existing tunnels in operation taken into consideration,with the tunnel-crossing section of Line 4 of the rail transit in Chongqing that under-crosses existing Line 3 as the engineering background, and also with the excavation method,the supporting circumstances,and other parameters such as the spacing distance between the work faces of the two tunnels and the cutting footage of each excavation operation taken into consideration, the numerical simulation method is adopted to analyze the effect of the construction of a newly-built metro tunnel under-crossing an existing tunnel in operation on the existing tunnel in operation.The simulated results are compared with those of the real survey at the site,and analyzed,upon the basis of which obtained are the following conclusions: the effect of the construction of the tunnel being newly built on the internal forces and deformation of the existing structures is very obvious;when two tunnels are built at the same time, the spacing distance between the two work faces in the two tunnels should be kept as great as possible;if the existing structure is located within a nearby range, the construction of the two tunnels should avoid being started at the same time;after the excavation of the tunnel to be newly-built is started, it should be timely supported, with the laying density of the steel arch brackets for the initial lining increased;when the excavation is performed right under the existing tunnel, the decrease in the cutting footage of each-time excavation may also reduce the effect of the construction on the structure of the existing tunnel.