基坑开挖对既有近距离下卧隧道影响实测分析

Measurement and Analysis of the Influence of Foundation Pit Excavation on Existing Short Distance Tunnel

为研究基坑开挖施工对既有近距离下卧隧道变形的影响,结合南宁某基坑工程,论述并验证既有隧道的加固保护措施,并通过基坑施工过程中对下卧隧道的全过程监测,分析基坑开挖施工对下卧隧道的影响。结果表明:开挖阶段管片发生明显的突变上浮,靠近基坑中部区域的隧道管片变形较大;左右线上浮变形初期受开挖顺序影响很大,最终表现为卸荷量大的一侧变形较大,同时左右线隧道的变形在逐渐趋于一致;分区开挖对管片的净空收敛没有明显的抑制作用;隧道上覆土过浅时,结构浇筑会对管片产生明显的加载压缩效应。

To study the influence of foundation pit excavation on the deformation of the tunnel located below the foundation pit and have a short distance to it,the reinforcement and protection measures of the existing tunnel were studied and verified,by the foundation pit project in Nanning.Through the foundation pit construction's whole process in-situ monitoring on underlying tunnel,the impact of foundation pit excavation on the underlying tunnel was analyzed.The result shows that there is an obvious mutation in the segment during excavation,and the tunnel segment close to the central area of the foundation pit has a large deformation.The initial floating deformation on the left and right tunnel is greatly affected by the excavation order.Finally,it manifests that the deformation of the side with a large discharge volume is deformed more.While the deformation of the left and right tunnel tends to be consistent.The partition excavation has a little effect on net-empty convergence of segment.In addition,the structural pouring would have a significant loading compression effect on the pipe,when the soil on the tunnel is too shallow.