新城子隧道小间距段导洞作用效果计算分析

Numerical Calculation and Analysis on Effects of Pilot Heading of Xinchengzi Tunnel with Small Spacing

研究目的:小间距隧道的工程难点主要是群洞效应以及中间岩柱的稳定性问题,国内目前研究主要集中在浅埋、城市环境以及一般围岩环境,针对挤压性围岩中的小间距问题研究甚少。基于此,本文以兰渝铁路新城子隧道为工程背景,通过数值计算及数据统计分析的方法,研究挤压性围岩中小间距隧道导洞的作用效果,以期为相关工程提供参考。研究结论:(1)挤压性围岩小间距隧道,邻洞的存在对主洞开挖的影响包括中间岩柱的塑性变形和邻洞的变形释放,两种变形效应叠加产生相互影响;(2)先行洞室开挖的影响范围为掌子面前方1.5B,掌子面后方2B;(3)先行导洞的作用,可以明显减小后行洞室扩挖时对先行洞室的影响,同时本线的位移减小至无导洞的10%～20%,影响范围降至1.5B之内;(4)新城子隧道变形统计分析显示,后行左线变形小于右线11.6%～20.4%,当采用导洞应力释放后,左、右线平均值及最大值减小7%～20%;(5)该研究成果可为类似挤压性围岩隧道的设计与施工提供参考。

Research purposes： This study is aiming at the engineering difficulties of the tunnels with small spacing, including the multi - cavity effects and the stability of interval rock pillars. At present, the domestic current study is mainly focused on conditions of shallow - buried, urban region and general surrounding rocks and on the contrary, little study on tunnels with small spacing in squeezing rocks is made. In this paper, by means of numerical calculation and data statistic analysis, the effects of pilot headings with small spacing in squeezing rocks is studied, which can provide a reference for similar projects. Research conclusions： （ 1 ） For the tunnels with small spacing in squeezing rocks, the impacts of neighboring tunnel on main tunnel excavation include the plastic deformation of interval rock pillar and the deformation release of neighboring tunnel, of which two deformations shall be overlapped and interacted. （2） The influential range of beading tunnel excavation is between 1.5B in front of working face and 2B behind working face. （ 3 ） The effects of pilot heading can obviously reduce the impacts of following tunnel excavation on heading tunnel, meanwhile the displacement of tunnel with pilot headings can reduce to 10 ~ 20% of tunnel with no pilot headings and its influential range drops to within the limit of 1.5B. （4） The deformation statistics and analysis of Xinchengzi tunnel indicate that the deformation of following left tube is 11.6% - 20.4% less than that of right tube and when the stress of pilot maximum values of deformations in left and right tubes are reduced by 7% -20%. （ reference for the design and construction of the similar tunnel in squeezing rocks.