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| Numerical Calculation and Analysis on Effects of Pilot Heading of Xinchengzi Tunnel with Small Spacing |
| LIU Zhi-qiang, SONG Ye, WANG Ren-jie, WU Jian |
| (China Railway Southwest Research Institute Co. Ltd, Chengdu, Sichuan 611731, China) |
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Abstract Abstract：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 heading 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 heading is released, the mean and maximum values of deformations in left and right tubes are reduced by 7%～20%.（5）The research results can provide reference for the design and construction of the similar tunnel in squeezing rocks.
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Received: 01 August 2017
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2018, Vol. 35 
