Design parameters and influencing analysis of post-expansion excavation method without pilot tunnel in continuous arch tunnel
In order to study the design parameters and their influence on the stability of double-arch tunnel during the con-struction by the post-expansion excavation method without pilot tunnel,the numerical simulation method was used to analyze the influence of four parameters on the stress and deformation of the continuous arch tunnel,including the staggered distance of main tunnel,the length of steps,the thickness of middle partition wall,and the application time of second lining,and the re-sults were compared with the on-site monitoring results.The results show that when the staggered distance of main tunnel rea-ches 75 m,it can not only ensure the deformation stability of the first tunnel,but also shorten the construction period.The length of steps of the first tunnel can be taken according to the value of single tunnel,and the length of steps of the rear tunnel is recommended to be controlled as 5～10 m.Considering the influence of construction disturbance,the thickness of middle partition wall in the tunnel is more reasonable in the range of 1.4～1.6 m.The second lining of the first tunnel should be more than 35 m distance in front of the tunnel face of rear tunnel,which is conducive to the control of tunnel stability.The re-search results can provide a reference for the construction of tunnel projects.
double-arch tunnelconstruction method without pilot tunneldesign parameter
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