软弱围岩铁路隧道三台阶带仰拱一次开挖工法台阶高度优化研究

为进一步提高软弱围岩条件下隧道开挖的安全性及稳定性,本文依靠玉磨铁路新平隧道工程,利用有限差分数值模拟软件flac3 D,对软弱围岩铁路隧道三台阶带仰拱一次开挖工法的台阶高度进行优化研究,主要对比了5种不同台阶高度开挖方案的初期支护位移及内力.结果表明:(1)采用工况4(上台阶高度4 m、中台阶高度3．2 m、下台阶高...

Optimization of Bench Height in One-step Excavation for Three Benches with Invert of Railway Tunnels in Soft Rocks

In order to further improve the safety and stability of tunnel excavation in soft rocks,this paper takes Xinping Tunnel of Yuxi-Mohan Railway as a case,employs the finite difference numerical simulation software flac 3D to optimize the bench height in one-step excavation for the three benches with the invert of railway tunnels in the soft rocks,and mainly compares the initial supporting displacement and internal force of five excavation schemes with different bench heights.The results show that:(1)The vault settlement,arch shoulder convergence,and sidewall convergence of Case 4(upper bench height of 4 m,middle bench height of 3.2 m,and lower bench height of 5 m)are the smallest,which are 22.3 mm,3.17 mm and 11.9 mm respectively.(2)The structural safety of Case 4 is the highest,and the minimum safety factor is the largest,which is 2.83.(3)Considering the structural displacement and internal force,it is recommended to adopt the bench height of Case 4 in the soft surrounding rock section of Xinping Tunnel.The research results may be used for reference by similar projects.