软岩隧道台阶法与全断面（含仰拱）法施工比较研究——以成兰铁路平安隧道为例

以成兰铁路平安隧道软岩段施工为背景，采用数值模拟、理论计算和现场试验等方法对全断面（含仰拱）法和台阶法施工时的围岩变形、初期支护受力及施工组织等方面进行比较分析，结果表明： 上下台阶法相比全断面（含仰拱）法开挖围岩要稳定，但全断面（含仰拱）法开挖累计变形量更小； 2种方法开挖产生的剪切、拉伸破坏区的范围大小相近，均能满足结构安全的需要，而全断面（含仰拱）法的施工质量比上下台阶法易于控制； 全断面（含仰拱）法在人员投入和施工进度等方面明显优于上下台阶法。

Comparison between Bench Method and Full face Method for  Ping’an Soft Rock Tunnel on Chengdu Lanzhou Railway

Comparison between bench method and full face method (including invert arch) for soft rock section of Ping’an Tunnel on Chengdu Lanzhou Railway is made in terms of surrounding rock deformation, primary support stress and construction organization by using numerical simulation, theoretical calculation and site test. The study results show that: 1) The stability of surrounding rock of tunnel constructed by bench method is superior to that constructed by full face method; and the accumulated deformation of tunnel constructed by full face method is smaller than that constructed by bench method. 2) The sizes of shear zone and tensile failure zone of tunnel constructed by 2 methods are almost the same. The construction quality of tunnel constructed by full face method is easier to control. 3) The full face method is superior to bench method in terms of labor and construction schedule.