上硬下软地层铁路大断面隧道施工方法优选

内蒙古八苏木铁路隧道穿越上硬下软地层,本文利用有限差分软件对该隧道的施工方法进行优选。结果表明:交叉中隔壁法和三台阶临时仰拱法对隧道初期支护结构位移的控制效果较好,台阶法的控制效果最差;三台阶临时仰拱法内力分布最均匀,对隧道初期支护结构整体的轴力、弯矩控制效果最好,三台阶七步开挖法的控制效果最差;不同施工方法下隧道初期支护结构的最小安全系数均大于规范值,其中三台阶临时仰拱法的最小安全系数最大。综合比较,三台阶临时仰拱法优于其他3种施工方法。经在工程中应用,该施工方法效果良好。

Optimization of Construction Method for Railway Tunnel with Large Section in Upper-hard and Lower-soft Strata

The Basumu railway tunnel in Inner Mongolia passes through the upper-hard and lower-soft strata.In this paper,the f inite difference software was used to optimize the construction method of the tunnel.The results show that the center cross diagram method and three-step temporary inverted arch method have better control effects on the displacement of the tunnel initial support structure,while the step method has the worst control effect.The three-step temporary inverted arch method has the most uniform internal force distribution and the best control effect on the overall axial force and bending moment of the tunnel initial support structure,while the three-step seven-step excavation method has the worst control effect.The minimum safety factors of tunnel initial support structure with different construction methods are all larger than the standard value,and the minimum safety factor of three-step temporary inverted arch method is the largest.By comprehensive comparison,the three-step temporary inverted arch method is superior to the other three construction methods,which has good effect by utilized in engineering application.