浅埋偏压大断面隧道施工优化及受力特征分析

大断面浅埋偏压隧道洞口段施工困难,风险高;且受洞口复杂地质条件和施工空间效应影响,隧道支护结构变形和受力特性复杂,施工控制难度高。针对在建的宝兰客专小墁坪隧道出口浅埋偏压段的施工稳定性问题,采用数值模拟试验分析方法,研究了三台阶+临时横撑施工中不同上、中、下台阶错开距离时隧道的施工动态特性,分析了不同错开距离时隧道支护结构的变形和受力特点;基于数值模拟试验确定了大断面偏压隧道洞口段的施工方案,跟踪隧道施工进行的变形监测验证了推荐的三台阶+临时横撑施工中上台阶与中台阶错开5 m,中台阶与下台阶错开10~15 m(即1倍洞径)距离的施工参数经济、合理、可行,保证了隧道施工的安全,也为同类隧道工程的建设提供有益的借鉴和指导。

Analysis of Construction Optimization and Mechanical Characteristic of Shallow Large Section Tunnel

In the portal section of large section shallow tunnel under unsymmetrical pressure,the construction is hard and high-risk.It is caused by complex geological condition and spatial effect that the characteristics of deformation and stress in tunnel lining structure are complex,and the construction control is difficult.Stability of shallow bias tunnel section of Xiao Man-ping tunnel was analyzed with numerical simulation.Dynamic characteristics of construction and characteristics of deformation and stress in tunnel lining structure with three-step and temporary support method under different step staggered distance were researched.Based on the results of numerical simulation test,the construction scheme of large section biased tunnel entrance was established,the upper step staggers 5 meters with middle step,and the middle step staggers 10 to 15 meters with bottom step (as much as the diameter of the tunnel).Monitoring results of tunnel attest that the construction scheme is economical,reasonable and feasible.The result of the study not only ensures the safety of tunnel construction,but also provides useful reference and guidance for the construction of similar tunnel projects.