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大西客专上白隧道出口工区隧道拱部为干燥粉细砂地层,下部为黄土地层。粉细砂层含水量小、粒径均匀,自稳性能极差,若采用普通注浆方式固结砂层其效果差,施工过程中经常出现流沙涌砂情况,无法保证隧道施工安全。经过对多种预支护技术的对比分析,决定采用水平旋喷预支护后再采用三台阶法开挖,并用三维数值方法分析隧道施工过程的力学特性,现场监测结果和施工效果表明,所采用施工方案能有效保证隧道施工安全。
Big West Passes tunnel exit tunnel area arch Department of dry powder sand formation, the lower part of the loess formation. The fine sand layer has small water content, uniform particle size and extremely poor self-stability. If ordinary grouting method is used to consolidate the sand layer, its effect is poor. During the construction process, the situation of sand pouring sand often occurs and the construction safety of the tunnel can not be guaranteed. After comparative analysis of a variety of pre-supporting technology, it is decided to adopt horizontal jet-jet pre-support and then use three-step method to excavation. The three-dimensional numerical method is used to analyze the mechanical characteristics of tunnel construction. The on-site monitoring results and construction results show that the construction Program can effectively ensure the safety of tunnel construction.