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新建贵广铁路四寨2号隧道下穿已运营厦蓉高速公路瑞坡隧道,且立交段穿越富水断层破碎带,施工难度大,风险高。为分析交错新建隧道对既有公路隧道的影响,建立三维数值仿真模型对交错隧道的施工力学行为进行了研究。结果表明,新建隧道下穿施工对既有隧道安全存在一定的影响,引起既有隧道纵向发生明显的不均匀沉降;受断层破碎带影响,新建隧道开挖前后,既有隧道衬砌结构安全系数大幅度降低;新建隧道穿过断层破碎带段,采取大管棚辅以45°大外插角注浆小导管进行超前预加固后,选择CRD工法下穿既有隧道,可将既有隧道沉降控制在20mm的允许变形控制基准值内;基于计算结果和施工风险分析,总结提出了交错隧道施工风险规避技术措施。
The newly built Siu Zhai No.2 tunnel under the Gui-Guang Railway underlies the Ruopo Tunnel under operation of the Xialong Expressway and the overpass passes through the Fusui fault zone, making construction more difficult and riskier. In order to analyze the influence of staggered new tunnel on the existing highway tunnel, a three-dimensional numerical simulation model was established to study the construction mechanics behavior of the staggered tunnel. The results show that the construction of the new tunnel underpass has some influence on the safety of the existing tunnel, causing obvious uneven settlement of the existing tunnel in the longitudinal direction. Affected by the fault zone, the safety factor of the existing tunnel lining is large before and after excavation After the new tunnel passes through the fault broken belt section and takes the large pipe shed and the 45 ° extra-large grouting small duct for advanced pre-reinforcement, the CRD tunneling method can be used to wear the existing tunnel and the existing tunnel settlement control Based on the calculation results and construction risk analysis, the technical measures of risk avoidance in staggered tunnel construction are put forward.