公铁合建双层盾构隧道设计关键技术

Key Design Technologies for Integrated Highway-Metro Double-Layer Shield Tunnels

为解决公铁合建双层盾构隧道面临的总体布置、结构设计、汽车与地铁车辆联合振动以及通风排烟等技术难题,以武汉长江公铁隧道和济南黄河济泺路隧道工程实践为基础,采用方案综合比选、2.5维数值计算等方法,对公铁合建双层盾构隧道设计关键技术进行系统研究。结果表明:1)通过对隧道平面、纵断面和横断面的合理优化布置,并在废水泵房段、疏散楼梯段采取特殊布置方案,可减少公铁合建盾构隧道地下空间占用,并提高断面利用率,减小盾构隧道外径;2)采用半预制半现浇的管片+非封闭内衬结构型式,能充分发挥内部结构与管片衬砌的联合承载作用,显著减小河床冲淤作用;3)汽车与地铁联合振动作用对隧道影响较小,隧道基底饱和粉细砂地层不会发生液化;4)地铁隧道采用分段纵向烟道,可解决地铁长大区间无风井条件下的排烟难题,同时提高疏散便捷性,并大幅降低建设难度;5)公铁合建隧道在运营管理上不可避免地会出现交叉和影响,建议在管理界面划分和投资分劈上提前研究,便于决策。

The integration of highway and metro systems within a double-layer shield tunnel presents several challenges,including layout design,structural integrity,combined vibrations from vehicles and trains,and ventilation and smoke extraction.A case study is conducted on the Jiluo road Yangtze river-crossing tunnel in Wuhan,China,and key design technologies for double-layer shield tunnels are analyzed through comprehensive comparison and 2.5-dimensional numerical simulations.The findings include:(1)The underground space required for the highway-metro double-layer shield tunnel can be minimized by optimizing the layout of the tunnel's plane,longitudinal and horizontal cross-sections,and implementing specialized designs for wastewater pump rooms and evacuation staircases.This approach enhances the cross-sectional utilization and allows for a reduction in the tunnel's outer diameter.(2)The use of a semi-prefabricated and semi-cast segment combined with a nonclosed lining structure improves the overall bearing capacity of the internal structure and segment lining,significantly reducing riverbed erosion and deposition.(3)The combined vibrations from automobiles and metro trains slightly affects the tunnel,and the saturated fine sand stratum at the tunnel base remains stable without liquefaction.(4)Segmented longitudinal flues in the metro tunnel effectively manage smoke extraction over long sections without requiring air shafts,facilitating evacuation and greatly reducing construction challenges.(5)The inevitable cross-influence between highway and metro operations necessitates advance study of management interfaces and investment division to aid in effective decision-making.