超浅埋暗挖双层隧道下穿城市主干道设计

城市内双层隧道下穿既有主干道,因受线型、埋深等影响,存在“浅埋、地质条件差、周边环境复杂”等特点,工程实施难度大。结合工程案例,全面介绍了超浅埋、小间距双层隧道采用“大管棚+小导管+掌子面TSS注浆”的超前加固措施、双层衬砌结构配合CRD或双侧壁导坑法的支护方案,以及近接桥梁“加桩补强法”的保护方案是合理可行的;并提出地表沉降控制值可结合工程情况突破常规值(+10 mm~-30 mm),加强分块施工的初支拱脚刚度和拱部回填注浆有利于控制地表沉降的建议。

Design of Double Deck Tunnel under Passing Urban Main Road with Super Shallow Buried Subsurface Excavation Method

Because of the influence of alignment and buried depth, the double deck tunnels in the city have the characteristics of shallow buried, poor geological conditions and complicated surrounding environment, so it is difficult to carry out the projects. Based on the successful construction of the project, the design contents are introduced about the double deck tunnel that is super shallow buried and small spacing, which include the auxiliary construction measures of "canopy tube + small pipe + TSS grouting on excavation face",CRD or double side drift method which is adopted with the double-layer lining structure,and the protection scheme of the adjacent bridge. The control value of ground settlement can break through the conventional value (+10 mm~-30 mm), which is associated with the engineering situation. It is suggested that the stiffness of the arch foot and the backfill grouting at the arch are beneficial to the control of ground settlement.