天生桥隧道古溶蚀洼地段初支大变形控制技术

Technology for Large Deformation Control of Primary Support of Tianshengqiao Tunnel in the Ancient Karst Depression Section

沪昆客运专线天生桥隧道通过古溶蚀洼地段，围岩具有中等～强膨胀性，遇水后发生软化，导致上台阶初期支护产生49 m长、最大4．2 m的沉降量。通过采用在未变形段加强初期支护强度、增加临时支撑，以及在大变形产生段施工中采用上台阶回填、超前帷幕注浆、初期支护及二次衬砌加强、拱墙径向注浆、拱脚部位锁脚锚管加强、上台阶设置＋32纵向槽钢梁、基底钢管桩注浆加固等综合技术，成功控制围岩变形，顺利通过大变形段，对同类地质条件工程具有重要参考价值。

The surrounding rock of ancient karst depression section where Tianshenqiao tunnel passes through onShanghai-Kunming Passenger Dedicated Line is of medium to strong expansibility and is softened when the waterinfiltrates into the rock, which leads to settlement with a length of 49 m and a depth of 4.2 m in the primary support ofupper bench. In the section without deformation, the primary support has been strengthened and temporary support hasbeen increased. In the large deformation section, such comprehensive construction technologies have been used as upperbench backfill, advanced curtain grouting, strengthening of primary support and secondary lining, radial grouting in thearch wall, strengthening of locking anchor pipes at the arch foot, setting of qb32 mm longitudinal steel channel beams atthe upper bench and grouting strengthening of pipe pile at the bottom of the tunnel. The above measures have effectivelycontrolled the deformation of surrounding rock and ensured the construction of the tunnel is successful in the largedeformation section, which can provide important reference for projects under the similar geological conditions.