浅埋砂质新黄土隧道下穿国道进洞技术研究

Research on Portal Excavation Technology of Shallow-buried Tunnel with Sandy New Loess Crossing Under the National Road

结合蒙华铁路武家坡隧道施工实例,通过建立三维计算模型,模拟分析了各工况下结构受力和沉降变形.通过对超长管棚精确控制,提高了围岩的稳定性;采用调整锁脚锚管参数、拱脚支垫及大拱脚等措施加强了拱架稳定性;使用大型湿喷机和湿喷工艺保证了初期支护强度;通过微台阶工法并“早成环”,进一步控制了隧道及国道沉降变形,实现了安全、质量、工期、成本有效控制和管理.该进洞技术克服了传统分部开挖法效率低、风险大等缺点,为类似隧道施工提供参考和借鉴.

Combined with the construction of the Wujiapo Tunnel on the Mengxi-Huazhong Railway,a three-dimensional calculation model was established to simulate the structural stress and settlement deformation under various working conditions.The stability of surrounding rock was strengthened by precise control of the ultra-long pipe roof,the stability of the arch frame was strengthened by adjusting the parameters of lock foot anchor pipe,arch foot cushion and increasing arch foot.The strength of the initial support was ensured by using the wet spraying process of large-scale concrete robots,the deformation of the tunnel and the national roadway was further controlled through micro-stepping method and timely looping,the safety,quality,construction period and effective control on construction and management were realized.The entering tunnel technology overcomes the shortcomings of traditional partial excavation methods,such as low efficiency and high risk,it could provide reference for similar tunnel construction.