浅覆新黄土隧道微台阶法修建技术

浅覆新黄土隧道洞口地段一般采用CD法、CRD法等分部开挖法施工,存在临时支护拆除量大、大型施工机械设备不便开展作业、施工工效较低等问题。依托蒙华铁路黄土隧道工程,提出以微台阶开挖、湿喷机械手快速支护、仰拱快速封闭成环为核心的快挖快支快成环微台阶法修建技术,并以蒙华铁路张裕2#隧道为例,采用数值模拟方法对采用微台阶法时隧道初期支护变形、围岩塑性区、初期支护结构内力及安全系数等进行分析,验证该方法的合理性。对蒙华铁路全线新黄土隧道施工的监控量测数据、资源投入和施工进度等进行分析,结果表明:大跨度浅覆新黄土隧道采用微台阶法施工,初期支护变形收敛小,便于大型机械作业,综合施工进度达到45~67.5 m/月,能极大地提高施工工效,节约工程造价。

Construction Technology of Micro Bench Method for Shallow covered New Loess Tunnel

The partial excavation methods, i.e. CD method and CRD method, are usually adopted in portal section construction of shallow covered new loess tunnel. But many problems, i.e. large amount of temporary support dismantling, unusable large construction machinery and low working efficiency, restrict the tunnel construction. The micro bench method, takes the micro bench excavation, rapid primary support by wet jet manipulator and rapid inverted arch ring closure as the cores, is proposed by taking loess tunnels on Menghua Railway for examples. And then the tunnel primary support deformation, plastic zone of surrounding rock and internal forces and safety coefficient of primary support structure of Zhangyu #2 Tunnel are analyzed by numerical simulation method, so as to verify the rationality of micro bench method. Finally, the deformation monitoring data, resource investment and construction schedule of loess tunnels on Menghua Railway are analyzed. The analytical results show that by adopting the micro bench method, the primary support deformation is small, the footage of 45-67.5 meter per month is achieved; large scale construction machinery is available; the construction efficiency is improved greatly; and the construction cost is reduced.