大断面黄土隧道微台阶开挖工法施工稳定性研究

Construction Stability of Large-Section,Shallow-Buried Loess Tunnel by Micro-Bench Method

为解决软弱黄土隧道在开挖过程中发生的变形、渗水和坍塌问题,以天恒山隧道为工程背景,提出一种适用于富水软弱黄土地层浅埋大断面隧道微三台阶开挖工法。采用数值模拟与现场监测相结合的方法,验证微三台阶法对富水软弱黄土地层浅埋大断面隧道开挖时的适用性。研究结果表明:1)施工过程中采用微三台阶法开挖,围岩变形及支护受力得到较好的控制,隧道拱顶沉降和净空收敛值分别为34.6 mm和17.2 mm;围岩最大应力为102.5 kPa;初期支护封闭成环控制约11 m,三台阶七步约为18 m。2)通过监测数据与数值模拟结果对比分析,初期支护模拟数据略大于现场实测数据,但整体变化趋势基本一致,说明了软弱黄土地层中微三台阶工法控制围岩稳定性的有效性。

Challenges such as deformation,water leakage,and collapse occur when excavating soft loess tunnels.Therefore,a micro-three-bench method is proposed for the large-section,shallow-buried Tianhengshan tunnel in water-rich loess strata.Then,numerical simulations and field monitoring are employed to validate the applicability of the micro-three-bench method.The research results demonstrate the following:(1)The micro-three-bench method effectively controls the surrounding rock deformation and support force,resulting in 34.6 mm tunnel crown settlement and 17.2 mm clearance convergence.The maximum stress of the surrounding rock is 102.5 kPa;the primary support closed ring is controlled at 11 m,and the three-bench and seven-step are controlled at 18 m.(2)The simulated primary support is slightly larger than the monitored data.These data present a similar trend,indicating the effectiveness of the micro-three-bench method for stabilizing the surrounding rocks of tunnels in soft loess tunnels.