台阶法在超大断面浅埋偏压隧道中的应用研究

Study of Application of Bench Method to Shallow-buried Asymmetrically-pressured Railway Tunnel of Super-large Cross-section

为探索台阶法在超大断面浅埋偏压隧道施工中的可行性,以蒙华铁路石岩岭隧道为研究对象,对台阶法和传统分部开挖法进行比选,提出三台阶临时仰拱+竖向支撑的开挖工法,并采用MIDAS有限元软件建立地层-结构模型,对施工各阶段隧道-围岩体系的应变-应力进行模拟分析,以判断开挖过程的结构风险。对台阶法施工过程中出现的拱顶沉降大、初期支护出现裂缝、爆破对软硬不均地段的影响和地表土体开裂等问题进行分析并提出相应的对策,现场实施效果表明:台阶法能满足石岩岭超大断面浅埋偏压隧道施工安全的要求,且具有施作技术简单、高效快捷的优点,可为类似工程施工提供参考。

The feasibility of bench method to shallow-buried asymmetrically-pressured tunnel of super-large cross-section is studied by taking Shiyanling Tunnel on Menghua Railway for example. Firstly,the three-bench excavation method to temporary invert and vertical support pillar is selected by comparing bench method to traditional partial excavation method; and the structure stability is analyzed by software MIDAS so as to guide the tunnel construction. And then,the problems encountered during construction,i. e. large settlement of crown top,fissures of primary support and the ground and the influence of blasting on tunnel deformation in hard-soft heterogeneous ground are analyzed; and relevant countermeasures are adopted. The site application results show that the above-mentioned method with advantages of easy operation and high efficiency is feasible to Shiyanling Tunnel. The study results can provide reference for similar projects in the future.