破碎围岩偏压隧道合理施工方法研究

Research on Reasonable Construction Technique of Unsymmetrical Loading Tunnel in Crushed Rock Mass

破碎围岩段偏压隧道施工时,较多采用双侧壁导坑法,预留核心土对在开挖过程中隧道的围岩变形和支护受力有很大影响,对隧道围岩稳定性起着至关重要的作用.针对重庆境内的某浅埋偏压隧道在施工中的合理工法和安全性保证问题,系统比较分析了上下台阶法施工和预留核心土施工对隧道围岩的应力场、位移场、塑性区和支护结构内力影响.通过计算结果表明,预留核心土施工具有明显的优点,其不但减小了隧道围岩的净空位移,控制了塑性区的发展,而且改善了支护结构的受力,使其更加趋于均匀合理.研究成果与现场施工实际相吻合,为偏压破碎围岩隧道开挖实践提供了理论分析依据.

The method of double-sides-wall drift is usually adopted when unsymmetrical loading tunnel is excavated in weak surrounding rock, and the core rock is a quite important factor to the displace- ment, stability of the surrounding rock mass and the internal force of supporting during excavation. Basing on the problem of reasonable technique and ensure security in LiChuan unsymmetrical loading tunnel construction, the author analyzed the impact of rock mass stress field, displacement field, plas- tic zone and supporting structure internal force of benching tunneling method and keeping core soil tunneling method. The results showed that the latter method was more excellent than the first one, it not only reduces the displacement to tunnel and controlling the plastic zone development of surround- ing rock, but also ameliorates the strain field of supporting structure and making it more symmetrical or reasonable. The calculation is consistent with the fact of construction in--situ, which is the basis of theoretic analysis for unsymmetrical loading tunnel opening in crushed rock mass.