针对高原铁路某隧道超长、深埋、高能地质可能引发的高地应力岩爆、软弱围岩(大)变形等问题,通过案例对比、经验总结和技术分析等方法全面分析该隧道TBM在防岩爆、控变形和防坍塌等方面存在的主要问题,并依据各类问题的防控机制提出相关技术思路。总体认为,充分利用TBM自身的施工特点和相关防控措施,并对TBM进行针对性设计及施工技术创新,可以克服该隧道的局部不良地质,具体包括: 1)TBM针对性设计包括合理设置刀盘扩挖长度和护盾长度,加大护盾强度和防护范围,提升超前支护和应急支护能力等; 2)高应力岩爆地层施工要坚持分级防控,主动控制与被动防护相结合; 3)在高地应力软岩地层要坚持抗放结合,注重连续快速掘进和及时支护; 4)在深埋破碎地层要坚持稳掘强护,注重超前加固、及时支护和回填注浆等,以保持循环推进。
A significant
length, large buried depth, and high stresses in the surrounding geological
strata of a plateau railway tunnel may induce rockburst and large deformations
in weak rocks in high groundstress areas. In this paper, the
major challenges associated with rockburst, deformation, and collapse
prevention for a tunnel boring machine(TBM) are comprehensively analyzed using
comparisons with previous projects, practical construction experience, and
technical analyses. Suitable countermeasures are proposed. Generally, the full
understanding of the construction project characteristics, TBMtargeted design, and TBM technical innovations are the key
considerations. These include the following: (1) TBMtargeted
design includes a suitable cutterhead expansion and shield length, shield
strength enhancement, shield protection range enlargement, and advance support
and emergency support strengthening. (2) Adopting hierarchic, active, and
passive prevention and control methods for rockburst in high groundstress areas. (3) Focusing stress resistance and release on areas
with soft rock strata with high ground stress and providing continuous and
rapid excavation and timely support. (4) Emphasizing stable excavation, advance
reinforcement, timely support, and backfill grouting in deeply buried broken
strata.