乐西高速大凉山1号隧道平导TBM施工至层状粉砂质泥岩地层时，洞壁围岩松动掉块现象显著，围岩存在较大变形。为探明层状粉砂质泥岩地层TBM施工围岩破坏特征，探讨合适的支护方法，结合现场观测和数值模拟方法研究该地层TBM掘进中围岩破坏过程和围岩稳定性影响因素，并在此基础上开展TBM支护方法研究。结果表明： 1）当围岩露出护盾后变形量值与塑性区范围增大，围岩破坏程度加剧，以锚杆和钢拱架为主的支护结构无法较好地控制围岩变形和塑性区发展，锚杆、钢拱架支护区域是TBM施工洞壁围岩破坏的关键区域； 2）该地层围岩稳定性主要受到围岩层状结构、高地应力和TBM独特的支护方式综合影响。支护优化数值模拟结果表明，在增加锚杆长度、改变喷射混凝土支护方式（分为初喷和复喷）后，围岩变形和塑性区得到控制，围岩破坏模式得到改善，在一定程度上提高了围岩稳定性，采用该方法后现场施工效果良好。
When the tunnel boring machine(TBM) used in
Daliangshan tunnel of Leshan-Xichang expressway bored to parallel
heading No.1 in the layered silty mudstone strata, the surrounding rock
loosened and fell, and large deformation occurred. As a result, to investigate
the damage characteristics of the surrounding rock during TBM construction in
layered silty mudstone strata and explore feasible support methods, the field
monitoring and numerical simulation methods are adopted to study the damage
process and the factors affecting the stability of the surrounding rock in TBM
tunneling in such strata. On this basis, the research of TBM support method is
carried out. The results show the following: (1) The deformation and plastic
zone of the surrounding rock increase after the shield passes by, the damage of
the surrounding rock intensifies, resulting in uncontrollable surrounding rock
deformation and plastic zone development under the support of anchor bolt and
steel arch frame. The protection zones by anchor bolt and steel arch frame are
the key points. (2) The stability of the surrounding rock in such strata is
mainly affected by the combination of the layered rock mass formation, high insitu stress, and the unique support method of the TBM. The numerical
simulation results of support optimization show that after increasing the rock
bolt length and changing the sprayed concrete support method into primary spraying
and secondary spraying, the deformation and plastic zone of the surrounding
rock have been controlled, the damage has been decreased, and stability of the
surrounding rock have been improved, reaching a good construction effect.
