为明确软弱围岩条件下高速铁路隧道大断面机械化施工过程中的掌子面稳定性特征，以郑万铁路巴东隧道穿越巴东组紫红泥岩段为工程背景，对隧道揭露的巴东组紫红泥岩开展不同含水率下的三轴试验，揭示巴东隧道紫红泥岩的水-岩软化特征； 在考虑水-岩软化特征的Hoek-Brown强度准则下，构建考虑水-岩软化作用的隧道穿越巴东紫红泥岩地层流-固耦合数值模型，揭示不同地层水位下巴东组紫红泥岩隧道大断面施工掌子面稳定性特征； 最终提出“掌子面喷混凝土+掌子面超前锚杆+超前管棚”的组合式超前加固方案。经过试验和模拟计算，结果表明： 1）随含水量的增加，巴东隧道紫红泥岩的刚度与抗剪强度显著降低，与既有研究揭示的浅表地层紫红泥岩相比，巴东隧道紫红泥岩具有更高的抗剪强度； 2）掌子面后方拱顶沉降、掌子面前方拱顶预收敛、掌子面挤出变形的最大值均随历史水位的升高而增大； 3）根据不同地层历史水位条件下开挖面支护力与挤出变形之间的关系，巴东隧道紫红泥岩掌子面稳定性可以分为A（稳定）、B（短期稳定）以及C（不稳定）3类，对于C类掌子面，采用“掌子面喷混凝土+掌子面超前锚杆+超前管棚”的组合式超前加固措施后，掌子面前后方各项变形最大值可以减小60%～90%。

To investigate the tunnel face stability characteristics of the high-speed railway tunnels during mechanized construction in weak surrounding rocks, a case study is conducted on the Badong tunnel of the Zhengzhou-Wanzhou railway crossing purple-red mudstone of the Badong Formation. The triaxial tests are conducted on such mudstone with different moisture contents to reveal the water-rock softening characteristics. Based on the Hoek-Brown strength criterion, a coupled fluid-solid numerical model is constructed for the tunnel passing through the purple-red mudstone to reveal the stability characteristics of tunnel face under different water levels. A composited advance reinforcement scheme, shotcreting on tunnel face, advance anchor bolts, and advance pipe roof, is proposed. The results reveal the following: (1) With increasing water content, the stiffness and shear strength of the mudstone significantly reduce. The purple-red mudstone revealed from the Badong tunnel exhibits a higher shear strength than shallow strata-revealed one. (2) The maximum settlement of crown behind tunnel face, pre-convergence of crown ahead of tunnel face, and extrusion deformation of tunnel face increase with increasing historical water level. (3) Based on the relationship between the support force and extrusion deformation of the tunnel face under different historical water levels, the stability of the Badong tunnel can be categorized into three groups: A (stable), B (short-term stable), and C (unstable). For Category C, the maximum deformation of the tunnel face can be reduced by 60% to 90% under the proposed reinforcement scheme.