| Summary: | To address loess–mudstone tunnel damage resulting from mudstone swelling induced by water absorption in cold regions, model experiments and numerical simulations were employed to study the tunnel surrounding rock pressure distribution and the stress characteristics of support structures during mudstone swelling at the tunnel base. The findings reveal that the base uplift of the tunnel leads to a rapid stress increase on the arch, and the self-supporting of the interface is insufficient, causing uneven stress distribution on the tunnel. The stress peak value at the bottom of the outer arch is 30.8% of that at the inner side. The internal force of the tunnel lining at the arch crown is the largest. The compressive stress appears at the arch feet, while the tensile stress appears at the outer side of the lining. The bending moments of the inverted arch are larger than those of the arch shoulders and arch crown. The left arch shoulder and arch bottom are primarily subjected to negative bending moments, and the maximum values are about −500 kN·m and −400 kN·m, respectively. The left side of the inverted arch is first to crack, and two main cracks then appeared at the left and right arch shoulders, respectively. The formation and development of the longitudinal cracks in the arch induced by water absorption cause the inverted arch bulge failure. This study helps understand the damage mechanism of the loess–mudstone tunnel in cold regions.
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