Symmetric and Asymmetric Stress Redistribution in Corrugated Steel–Concrete Composite Tunnel Linings Under Non-Uniform External Pressure

Circular tunnel linings are geometrically symmetric structures, whereas non-uniform external pressure and different steel–concrete layer arrangements may induce asymmetric stress redistribution. To distinguish the axisymmetric response from the asymmetric harmonic response, this study develops an analytical solution for a two-layer corrugated steel–concrete composite tunnel lining subjected to equivalent external pressure. The concrete layer is modeled as an isotropic elastic material, while the corrugated steel layer is represented as an equivalent cylindrically orthotropic material. The governing equations are formulated in polar coordinates under plane-strain conditions, and the solution is obtained by superposing the axisymmetric component and the harmonic component. Perfect bonding is assumed at the steel–concrete interface, where displacement, radial stress, and shear stress are continuous. The proposed analytical solution is verified using finite element models for three cases: a single-layer homogeneous lining under uniform pressure, a two-layer composite lining under uniform pressure, and a two-layer composite lining under non-uniform pressure. The analytical and finite element results show good agreement, confirming the mathematical consistency and implementation accuracy of the proposed formulation. Based on the verified solution, the effects of layer arrangement, corrugated steel stiffness ratio, and burial depth are investigated. The results show that the corrugated steel layer carries the dominant hoop stress in both layer arrangements. The inner corrugated steel arrangement may be more relevant to internal strengthening of existing tunnels, whereas the outer corrugated steel arrangement provides a useful reference for new composite linings dominated by external ground pressure. Increasing the stiffness ratio transfers more hoop stress to the steel layer and reduces the elastic stress and displacement responses of the concrete layer, although improvement becomes less significant at large stiffness ratios. Increasing burial depth mainly amplifies the response magnitude without changing the overall symmetry pattern. The proposed solution provides a closed-form benchmark for evaluating symmetry-related stress redistribution in corrugated steel–concrete composite tunnel linings within the linear-elastic range.