Longitudinal Seismic Behavior of Cracked Tunnels Crossing Faults: Insights From a Fracture‐Aware Modeling Approach

ABSTRACT Tunnel linings crossing active fault zones are critical vulnerabilities in underground infrastructure due to long‐term seismic and tectonic stresses. Focusing on cast‐in‐place linings, this study develops an analytical framework for evaluating the longitudinal seismic response of cracked tunnels traversing fault fracture zones. The lining is modeled as a multi‐cracked Euler‐Bernoulli beam supported on three distinct Pasternak elastic foundations. A generalized solution for bending deformation under arbitrary crack configurations is derived using Laplace transforms, which is then validated through benchmark cases and 3D extended finite element (XFEM) simulations incorporating concrete damage plasticity. Parametric studies reveal that crack‐induced stiffness reduction creates localized deformation singularities, where deeper cracks amplify a stress‐relief effect, suggesting that engineered settlement joints could strategically mitigate dynamic loads. Paradoxically, increasing lining bending stiffness elevates internal force magnitudes by up to 31.3%, challenging conventional reinforcement strategies. Furthermore, while wider fault zones monotonically increase deformation and bending moments, they induce a non‐monotonic shear response that peaks at the fault‐hanging wall interface. The axial influence range of seismic effects also expands with fault width. This framework provides a physics‐informed tool for optimizing crack‐tolerant designs in fault‐crossing tunnels, effectively balancing deformation accommodation and load redistribution under seismic excitation.