Dynamic Response of a Tunnel Lining Under the Coupled Influence of Near-Field Effects and an Elastic–Slip Interface

This paper presents an analytical solution for near-field cylindrical P-wave scattering by a circular tunnel. A comprehensive elastic–slip interface model is incorporated to capture localized discontinuous deformations and frictional sliding. Employing the wave function expansion method and Graf’s addition theorem, the dynamic stress concentration factor (DSCF) of both soft and stiff linings is systematically investigated. The results reveal that near-field wavefront curvature severely amplifies stress concentration on the illuminated side, degenerating into a plane-wave response only when the dimensionless source distance exceeds 50. Furthermore, within the parameter range considered, the imperfect interface exhibits a dual “flexible barrier” effect heavily influenced by impedance matching: it tends to act as a seismic isolator that reduces the DSCF for stiff linings, but can weaken boundary confinement and exacerbate stress concentration for soft linings. These findings provide crucial theoretical insights for the blast-resistant design of underground structures.