Dynamic Response of Tunnels to Obliquely Incident P- and S-Waves Using Domain Reduction Method

Underground tunnels play a vital role in modern infrastructure, often requiring rigorous seismic assessment to ensure structural safety and serviceability. Seismic wave interaction with tunnels, particularly under oblique P- and S-waves incidences, induces complex deformation patterns and stress distributions. This study investigates the seismic response of tunnels to obliquely incident P- and S-waves using the domain reduction method (DRM). The DRM is a computationally efficient numerical approach developed specially for localized seismic analysis of critical structures. By incorporating oblique wave angles and interaction between the soil and the tunnel structure, the displacement potentials and deformation fields are derived enabling accurate modeling of seismic behavior. The proposed methodology integrates a three-dimensional numerical framework that accounts for wave propagation in heterogeneous media and the tunnel–soil interaction. Parametric studies are conducted to evaluate the influence of wave inclination, frequency, and soil–structure interaction on longitudinal deformations of tunnel and stress concentrations. Results indicate that the oblique waves exacerbate asymmetrical stress distributions and deformation patterns, which are often underestimated in the traditional analyses wherein only vertical or horizontal wave propagation is considered. These results highlight the importance of accounting for oblique seismic wave effects in tunnel design to provide the increased safety and resilience. The detailed insights into the structural response under realistic seismic conditions offer practical guidelines for engineers and researchers involved in the response analysis of underground constructions. These findings underscore the necessity of adopting advanced modeling techniques, such as DRM, for accurate seismic analysis and effective design of underground infrastructure.