Study on the Influence of Subway Train Load on Environmental Vibration Based on a Vehicle–Track–Tunnel–Site Coupled Analysis Model

With the rapid development of rail transit, environmental vibrations caused by subway vehicle loads have garnered increasing attention. This study employs a three-dimensional finite element–infinite element coupling method to establish an integrated numerical model of the vehicle–track–tunnel–ground coupled system. The vehicle loads are obtained through the simulation of a physical vehicle model, incorporating the effects of track irregularities as excitation sources. Based on this model, the dynamic response characteristics of subway-induced vibrations within structural components and geological layers are systematically investigated. The results show that the vertical vibration response in the surrounding ground is most pronounced, with the vertical acceleration distribution following the pattern: tunnel bottom > tunnel crown > tunnel sides. Furthermore, high-frequency vibration components attenuate rapidly within one tunnel diameter. As vehicle speed increases, the vibration response in the surrounding ground significantly intensifies, indicating that dynamic effects are more pronounced under high-speed operation. Meanwhile, the vibration responses in far-field regions tend to converge. This study also finds that an acceleration amplification zone appears in the low-frequency band (0–5 Hz) during vibration propagation. Additionally, the near-field tunnel response exhibits energy concentration around 35 Hz before attenuation, which is significantly higher than the dominant frequency after propagation to the far field. These findings provide important insights for understanding the propagation mechanisms of subway-induced vibrations and offer a solid basis on which to develop effective vibration control strategies.