Study on Dynamic Response Mechanism of Double‐Track Parallel Tunnels Under Seismic Loading

Earthquake‐induced tunnel damage poses a significant threat to tunnel serviceability. To investigate the dynamic response of double‐track parallel tunnels under seismic loading, this study employs numerical simulations to analyze their behavior. The results show that the circumferential distribution of additional stresses along the tunnel lining exhibits different patterns. Specifically, the additional stresses are notably elevated at the 90°, 180°, and 270° positions of the tunnel lining, whereas they are relatively minimal at the 0° position. The maximum additional stress is observed at the 180° position. In addition, the seismic stress amplification factor induced by P‐waves is markedly higher within the range from 0° to 180° along the tunnel lining. In contrast, the seismic stress amplification factor induced by S‐waves is more pronounced at the 45°, 135°, 225°, and 315° positions, with the affected regions exhibiting an X‐shaped distribution. With increasing burial depth, seismic‐induced additional stresses gradually attenuate. At shallower depths, the influence of P‐waves on the tunnel remains insensitive to input wave frequency, whereas the effect of S‐waves is frequency independent, with higher frequencies generally imposing greater stress on the lining stresses. Furthermore, the seismic stress amplification factor varies with tunnel spacing. Under S‐wave excitation, seismic effects diminish as the tunnel spacing increases.