The amplification effect of river valley topography on seismic response of a tunnel near the valley: simulated by boundary element method

Many tunnels are inevitably built near valley terrain, which greatly amplifies the seismic response of the tunnel. This paper considers the interaction between valley terrain and tunnels, proposes a high-precision indirect boundary element method (IBEM) for simulation, and verifies the correctness of the method. The impact of factors such as incident wave type, incident frequency, and distance between the tunnel and the valley on the seismic response of the tunnel is then analyzed in detail. The numerical analysis demonstrates that the stress of the tunnel can be amplified by approximately twice when the distance between the river valley and the tunnel is 10m due to the scattering and coherence effects of seismic waves. However, when this distance is greater than 50m, the presence of river valleys has little effect on the stress of the tunnel. The stress at the right shoulder of the tunnel and the displacement amplification effect on the valley slope is significant compared to other areas. The findings of this study provide theoretical guidance for the seismic fortification and disaster avoidance of tunnel structures near river valleys.