Evaluation of seismic response of tunnels near slope surfaces and performance of anti-seismic measures

In valley areas, tunnels are commonly constructed near slope surfaces. The seismic behavior of the tunnel near a slope surface is less understood, especially under the combined effect of the geostatic stress and the seismic load. In this research, a boundary integral equation method is developed to analyze the seismic response of the tunnel near a slope surface. The effects of the canyon on the dynamic response of the tunnels with two cross-section shapes under the SV waves at different frequencies and different incident angles are analyzed. Numerical results indicate that the canyon has a manifest intensification effect on the acceleration and stress of the lining within a lower-frequency range. The effectiveness of two typical anti-seismic measures in improving the anti seismic performance of the tunnel near a slope surface is also evaluated. The results indicate that the isolation layer can successfully improve the stress state of the circular tunnel, and it will intensify the tensile stress in the lining of the horseshoe tunnel. When the surrounding rock is strengthened, although the compressive stress in the lining of the circular or horseshoe tunnel decreases, the tensile stress increases.