Dynamic Response of the Entrance Structure of an Elliptical Mountain Tunnel under the Action of SH Waves

Generally, the surrounding rock at the entrance of a mountain tunnel is loose, and the entrance has more slopes due to topography, which causes the tunnel entrance section to be easily destroyed under an earthquake. Based on the established slope model with a single free surface, this paper adopted the elastic wave theory to derive the analytical solution of the strain at the entrance of the mountain tunnel when the SH wave is incident perpendicularly to the bottom of the tunnel; besides, the factors affecting strain were also analyzed. The tangential strain curve at each point of the entrance section takes the centre of the elliptical tunnel as the centre of symmetry, forming symmetry between the left and right sides and mirror symmetry between the top and bottom sides. Then, large-scale shaking table model experiments were conducted to model the actual working conditions, and the correctness of the analytical solution was verified. The research can provide a theoretical reference for the seismic design of the entrance section of the high-speed railway tunnel and greatly improve the understanding of its seismic response.

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