Acceleration of soft ground with tunnels near soft-hard strata interface: Longitudinal shaking

Current aseismic design has seldom considered the effect caused by underlain tunnels. Previous studies of this issue have already dealt with the situation of tunnels embedded in homogeneous soil under transverse seismic excitation. It would be essential to explore the ground response pattern when tunnel crossing the region of soft-hard strata, commonly in river crossing tunnels. A shaking table test of scaled tunnel-strata model was conducted to investigate the influence of the tunnel on the acceleration response of the ground. In this test, harmonic excitations with different frequencies and intensity levels were input from the shaking table, in the direction along the tunnel axis. By comparing the ground acceleration response of the free-field model and the tunnel-strata model, amplification of the ground acceleration caused by tunnels was found with both frequency and intensity of excitation.