Shaking table test on a segmental tunnel crossing soil-rock interface under transverse sinusoidal excitations

This paper investigates the seismic characteristics of a segmental tunnel crossing soil-rock interface by 1 g shaking table tests. Materials of the scaled physical models are selected to achieve a ground-tunnel relative stiffness consistent with that of the prototype, and a refined model tunnel is manufactured to imitate the features of actual segmental tunnels. A free-field model is tested beforehand to characterise the dynamic responses of the model ground using transfer function, acceleration amplification ratio and dynamic stress–strain relationship. For the ground-tunnel model, the emphasis is placed on the soil-structure interaction in the soil-rock strata. The discrepant responses of the tunnel are firstly revealed by the acceleration responses. Then, the sectional deformations of the tunnel are analysed. While negligible in the rock stratum, they become much greater in the soil deposit. Due to the spatial variation caused by the abrupt changes in ground conditions, significant joint extensions are observed near the soil-rock interface. Based on the test data, a simplified analytical model for calculating the joint extension is developed and verified, thus shedding light upon the mechanisms of this deformation mode.