Seismic Response of Rectangular Tunnels by Centrifuge Testing and Numerical Analysis

A series of dynamic centrifuge tests performed at the geotechnical centrifuge facility of IFSTTAR in Nantes, on rectangular model tunnels embedded in dry sand is presented. The effect of salient model parameters such as soil-to-tunnel relative flexibility, soil-structure interface properties and characteristics of the input motion is explored. Representative test cases are modelled by means of rigorous finite-element configurations of the coupled soil-tunnel system, accounting for the non-linear soil response and soil-tunnel interface behaviour under seismic loading. Numerical results are compared with experimental data in terms of soil and tunnel acceleration and tunnel deformations. The validated numerical models are then used to evaluate the accuracy of simplified analysis methods. Experimental and numerical results reported herein indicate among others: (i) a rocking deformation mode coupled with a racking distortion of tunnels during seismic shaking and (ii) a significant effect of the soil-tunnel interface properties and soil non-linear behaviour on the tunnel response. Simplified seismic design methods may, under certain conditions, provide a reasonable framework for the analysis at least at a preliminary stage.