Seismic Response and Design of Rectangular Tunnels

The paper presents a series of dynamic centrifuge tests that were carried out at the geotechnical centrifuge facility of the University of Cambridge, on a rectangular model tunnel embedded in dry sand. The tests are simulated by means of finite-element analysis of the coupled soil-tunnel system and the numerical results are compared and validated with the experimental data. Additional numerical analyses are carried out to examine the effects of crucial parameters on the tunnel response, such as soil-to-tunnel relative flexibility and soil-structure interface characteristics. The calibrated numerical models are then used to validate the accuracy of simplified design methods. The interpretation of both the experimental and numerical data reveals, among others, a rocking deformation mode of tunnels during seismic shaking coupled with the racking distortion and a significant effect of the soil-tunnel interface properties and soil yielding response on the amplitudes and distribution of the seismic earth pressures, the dynamic soil shear stresses as well as the dynamic internal forces of the tunnel lining. Simplified design methods, under certain conditions and assumptions, may provide reasonable and comparable results to the full dynamic analysis.