Effects of complex interaction of Rayleigh waves with tunnel on the free surface ground motion and the strain across the tunnel-lining

Abstract

The effects of complex interaction of Rayleigh waves with lined and unlined tunnels on the free surface ground motion and longitudinal and shear strains across the tunnel-lining are documented in this paper. The effects of depth and diameter of tunnel and the embedding sediment on the amplification and de-amplification of ground motion are studied in detail. The effects of depth of tunnel and the embedding sediment on the longitudinal and shear strains across the tunnel-lining are also studied in detail. The seismic responses of various tunnel models were simulated using a fourth-order accurate staggered-grid viscoelastic P–SV-wave finite-difference algorithm. The analyses of the simulated results reveal that the amplification/de-amplification caused by the tunnel increases with the decrease in depth of tunnel. Ground motion amplification was obtained between the source and the tunnel. An increase in amplification/de-amplification pattern with increase in S-wave velocity in the embedding sediment and the diameter of the tunnel for a fixed depth was obtained. It is concluded that the chances of failure of tunnel-lining due to strain may be just opposite side of the incoming Rayleigh wave in case of a shallow tunnel ( 25 m deep).