Ground vibrations induced by the passage of double-line trains in underground tunnels

Abstract

Subway systems consist of double lines to transport passengers in the outbound and inbound directions. The existing prediction models for subway-induced vibrations ignored the superimposed effect caused by the successive passage of double-line trains. This study develops a computationally efficient method to simulate ground vibrations during the simultaneous passage of double-line trains in underground tunnels. An analytical model is applied to calculate the transfer function of a track-tunnel-ground system in a multi-layered half-space. Two alternative designs of tunnels in a double-line subway system are considered, which are a double-track tunnel and twin single-track tunnels. By introducing the relation between two different moving frames of reference, a fully coupled solution for the train-track-tunnel-ground system that considers the dynamic interaction between the double-line trains is proposed. The numerical results indicate that the simultaneous passage of double-line trains induces a significant superimposed effect of ground vibrations. The superimposed effect can increase the vertical velocity in the one-third octave spectrum by up to 5 dB, and the running RMS value by up to 40% under the same track roughness. The ground vibrations from one double-track tunnel are more than 30% higher than those from two single-track tunnels due to the passage of the single-line train and double-line trains.