A COMPARISON BETWEEN THE PERFORMANCE OF FLOATING-SLAB TRACKS WITH CONTINUOUS AND DISCONTINUOUS SLABS IN REDUCING VIBRATION FROM UNDERGROUND RAILWAY TUNNELS

摘要

Vibration from moving trains in underground tunnels has a significant impact on nearby buildings and their occupants. Vibration is generated in tunnels and propagates to nearby buildings where it can be perceived directly as vibration of walls and floors or indirectly as reradiated noise. The problem is of a major concern for sensitive buildings near railway tunnels such as concert halls and recording studios. One of the effective measures to reduce vibration from underground railways is the use of floating-slab tracks. These tracks are constructed by supporting the rails on a slab with a large mass. The slab is supported via soft resilient elements on the track bed. The slab can be cast in-situ resulting in a track with continuous slab and it can be constructed in discrete pre-cast sections leading to a track with a discontinuous slab. In this paper, the performance of tracks with continuous slabs in reducing vibration from underground tunnels is compared to that of tracks with discontinuous slabs. A numerical model is presented and employed for each type of tracks. A wheel-set moving with a constant velocity on a track with rail irregularity is used in both models. The model of the continuous slab has one periodicity arises from the rail irregularity at a given wavenumber. The model of the discontinuous slab has a second periodicity arises from the repeating units of slabs. A model of a tunnel embedded in an elastic half space is used to calculate the transfer functions of the tunnel and ground. The forces at the wheel-rail interface are calculated and compared for both types of tracks. The power spectral density of vibration in the far field is also calculated for both types of tracks and pronounced peaks in the response are discussed.