Vibration reduction with installation of rail dampers—a case study

Abstract

Measurements of ground vibration were taken in a rail tunnel and cross passage, before and after the installation of rail dampers. In addition to lower in-car noise, measurements indicated an immediate reduction in ground vibration, attributed to the rail dampers. While the most significant observed reduction in vibration was at frequencies above those of interest for ground-borne noise control (16–250 Hz), a reduction in average vibration of up to 9 dB was recorded at 150–200 Hz. This paper summarises the measurement results from two parallel rail tunnels. One of the tunnels includes results with and without rail dampers. Results from the opposite tunnel are used as a control data set. As a shuttle service was in operation at the time of the measurements, the same rolling stock was utilised for both tracks. The Pipe-in-Pipe (PiP) model has been used in an attempt to reproduce the measured change in vibration due to the addition of rail dampers. The initially selected model parameters reproduced the vibration reduction, but predicted it would occur at lower frequencies than indicated by the measurements, i.e. at 100–150 Hz. This simple model with the rail dampers represented as pure masses also suggested that vibration may increase above 160 Hz with the addition of rail dampers, but no increase was seen in the measurements at any frequency. Adjusting the model parameters improved the correlation of the modelled and measured insertion gains. Predictions were then made for the insertion gain on the surface immediately above the rail tunnel, to identify the potential for a change in ground-borne noise. A potential modest reduction in surface vibration in a small frequency range around 160 Hz has been predicted as a result of rail damper installation in a tunnel.