Effects of Railway Ballast on the Sound Radiation From the Sleepers

Regular paper

Xianying Zhang

Dynamics Group

Wednesday 3 june, 2015, 11:40 - 12:00

0.1 London (90)

Railway ballast is an important component in the railway system. It is a layer of stones located below and around the sleepers; it supports the track vertically and provide lateral stability. The gaps between the stones make it behave acoustically as a porous material, absorbing noise to some extent. In addition ballast can itself vibrate and reradiate noise during train pass by. It is not clear, however, to what extent ballast contributes to noise and how much its mechanical and acoustical properties modify the radiation of the sleeper and the rail. This paper focuses on quantifying the influence that ballast has on noise, particularly the sleeper radiation. A one-fifth scale model of the track is adopted to conduct acoustic and vibration measurements on ballast. Two different scaling factors are adopted to reproduce the ballast properties: for the acoustic absorption the scaling factor for the stone dimensions is 1/sqrt(5), without modifying the geometrical scale of the problem, while the mechanical behaviour is correctly reproduced by scaling the stones at 1/5. Analytical models will be proposed to predict ballast vibration and absorption. Finally, the effects on the noise radiation from a scaled concrete sleeper are compared with the experimental results.

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