Ground vibration from freight railway: environmental impact and potential mitigation measure at propagation path.

The freight train-induced vibrations and noise generate increasing environmental problems owing to its heavier axle loads and longer pass-by duration. To develop useful mitigation measures, the vibration characteristic induced by this type of rail transportation needs to be better learned. In the present work, firstly, the in situ measurements were carried out on two railway lines which were used for mixed freight and passenger trains. Both the track vibrations and ground vibrations resulted from different train types were measured and compared. Then, based on the dominant frequencies of ground vibrations from experimental results, the mitigation measure of periodic piles was proposed as a mitigation measure by impeding propagation. The periodic theory of solid-state physics was introduced and three-dimensional (3D) finite element (FE) simulation was employed to analyse the vibration reduction performance of periodic piles, while the attenuation zone (AZ) of the piles was also calculated. The measurement results indicate that the freight train can generate a larger level of vibrations on both the track structure and ground at the near field, especially below 10 Hz. Even though the speed of freight trains is as low as 40-55 km/h, the vibration exposure level (VEL) is higher than normal passenger trains (80-90 km/h) and EMU trains (120 km/h). The simulation results show that the proposed solution of installing periodic piles at the propagation path raises the positive influence on vibration reduction.