Effects of track properties on ground vibrations generated by high-speed trains

Increase in speeds of railway trains is usually accompanied by higher levels of generated ground vibrations, which are especially large if train speeds exceed the velocities of Rayleigh surface waves in the ground. Therefore, it is vitally important to consider possible methods of protecting the built environment against intensive ground vibrations associated with high-speed trains. The present paper investigates the effects of some geometrical and physical properties of the track, i.e., those of track bending waves and distance between sleepers, on railway-generated ground vibrations. It is shown that the effect of track bending waves may cause increase in amplitudes of ground vibrations generated by trains travelling at speeds higher than the velocities of Rayleigh surface waves in the ground (trans-Rayleigh trains) it the train speeds approach the minimal phase velocity of track bending waves. This implies that tracks with low minimal phase velocities of bending waves should be avoided. The reduction of a sleeper period results in decrease of generated ground vibrations for trains travelling at speeds below the velocities of Rayleigh surface waves in the ground (sub-Rayleigh trains). This effect can be used for reduction of generated ground vibrations in selected parts of the rail route. For trans-Rayleigh trains, the reduction of a sleeper period does not affect the vibration levels. Theoretical results are illustrated by numerically calculated frequency spectra of ground vibrations generated by single axle loads travelling at different speeds and by TGV, Eurostar and British high-speed trains.