Transient effects of high speed trains crossing soft soil

To reduce the environmental impact (in terms of visibility and noise) it is desirable to construct inter-urban high-speed rail lines with small embankments. However, these small embankments tend to be flexible and on soft ground track-soil bending waves may result in significant transient train-induced soil deflections. These deflections in the permanent way could, in turn, have a major effect on ride quality and also on maintenance costs. A variable frequency inertial vibrator and a series of geophones have been used to examine the response of soil both with and without a rail. The measured soil responses have been used to predict soil model parameters, which are introduced into analytical models in order to predict bending waves in the track/embankment system. The consequent displacements are highly dependent on the speed of the train. This maximum deflection was also found to be dependent on the amount of damping in the system. For all reasonable assumptions the amount of damping present is insufficient to limit deflection to tolerable magnitudes. Thus, the theoretical models can indicate suitable restrictions on train speeds for particular track conditions.