REDUCTION OF RAILWAY INDUCED VIBRATION WITH SOFT FASTENING SYSTEMS FOR BALLASTED TRACKS

Within the scope of the European Project RIVAS (Railway Induced Vibration Abatement Solutions), the vibration mitigation potential of soft fastening systems for ballasted track was investigated through numerical simulations, laboratory tests and real scale measurements. The results of these studies are summarized in this paper. For the numerical simulations, a 2.5 Dimensional methodology is used based on a coupled FE-BE method (the properties of the soil and the track are invariant along the axis of the track). From these simulations, it is shown that soft fastening systems have a low pass filter effect on ground vibration. At the resonance frequency for which the unsprung mass of the vehicle bounces on the track stiffness (around 60 Hz), ground vibration is amplified up to 15 dB. Above this resonance frequency, there is a cut-off effect leading to a mitigation of ground vibration up to 20 dB. For the laboratory measurements, a single sleeper equipped with two pieces of rail is laid in a ballast box. A static load is applied to the rails by a hydraulic jack as the dynamic excitation is provided by a modal shaker. A classical Fastclip system is tested with different rail pads as well as two innovative fastening systems produced by Pandrol: the Vanguard (rail held by its web) and the Vipa Valiant (baseplate and two resilient layers). The laboratory tests confirmed the performances expected from the simulations. Finally, the Vipa Valiant is tested in a commercial track, for three different configurations (different stiffness for the Vipa Valiant system obtained with different rail-pad/baseplate-pad combinations).