Track-bed mechanical behaviour under the impact of train at different speeds

This paper aims to study the influence of train speed on the mechanical behaviour of track-bed materials based on field data recorded at a representative site of the conventional French network. Capacitive accelerometers and soil pressure gauges were installed in track-bed layers. The Intercity train was selected to perform this study as it is the most frequent train running on this site. In total, 1790 records corresponding to Intercity train passages were taken into account, with train speeds ranging from 60 to 200 km/h. The vertical strains of different layers were estimated by integrating the signals of accelerometers installed at different depths. It is observed that when train speed increased in the considered range, the traffic loadings, in terms of dynamic stress transmitted to track-bed materials, were amplified about 10%. However, the vertical strains of track-bed materials were also amplified by 2 in the same range of speeds. These amplifications appear mainly in shallower layers. The stress-strain amplitude ratios for all the recorded trains were calculated to analyse the evolution of resilient moduli (Mr) of track-bed materials. It is found that Mr of interlayer soil decreased by approximately 25% when train speed increased from 60 to 200 km/h.