The study of train-track interaction and resulting ground vibrations generally (and often exclusively) focuses on the vertical direction. This study explores the directional characteristics of train-induced ground vibration, based on in-situ measurements conducted at different locations in the Netherlands with two subsoil types-sand and clay, and different substructures, for a set of operational parameters. Triaxial accelerometers were installed at the ground surface along the track, in a spatial configuration capturing both near-field (or non-radiating) and far-field (or radiating) contributions of the ground response in terms of particle motion. Through statistical and comparative analyses of field-measured data, the results show a strong dependence of the dominating directions of particle motion on the ground composition (soft or still soils) and therefore also on the cross-sectional track geometry in terms of substructure and embankment. These findings highlight the relevance of paying due attention to both normal and in-plane (longitudinal and lateral) components of train-track interaction and ground particle motion in the modeling, mitigation and prediction of train-induced vibration hindrance. ... Read more

The relationship between subgrade settlement and rail deformation remains unclear, and the impact of subgrade settlement on dynamic responses of the ballasted track, as well as on the running safety and comfort of high-speed trains, has not been adequately quantified. To address such deficiency, a three-dimensional (3D) numerical model of train-ballasted track-subgrade coupled system considering spatial differential subgrade settlements was established. An innovative iterative algorithm was proposed to determine the real-time track-subgrade contact, enabling the analysis of resulting track irregularities and train-induced vibration. The results show that the number of unsupported sleepers increases with greater settlement amplitudes and shorter settlement wavelengths, while spatial differential subgrade settlement significantly affects wheel-rail interaction. Track structures located at the settlement center area on the side with less settlement, as well as those at the settlement boundary area on the side with greater settlement, are more susceptible to damage. These areas also exhibit higher dynamic vertical subgrade stress, thus aggravating differential settlement. The findings could provide theoretical basis and technical guidance for improving high-speed railway operation and maintenance practices. ... Read more