Influences of piles on the ground vibration considering the train-track-soil dynamic interactions

High-speed trains can induce significant amplification of dynamic responses of components in railway tracks especially when the train travels at the so-called 'critical speed'. Based on a critical literature review, most previous studies with respect to train-track-soil interactions have merely been focused on the simplified natural ground vibrations. Accordingly, there exists no investigation into the influences of piles on the ground responses despite the fact that the pile-reinforced ground improvement has been widely adopted in soft soil regions for high-speed railway with slab track systems. In order to highlight the influences of piles on ground vibrations, a 3D fully coupled train-track-soil model has been developed based on the multi-body simulation principle, finite element theory, and perfectly matched layers method using LS-DYNA, in which the dynamic material properties of slab tracks have been adopted. This model has been validated by comparing its results of ground vibrations and train-track interactions with field-test results. This is thus the world's first to investigate the critical speeds of slab-track railway with natural and pile-reinforced ground improvement. The dynamic displacements, vibration velocities, and dynamic stresses of soils with natural and pile-reinforced grounds have then been evaluated under normal and critical train speeds. The accelerations of car body and dynamic impact factors with the increasingly train speed have also been presented. The piles influences on the wave propagations in the soils have been highlighted. The novel insight from this study provides a new and better understanding of ground vibrations in high-speed railway systems using slab tracks in practice.