Numerical Simulation Of Ground Vibration Induced By High-Speed Train On Non-Ballasted Railway

Chinese railway realizes a tremendous development nowadays with high-speed railway taking shape, and environmental problem induced by high-speed railway will without doubt affect the normal life of residents nearby. Therefore, it is necessary to carry out research about ground vibration caused by high-speed railway and grasp vibration characteristics and propagation regularity. This paper discusses about ground vibration of non-ballasted high-speed railway in soft soil region. After three parts of summary which is about research method in rail-transit-induced environmental problems, basic problems and environmental problems caused by high-speed railway, a vertical train-track coupled model is established according to vehicle-track coupled dynamics, and two FEM models, containing a2D embankment-foundation FEM model and a3D track-embankment-foundation FEM model, are also established by means of FEM method in ANSYS software. By combining these models above, the investigation is carried out in both2D and3D aspect.First of all, by using the simplified2D embankment-foundation FEM model, ground vibration attenuations of homogeneous elastic half space and layered ground with the harmonic load between0and90Hz are discussed. Results show that vertical ground vibration of homogeneous elastic half space reveals a fluctuating decay under the harmonic load, and the higher the frequency is, the faster the attenuation is. Within a certain distance from the track centerline, ground vibration induced by mid and high frequencies should not be neglected. For layered ground, the fluctuation of the decaying of ground vibration is more severe, and there occurs obvious rebound.On the basis of harmonic response analysis, forces on the surface of subgrade along the track are obtained from the vertical train-track coupled model, and applied onto the2D FEM model to investigate time-domain characteristics, frequency-domain characteristics and propagation behavior of vertical ground vibration acceleration, when the high-speed train is running on non-ballasted track in soft region. The forces are converted to an equivalent force loading on subgrade surface of the2D model according to the plain-strain equivalent methodology, and the equivalent force contains mid-frequencies and high-frequencies. Simulation results show, despite of the differences in time-domain characteristics, the domain frequency is in the mid-frequencies, close to wheelbase-induced characteristic frequency. The time-domain peak values of vertical ground vibration are apparent near the railway, and then become very small with slow attenuation after20m away. Frequency-weighted vertical acceleration level of ground vibration presents a dramatic decrease within30meters, and then gets slower after that.At last, rail fastener loads along the track are achieved using the vertical train-track coupled model, and are applied onto the3D FEM model to investigate the regulation of vertical ground vibration when the high-speed train is running on non-ballasted track. It shows vertical ground vibration displacement can reflect the passage of train at least within50m from track centerline. Vibration displacement along transverse direction can reflect soil characteristics and the effect of pile foundation reinforcement clearly. Vibration velocity and acceleration are respectively the first derivative and second derivative of vibration displacement, thus vibration characteristics is more obvious in the frequency band which contains the wheelbase-induced frequency. Compared with the2D case, both time-domain peaks of vertical vibration acceleration and frequency-weighted vertical acceleration level of ground vibration have the consistent tendency but larger values because of the limitation of model size. Due to the track irregularity, variation of vertical ground vibration displacement, velocity and acceleration along longitudinal direction of the trackline is not homogeneous, but for time-domain peaks of vertical vibration acceleration and frequency-weighted vertical acceleration level of ground vibration, there is a little difference in general. The2D FEM model can somewhat forecast vertical ground vibration acceleration with train passages at speed of350km/h on non-ballasted track, and it also can be used for evaluating human perception.