In situ experimental study on high speed train induced ground vibrations with the ballast-less track

Many conveniences and efficiencies have been brought to the passengers with the rapid growth and application of High Speed Train (HST), especially in China. However, the vibrations induced by HST can cause adverse influences on the surrounding environment, which arouses increasing concerns from researchers and governments. In this paper, in-situ HST generated ground vibrations were measured in the embankment, culvert, viaduct and transition sections of Beijing-Shanghai high speed railway (HSR) in China. The acceleration responses of the free field in three directions (x, y, z) were recorded with a train operation speed of around 250-350 km/h. The characteristics of the three directional free field responses in time and frequency domains are then be acquired. Moreover, the variations of vibration amplitude and its vibration level with the distance from the track centerline and train speed are investigated, respectively. Ground dynamic impact coefficient (GDIC) and ground remaining dominant frequency (GRDF) are first introduced and defined to identify the ground vibration performances. It is found that the vertical acceleration response is typically the largest in the near field, while in the far field the largest one is the transverse acceleration response. When a culvert or viaduct is included, the longitudinal vibration would be dominant in the near field. Typically, an obvious vibration amplification zone can be observed in the field around 20 m due to the wave interference. In all four measurement scenarios, the dominant frequencies of the free field are typically n times the characteristic frequencies, which have a strong relation to the train's geometry dimension and unevenness of the rail. The first dominant frequency of the free field is generally determined by the distance between wheelsets, bogies and the ground fundamental frequency. Some useful recommendations are also provided in this paper and the results are valuable for validating numerical prediction of HST induced vibration and ground-borne vibration mitigation.