Evaluation of PCC Pile Method in Mitigating Embankment Vibrations from a High-Speed Train

Dynamic response of a railway embankment to a high-speed train is simulated for two cases: the soft ground is improved by cast–in situ concrete pipe (PCC) piles, and the soft ground is not improved. The obtained results are compared to evaluate the effectiveness of ground improvement in mitigating embankment vibration from a high-speed train. The study shows that ground improvement significantly reduces embankment vibration at all considered train speeds ($36–360\hspace{0.17em}\text{km/h}$). The possibility of vibrational resonance when the train speed approaches the critical speed governed by the soft soil is completely excluded. However, vibrational resonance still happens when the train speed approaches the critical speed governed by the embankment material, and this suggests the following implication. Even when the soft ground of a railway embankment system has already been improved, vibrational resonance can still happen at high train speeds. Furthermore, for a given site, each ground improvement scheme results in a different change in the natural vibration properties of the system and hence a different behavior of vibrational resonance. Therefore, besides design issues concerning stability and settlement of the embankment system under static loads, its vibrational resonance behavior is another issue of concern that should be carefully evaluated because it is associated with the operational safety of high-speed trains.