Studies on vibration generation and transmission in tack and ground from high-speed trains

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The present investigation focused first on the dynamic behavior of the track and the wave motions in the nearby ground where the train speed approaches the wave velocity in the underlying ground. Then, the vibration mitigation is considered by a rationally designed countermeasure of limestone columns beneath the track in view of the wave motions at site. For illustrative example, the case of X-2000 high-speed train at the West Coast in Sweden is demonstrated with some comparison with the field measurement.The present modeling of the track-ground system lead an excellent response prediction in comparison with the field measurements. The sleepers' effect on vibration is clarified in the frequency domain : namely, at the low train-speed of 70 km/h they generated the frequencies that are determined by the integer multiplied quotient of train speed against sleepers spacing, however, for 200 km/h the dynamic wave generation more dominates the response so that the sleepers' effect appears almost negligibly small. The velocity component, on the other hand, is greatly affected by the presence of sleepers for the train speed of 70 km/h but not for the 200 km/h. There are different situations we concern for response levels either by displacement, velocity or acceleration. The appropriate engineering judgment should be made on the basis of most involved physical quantities.For controlling of the track vibration the installment of lime-cement columns were made beneath it This worked as the wave impeding barrier and proved to be very effective to reduce the large response displacements for 200 km/h to the very small level for 70 km/h. The visual presentation is demonstrated for easy understanding of the behavior of track and the soil beneath it.