Numerical Modeling of High-Speed Train/Track System to Assess Track Vibrations and Settlement Prediction

The circulation of trains at very high speeds (higher than $300\mathrm{k}\mathrm{m}/\mathrm{h}$) leads to important vibrations in the track and its environment. Concerning the track behavior, this dynamic cyclic loading conduces to the deterioration of its geometric quality, which progressively amplifies the vibration levels in a repeated process, leading to an increase in track lifecycle costs. Within this framework, this paper presents a dynamic numerical model that was built with this concern and was consistently validated with real experimental measurements at different maximum speeds, also above $300\mathrm{k}\mathrm{m}/\mathrm{h}$. The implementation in the model of long-term estimations of plastic deformations accumulations is described and highlighted. The influence of increasing train speeds in the level of vibrations reached in different types of tracks may be evaluated, as well as the track settlement evolution along the track and throughout millions of cyclic train passages. Different design alternative solutions are simulated: softening railpads, placing under-sleeper pads or ballast mats, or using bituminous subballast as an alternative to granular subballast. Critical analyses on the results obtained in the paper enable one to draw recommendations on the mitigation of track vibrations and maintenance interventions, that is, on the possible improvements to be made to ballasted high-speed track design considering its maintenance needs.