Improving Ballasted High-Speed Railway Track Design for Reduction of Vibration Levels and Maintenance Needs

It has been proven that cyclic loading induced by the circulation of trains at very high speeds (higher than 300km/h) results in important track vibrations progressively amplified in a repeated process leading to the deterioration of track geometric quality and an unwanted increase in track maintenance needs and track life cycle costs. Having this as concern, the present paper focuses on a numerical model of dynamic train/track system which was built to correctly predict train/track dynamic response not only instantaneously but also in a long-term perspective. That is, the same tool enables to access vibration levels in a specific type of track as well as to evaluate track settlement evolution throughout millions of cyclic train passages. This paper starts to describe the numerical model on its: original approach for modeling train/track system with low computing time; extensive validation process with real experimental measurements from several high-speed tracks in Europe; innovative implementation of long-term estimations of plastic deformations accumulation. Moreover, the article shows results from simulations of different track design solutions testing certain specific elements and materials, and how their interaction in a multi-element system will confer the ensemble of the track certain dynamic properties that would enhance its performance. The following track solutions are here evaluated: softening railpads, applying under sleeper pads or using bituminous subballast as an alternative to granular subballast. Finally, critical analyses on the results enable to draw recommendations on ballasted high- speed track design improvements aiming track vibrations mitigation and its maintenance needs.