Subballast role in train-track structure interaction in high speed line

the needs to reduce maintenance costs in high speed-railways lines leads researchers to examines much more closely train-track-superstructure interaction. Layer materials in superstructures are very important for the behaviour of track under dynamic loads: they have to be selected very carefully on the basis of both viscous-elastic and resistance caracteristics. With referench to superstructure with ballast and sub-ballast layers, the advantages of making sub ballast layers with very high modulus materials have been considered. A dynamic model of the superstructure is developed in this paper by adopting the finite element model; the analysis has been conducted using the software MSC/Nastran. Power Spectral Density function of track irregularities has been adopted as input of the dynamic system vehicle-track-superstructure. As a result a negligible increase in dynamic overloads due to high complex modulus of modified asphalt concrete in sub ballast have been found.