INVESTIGATION OF USING A BITUMINOUS SUB-BALLAST LAYER TO ENHANCE THE STRUCTURAL BEHAVIOR OF HIGHSPEED BALLASTED TRACKS

Abstract

This paper evaluates the most suitable thickness of both asphalt and ballast layers to improve
the conventional high-speed ballasted tracks. The work was conducted by designing asphalt mixture using the
Marshal method in the laboratory and using the ANSYS software to evaluate the best thickness of both the
ballast and asphalt layer to minimize vertical deformations and corresponding stresses. The results of the
numerical analysis showed that the minimum deformations and stresses for a track containing a bituminous
sub-ballast system are lower than the deformations and stresses for a conventional system when the thickness
of the ballast layer was 250 mm. However, when the thickness of the ballast layer was 300 mm, the vertical
deformation increased when the asphalt layer thickness increased. This theoretical analysis proved that a track
that consists of 250 mm ballast and 120 mm bituminous sub-ballast layers enhances the structural behavior of
the high-speed ballasted tracks.