Analytical Study of Optimal Ballast Thickness on Ballasted Track with Asphalt Subballast Layer

This paper focuses on analyzing the thickness correlation between the asphalt subballast layer and the ballast layer. For this purpose, based on the results of full-scale static and dynamic load tests with and without an asphalt subballast layer, FEM analysis was performed using the ABAQUS program. A sufficient correlation was confirmed by comparing the full-scale experimental results, such as track displacement and subgrade pressure, with the FEM analysis results of KENTRACK, etc.; based on this, various analyses were attempted using various ballast layer thicknesses and asphalt subballast layer thicknesses as variables. As a result, when the ballast layer thickness was reduced in a sub-ballast layer using an asphalt subballast layer(50 mm), the roadbed pressure was reduced by about 7 to 18% compared to the case of applying the existing standard ballast layer thickness. In the case of track stiffness, the performance was equivalent to that of the standard ballast layer, within 101.2-102.4%; and in the case of the ballast layer allowable contact pressure, it was about 30% lower than the allowable contact pressure. Therefore, as a conclusion of this study, when installing an asphalt subballast layer under a ballast layer, the ballast layer thickness can be reduced.