DESIGN CHARTS FOR ASPHALT TRACKBED FOUNDATION WITH CONSIDERATION OF TEMPERATURE VARIATION

초록

Design charts for asphalt trackbed foundation are developed in this study that can consider performance design parameters including elastic modulus of the material of each layer, layer thicknesses, wheel load size, design velocity and MGT (Mega Gross Tonnage). In order to develop design charts for the asphalt trackbed foundation, three dimensional finite element analyses are performed broadly. Especially, temperature effect on modulus of asphalt mixture can be considered by adapting SUPERPAVE temperature prediction model and cumulated temperature data from meteorological stations. Thus, elastic modulus variation with different temperature level can be considered in finite element structural analysis of the asphalt track. Using the computed tensile strains at the bottom of the asphalt layer used as the trackbed foundation and vertical strains at the top of the subgrade soils, a design life can be computed based on the modified design criteria offered by AI (Asphalt Institute) which is provided originally for asphalt pavement. Parametric studies are performed with different input values of elastic modulus of the material, layer thickness, wheel load size and MGT. By superposition of each obtained design life for an asphalt track section, design charts can be constructed with different input parameters. Finally, by analyzing the obtained design charts again, a simple design table can be obtained for practical purpose