DEVELOPMENT OF A SIMPLE TRANSFER FUNCTION OF PERMANENT DEFORMATION FOR ASPHALT TRACK FOUNDATION

초록

Permanent deformations are often the controlling load-associated distress governing the performance of Hot Mix Asphalt (HMA) layer. Asphalt formation used as trackbed foundation for providing greater vertical bearing capacity onto track structure is investigated in this study. Permanent deformation in asphalt trackbed foundation can be generated by increasing number of load repetition due to train traffic increases, causing track irregularity. Therefore, a design criterion for consideration of permanent deformation must be included in construction of distress model for this kind of track structure. In this study, a specially prepared HMA trackbed foundation layer has been constructed in a small prismoidal chamber and tested using a repetitive axial loading device to simulate live track loadings. In this study, a new concept of track compliance and equivalent modulus of track section are proposed. Using the measured permanent deformation data by performing loading-unloading test in the prismoidal chamber, a relation between permanent deformation and track compliance is generated. For design purpose, a simple transfer function based on permanent deformation of critical value (5mm) and track compliance, C, for the asphalt track can be provided successfully in this study. The resilient and permanent deformation characteristics are going to be analyzed from field test and full-size loading tests with different track sections in the following studies so that a full design transfer functions can be developed finally in the future. The final design model for permanent deformation will be adapted in design of the asphalt trackbed foundation.