Numerical analysis of ballastless asphalt tracks subjected to dynamic loads

This study presented the results of numerical analyses for a ballastless asphalt track. The asphalt layer was modelled as a linear viscoelastic (LVE) solid that was resting on an unbound granular layer (UGL) simulated as a non-linear (stress-state dependent) elastic medium. The mechanical properties of these layers were calibrated from laboratory element tests. For a given structural arrangement, the model was interrogated under a vertical impulse load to assess the sensitivity of selected responses to temperature and to the initial compaction-induced horizontal stresses in the UGL. It was found that horizontal tensile strains at the bottom of the asphalt layer, vertical stresses below the UGL, and vertical surface accelerations were all very sensitive to temperature level. The vertical surface accelerations were also found to be sensitive to the level of compaction-induced stresses in the UGL. In contrast, the other two responses exhibited a moderate dependency on the latter stresses. The results from this numerical study provide a better overall understanding on the mechanical behaviour of ballastless asphalt tracks.