Comparative analysis on dynamic behavior of two HMA railway substructures

A numerical analysis using a finite element program was performed on three structures: hot mix asphalt (HMA) reinforced trackbed (RACS-1), HMA directly supported trackbed (RACS-2), and traditional Portland Cement Concrete (PCC) slab track (SlabTrack). Although the comprehensive dynamic responses of RACS-1 were similar with SlabTrack, HMA layer can positively affect the stress distributions. In particular, the horizontal stresses indicate that the resilience of RACS-1 was improved relative to SlabTrack. In addition, HMA reinforced substructure has the capacity to recover the residual vertical deformation. The effective depth for weakening dynamic loadings is mainly from 0 to 2 m, this being especially true at 0.5 m. The results from the analysis show that HMA is a suitable material for the railway substructure to enhance resilient performance, improve the stress distribution, weaken dynamic loading, and lower the vibration, especially at the effective depth of 2 m. The HMA constructed at the top of the stone subbase layer allows the vertical modulus a smooth transition. In terms of the comprehensive dynamic behaviors, RACS-1 is better than SlabTrack, while the results for RACS-2 are inconclusive and require further research.

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