Sleeper Contact Modelling in Asphalt Overlayment Trackbeds

This study targeted the mechanics of asphalt overlayment trackbeds – a ballastless track type that mandates special wide-base sleepers equipped with a geotextile at the bottom. The objective was to develop an analytical model for quantifying how a geotextile and its compressibility properties influence the contact stress distribution at the sleeper-geotextile-asphalt interface. A nonlinear-hardening Winkler spring-bed was utilised to represent a geotextile, a rigid beam was utilised to represent a sleeper, and the pavement system was treated as an elastic half-space. Based on a parametric investigation of the new model it is concluded that the insertion of a geotextile at the sleeper-asphalt interface considerably affects the vertical stress distribution. The presence of a geotextile is shown to produce a more uniform stress distribution and eliminate excessively high contact stresses that would have developed near the sleeper perimeter. It is also shown that geotextile compression adds extra vertical flexibility to the track system with an order of magnitude similar to that of common rail pads. The developed model can handle realistic geotextile compressibility properties as well as any sleeper geometry; its analytical nature provides relative ease of replication for subsequent design and analysis.