ABSTRACT
Varying sleeper support (e.g. seat stiffness) influences the load distribution of the track. Consequently, this might result in locally accelerated ballast and substructure deterioration, including mud spot development.
A vehicle-track-subgrade modelling workflow has been developed to investigate the interaction between its elements. The comprehensive approach incorporates track irregularities, vehicle dynamics, varying sleeper support and complex ballast and soil modeling, including ballast contamination.
Measurements have been conducted at two track sections with known subgrade problems, including a former and possibly reoccurring mud spot. Based on these measurements, calibration and validation parameters for the models are derived, as a case study. Individual rail seat stiffness values could be identified with an iterative approach, using strain and deflection measurement data and a finite element model.
The presented study demonstrates that the identified high variation in rail seat stiffness at the former mud spot leads to individual sleepers with significantly increased load transmission to the ballast. It also highlights the limitation of the loaded geometry, as measured by track recording cars, to reflect the rail seat stiffness variation.
