The Influence of Subgrade Subsidence on Train Track Dynamic Interaction

This paper reports results from a numerical model to calculate subgrade settlement
in railway tracks due to repeated dynamic loading. The trains are modelled as rigid
body 2-axle carriages on two layers of springs. The track is modelled as a beam
supported on three layers of springs. Permanent deformation of the subgrade layer is
calculated on the basis of a power law assumption. Patterns of dynamic forces are
calculated on a smooth track and on a track subject to an initial subgrade ‘pothole’.
The latter is shown to grow with repeated loading and to change the mean patterns
of applied force.