Modelling stress distribution in substructure of French conventional railway tracks

Many studies were conducted on the modelling of stress distribution of soil foundations based on the elastic theory or uniformly spread hypothesis, but few works focused on the modelling of dynamic stress distribution in railway substructures. In this study, field monitoring was performed at Vierzon, France, using two embedded stress sensors. Dynamic stress data were recorded during train passages at different speeds, from 60 km/h to 200 km/h. Note that the Vierzon site involves a conventional line that is characterised by the presence of an interlayer soil, sandwiched between the ballast layer and the subgrade. The recorded data was firstly used to verify the existing models currently used in practice, revealing the advantages and drawbacks of such models. Then, based on the theory of stochastic stress diffusion in particulate media, a modified load spread model was developed. Comparison with the recorded data shows the relevance of the proposed model. In particular, significant effect of modulus ratio bewteen two adjacent layers on stress distribution was evidenced.