Rail Track Performance with Different Subballast Solutions: Traffic and Environmental Effects on Subgrade Service Life

This paper discusses the effect of using different subballast solutions in the overall performance of the substructure on the basis of a methodology suitable to account for the effects of rail traffic loading and environmental actions in the hydro-thermo-mechanical performance of the subgrade over its service life. The mechanistic design of the different railway track configurations is first analyzed through a three-dimensional finite-element (FE) model, accounting for the adequate modeling of the sleeper-ballast interface. Then, a two-dimensional FE hydro-thermic analysis is developed to assess the effect of the different solutions in the performance of railway trackbed layers resulting from environmental effects (atmospheric actions and phreatic level variations) when modeling superficial drainage systems that enable the runoff of excess rainwater. Results from the mechanistic and hydro-thermic analysis were combined to predict the long-term deformational behavior of the subgrade. The proposed solutions with bituminous layers showed a better performance than the granular-only design concerning the substructure predicted service life cycle.