Authors
Eivy Alvarez, Xiaobin Chen 

Abstract
The use of ballasted track in railway construction remains one of the most common techniques internationally, and for such systems, the sub-ballast plays an important role as it provides a solid support and should ensure the functionality of the ballast. However, a common problem with track substructures is that materials slowly deteriorate and break apart due to traffic loading. This causes changes in the geometrical arrangement of particles and clogging of the ballast bed by fine particles thus increasing the cost of routine maintenance needed to restore track alignment. This paper describes the results of an experimental program intended to measure the physical and mechanical properties of polymer-reinforced granular mixtures intended for railway sub-ballast. The main objective is to determine improvements of material behavior when compared to non-reinforced sub-ballast. Polymer-based composite structures have advantages over other materials, especially from the economical, technological and environmental perspectives. For this, investigation several samples of gravel-sand mixtures were prepared using different volumetric ratios of polymer fiber which ranged from 0 to 15%. Samples were tested through large-scale consolidated drained triaxial testing (CDTx). Measured parameters include stress ratios, volumetric ratios, void ratio and rate of dilation. These parameters are important to infer material behavior when used in a larger-scale engineering application. The contribution resulting from this experiment comprises a better knowledge of the physical and mechanical behavior of polymer-reinforced granular mixtures and its applicability to railway ballasts.