Laboratory and numerical analysis for enhanced ballast performance: towards sustainable railway track pavement design

The physical and mechanical characterization of rock materials is a crucial step for their applicability as a railway ballast layer. However, most of the standardized tests for such characterization do not have direct application for the ballast layer design and the normative limits take into account only the origin of the rock material, ignoring the axle load factor and the lifespan for which the railway project is designed. This study aims to demonstrate the importance of characterizing materials in this process, through laboratory tests (physical and mechanical) and finite element modeling with four different rock materials as ballast, applying the results to obtain a reduction in the use of stone materials, aiming an optimized and sustainable concept for new railway projects. The effects of ballast thickness on subgrade stresses are analyzed in terms of subgrade bearing capacity and permanent deformation of geotechnical materials. The results show that variations in the ballast’s resilience modulus between 294 and 115 MPa have minimal influence on the subgrade’s vertical stresses, but that reductions of 10 cm in the thickness of this layer can increase subgrade stresses by up to 20%. Furthermore, an increase in the number of non-cubic particles can lead to greater permanent deformations, which can reduce the period between track maintenance cycles. Finally, the analysis showed that the Micro-Deval test can be considered an interesting method for the mechanical characterization of ballast and can be used to estimate its lifespan.