Fouled Railroad Ballast: Characterization, Mechanical Behavior and Finite Element Method Simulation

The fouled ballast layer is formed due to settlement, tamping, and traffic. This layer has a high fines content and different structural behavior submitted to track load. In addition to losing its draining capacity, there is also a change in rigidity and a decrease in the bearing capacity with degradation. It would be better to avoid having the fouling ballast in the railway pavement; however, the costs of changing the ballast may be unfeasible in the short term. Thus, it is essential to understand the influence of degradation on the mechanical behavior of the ballast. This paper discusses track simulation using the finite element method (FEM), with Resilient Modulus (MR) data from triaxial tests carried out on the fouling ballast, to understand better this layer's behavior related to the stiffness variation. Additionally, the parameters and behavior of other ballast materials are compared with fouled ballast. In this study, mean values of MR were found to be between 49 and 285 MPa for optimal moisture content for fouling ballast. From numerical analysis using Systrain software, the maximum deflection on the track was 5.6 mm, the maximum stress on the rail was 119.15 MPa, and the contact pressure between the sleeper and ballast was 0.147 kPa. Despite being within the limits of the railway standards, these values were obtained at optimal moisture content. This situation is not likely to happen in the field when considering the fouled ballast.