Stress–Strain Analysis of Heavy Haul Rail Track with Steel Slag Ballast by Laboratory Tests and Numerical Simulations

Abstract

The resilient response of the ballast layer is a key aspect for stress–strain behavior of rail track lines. This paper presents part of an extensive research that has been evaluating the possibility of using, with operational benefits, Inert Steel Aggregates for Construction (ISAC) as heavy haul railroad ballast material. Stress–strain analyses were performed by finite element method (FEM) whose pseudo-elastic parameters for nonlinear constitutive laws were obtained from resilient modulus tests by Method B from European Standard EN 13,286-7 (CEN: Unbound and hydraulically bound mixtures—Part 7: cyclic load triaxial test for unbound mixtures. EN 13,286–7, Brussels (2004) [CEN (European Committee for Standardization) (2004) Unbound and hydraulically bound mixtures—Part 7: cyclic load triaxial test for unbound mixtures. EN 13286-7, Brussels]) for ‘higher stress levels’ carried out under scaled down ballast specimens in a ratio of 1:2.5 from ballast standard AREMA N. 24 (AREMA, Manual for railway engineering, vol I–IV. Lanham (2015) [AREMA (American Railway Engineering Maintenance-of-way Association) (2015) Manual for railway engineering, vol I–IV. Lanham, USA]). The numerical simulations were carried out at two loading levels (32.5 and 40 t/axle) increased by dynamic impact coefficient of 1.4. The results showed that the structure with ISAC ballast has lower levels of vertical displacements and moments on the rails and was able to concentrate more stress in the ballast layer decreasing slightly the stress level on the top of platform in comparison with what was observed for the structure with a well-known-granite ballast, commonly used in rail track lines around the world.