Full assessment of railway ballast and sub-ballast aggregates in terms of mechanical, thermal, and dynamic performance

Abstract The increasing demands associated with higher train speeds and heavier axle loads require ballast materials with well-characterized mechanical, durability, and deformation properties. While numerous studies examine individual aspects of ballast behaviour, few provide an integrated assessment linking small-scale index properties with large-scale cyclic performance. This study addresses this gap through a comprehensive experimental program evaluating four lithologies commonly used or regionally considered for railway infrastructure: olivine, limestone, basalt and phonolite. The program includes particle shape characterization, abrasion and impact resistance tests, freeze–thaw and magnesium sulphate soundness assessments, permeability measurements, modified Proctor and California Bearing Ratio testing, and large-scale cyclic triaxial tests to determine resilient modulus, Poisson’s ratio and permanent deformation. The results reveal clear lithological distinctions. Basalt exhibited the most favourable overall performance, with the lowest abrasion losses, high specific gravity, resilient modulus values exceeding 1500 MPa at 150 kPa confining stress, and permanent deformation below 2 mm after 10,000 load cycles. Olivine showed advantageous particle geometry and high density but recorded the highest Micro-Deval losses and notable freeze–thaw degradation. Limestone displayed moderate mechanical performance and limited durability, whereas phonolite exhibited acceptable stiffness and bearing capacity but higher water absorption and freeze–thaw susceptibility. Permanent deformation followed the logarithmic model with R² values between 0.83 and 0.93, and deformation accumulated primarily within the first 1000 cycles. By integrating thermal, mechanical, and dynamic evaluations within a single framework, this study provides performance-based insights for more reliable, sustainable ballast selection. The findings support a rigorous trade-off analysis between conventional and regional high-performance lithologies, ultimately contributing to improved long-term maintenance strategies for ballasted railway infrastructure.