Numerical and experimental assessment of damping behaviour in slag–rubber granular layers for railway trackbeds

The integration of industrial by-products such as steel slags and recycled tyre rubber into the granular layers of railway trackbeds represents a sustainable strategy to improve both mechanical efficiency and vibration mitigation. Within the scope of the ECO_RORAIL project, this study aims to advance the understanding and modelling of the dynamic and dissipative behaviour of these unbound mixtures. A three-dimensional numerical framework is adopted to analyse the stress and strain field induced by train loading and to support the interpretation of complementary laboratory tests. The experimental component focuses on characterising the resilient and energy-dissipative response of slag-rubber mixtures under cyclic loading, providing the basis for the definition and calibration of appropriate constitutive parameters. The combined numerical and experimental results are used to explore how small increments of rubber incorporation influence stiffness, damping ratio, and the overall vibration transmission through the trackbed layers. The study contributes to establishing reliable approaches for incorporating alternative materials in railway design, promoting circular economy practices while maintaining structural and dynamic performance standards. The outcomes are expected to support future developments on model calibration, design criteria, and field validation within the ECO_RORAIL framework.