An Extended Perspective on the Disturbed State Concept for Rubber–Mixed Waste Material Considering Modulus Degradation under Cyclic Loading

Railway substructure materials bear a large number of repeated loads resulting in progressive shear failure with permanent deformation. For constructing new railway substructures or restoring existing ones, stabilizing granular materials with rubber offers both financial and environmental benefits. This paper discusses the deformation and deterioration behavior of rubber–mixed granular waste materials under cyclic triaxial loading by adopting volumetric strain–based disturbed state concept and proposing a degradation index based on the change of resilient modulus. The proposed hyperbolic model effectively captures the volumetric strain behavior of rubber–mixed granular materials under cyclic loading. An extension of the disturbed state under cyclic loading is described in this study to examine the behavior of rubber–mixed granular waste materials, specifically the coal wash-rubber crumb mixtures and the rubber-intermixed ballast system. The results categorize three distinct degradation zones in relation to a newly introduced disturbance function and a degradation index.