Dynamic behavior and cumulative deformation analysis of ferronickel slag-clay mixtures under cyclic loading

Ferronickel slag, an industrial byproduct, shows potential as road subgrade filler after modification. However, its permanent deformation accumulation under cyclic traffic loads may cause rutting and cracking, compromising long-term performance. Existing studies mainly focus on static mechanical properties, while dynamic response and deformation mechanisms remain insufficiently explored. To fill this gap, this study explores the dynamic properties and cumulative deformation behavior of ferronickel slag-clay mixed fillers through a series of experiments. First, dynamic backbone curves for the mixture were obtained through semi-sinusoidal cyclic loading dynamic triaxial tests and scanning electron microscope (SEM) analysis, allowing the determination of the optimal clay content and compaction degree. Next, single-stage cyclic loading dynamic triaxial tests were performed to obtain the relationship between cumulative plastic strain and cycle numbers, while examining the effects of dynamic stress ratio and confining pressure on the cumulative deformation behavior. A cumulative plastic strain prediction model was developed, incorporating the number of load cycles, dynamic stress level, and confining pressure. Finally, based on shakedown theory, a critical dynamic stress prediction model for the mixture was proposed, and the results were used to revise the S. Werkmeister stability determination criteria. The findings reveal that the optimal structural stability and dynamic strength of the ferronickel slag-clay sample occur at 35% clay content and 96% compaction. The cumulative plastic strain increases with the dynamic stress ratio and decreases with confining pressure. The developed cumulative plastic strain prediction model accurately reflects the deformation characteristics of the filler, and the critical dynamic stress prediction model provides a theoretical basis for calculating the dynamic stability of ferronickel slag-clay subgrade fillers.