Interface fatigue behaviour of railway track system Type II slab ballastless track subjected to thermal load variations: an experimental study

Environmental temperature significantly affects the interlayer interface performance of CRTS II slab ballastless tracks, yet its influence on fatigue behaviour remains insufficiently understood. This study investigated the fatigue performance of composite specimens consisting of track slabs, cement asphalt (CA) mortar and concrete base under different temperatures and stress ratios. Fatigue tests were conducted to evaluate deformation characteristics, damage evolution and failure mechanisms at the interface. The results indicate that interface fatigue damage progresses through four stages: non-destructive behaviour, crack initiation, crack propagation and final fracture. The fatigue separation displacement history exhibits three phases—slow growth, stable growth and rapid growth—which account for approximately 10%, 70% and 20% of the total fatigue life, respectively. Both high- and low-temperature conditions substantially reduce fatigue life by 85-90%, with low temperatures causing more severe deterioration. A three-dimensional model describing interfacial crack growth rate was developed, capturing fatigue separation behaviour and predicting interface fatigue life under varying environmental conditions.