A Probabilistic Model of Fatigue Life at the Interface of CRTS II Slab Ballastless Track

The gradual deterioration of interfacial performance in CRTS II (China Railway Track System II) slab ballastless tracks during long-term service can significantly affect structural stability and durability. Existing studies have mainly focused on the fatigue performance of the overall track system and individual structural layers, whereas probabilistic fatigue-life modeling of the interlayer interface remains relatively limited. This study investigates the fatigue life behavior of the track slab-CA (cement-asphalt) mortar interface under cyclic loading. An exponential stress life relationship was combined with a two-parameter Weibull distribution of fatigue life at a specified stress ratio to establish a multi-parameter Weibull-based probabilistic framework that links fatigue life, stress ratio, and failure probability. Push-out and positive tensile fatigue tests were conducted on composite specimens to obtain interface fatigue lives under different stress ratios. Leveraging the multi-parameter Weibull model and experimental data, the L-BFGS-B (Limited-memory Broyden-Fletcher-Goldfarb-Shanno with Box constraints) algorithm was employed to optimize the model parameters and construct a probabilistic fatigue life model. The calibrated model was then used to analyze the fatigue behavior of the slab-CA mortar interface under tangential and vertical loading. The results show that the proposed probabilistic framework provides good agreement with the interface fatigue test data and enables the fatigue-life distribution and failure probability of the interlayer interface to be evaluated under different stress ratios. The findings provide a probabilistic basis for fatigue assessment and durability analysis of CRTS II slab ballastless track interfaces.