Dynamic assessment of interlayer debonding in high-speed slab tracks using frequency-domain simulation

Interlayer debonding between the concrete slab and CA mortar layer is a critical defect affecting the safety and durability of high-speed railway slab tracks, yet its dynamic effects under realistic conditions remain insufficiently understood. This study presents an efficient frequency-domain vehicle–track–bridge coupling model that achieves a substantial reduction in computational cost, enabling comprehensive parametric analysis across 462 scenarios. Uniquely, the model incorporates measured track irregularities from in-service defected sections, ensuring that simulation inputs closely represent actual field conditions. Through systematic sensitivity analysis, the frequency-domain responses of key components are evaluated to identify diagnostic frequency bands and sensitive monitoring targets for debonding detection. Results reveal that reductions in mortar layer stiffness and increases in debonded length significantly amplify vibration responses, with the carbody, bogie frame, and rail showing the greatest sensitivity in the 40–110 Hz frequency band. Threshold effects are identified, with defects longer than 1.25–1.875 m reliably detected via RMS and correlation coefficients. These findings provide practical guidance for selecting optimal frequency-domain indicators for early debonding detection and condition monitoring in slab track systems, which supports predictive maintenance and enhanced operational safety.