Evaluation of dynamic stress behavior in CRTS III slab track subjected to differential subgrade settlement and temperature gradient

The CRTS III slab track operates in a complex environment where differential subgrade settlement (DSS) and temperature gradient (TG) significantly affect its mechanical properties and geometry, thereby impacting track durability and train safety. A train-CRTS III slab track-subgrade coupled dynamic model considering the contact nonlinearity is developed. Taking the state of track structure caused by DSS and TG as the initial condition, the combined effects of DSS and TG on the dynamic stress behavior in CRTS III slab track under moving train are explored. Results show that DSS causes sharp peaks in initial mechanical responses within the DSS region, while TG induces cyclic fluctuations across the entire track. Under combined loads, the moving train induces the greatest amplification in fastener compression force (increasing by 5.51 times), and the least amplification in base plate (BP) tensile stress (increasing by 0.11 times), relative to their initial values. The tensile stress in BP is primarily influenced by DSS, while the pressure stress on BP is predominantly affected by TG, and other indicators are influenced by both DSS and TG. DSS and TG significantly affect track structures, with composite slab failing when DSS exceeds 12.5 mm, BP failing when DSS exceeds 11 mm, and fasteners and subgrade requiring both high DSS and TG for failure. This research provides critical insights into track design and maintenance strategies to ensure the stability and safety of high-speed railway systems under dynamic loading conditions.