Mechanical behaviours of CRTS-II ballastless tracks in high-speed railway under thermal loading

Ensuring the high-temperature deformation of CRTS-II ballastless tracks be small is critical for operational safety. This study presents a comprehensive theoretical and experimental investigation into the mechanical behaviors of longitudinally connected track slabs under thermal loading. Corresponding fitting calculation formulas for the critical temperature are proposed. Results reveal that the bonding strength at the CA mortar interface significantly influences the critical temperature, arch amplitude, and wavelength—each increasing linearly with bond strength. When the initial arch amplitude or the proportion of mortar gap increases, the critical temperature decreases exponentially. Comparing the CA mortar softening and non-softening effects, the maximum difference in critical temperature is 16.81°C, corresponding to decrease of 29.35%, the maximum difference in arch amplitude and wavelength are 46.34 mm and 6.87 m, respectively, corresponding to increases of 145.76% and 25.18%. These findings establish a theoretical basis for optimizing design and maintenance strategies of track in extreme temperature environments.