Rail Restraint Mechanism and Interfacial Longitudinal Mechanical Behavior of Continuous Welded Rail on Ballastless Track

Under the combined effects of complex temperature fields and vehicle loads, the original equilibrium of internal forces within the continuous welded rail (CWR) is disrupted. This leads to highly complex mechanical behaviors at the interface between the rail and its underlying support structure, directly threatening track stability and traffic safety. By introducing a dynamic longitudinal resistance model that real-time responds to the vertical pressure fluctuations of fastener components, a vehicle-track coupled dynamics model is established. The spatiotemporal evolution laws of the track longitudinal resistance and forces under the combined action of train and temperature are systematically investigated, and the motion states of the rail interface are identified. The results indicate that the friction coefficients at the contact interfaces of clip-rail and rail-pad are 0.24 and 0.65, respectively. Wheel-rail impacts induce variations in the vertical pressure of the components, further causing the track longitudinal resistance to fluctuate synchronously with the same frequency. Notably, the impact degree of axle load on the dynamic resistance is significantly greater than that of operational speed. Under vehicle loads, the maximum value and amplitude of the fastener longitudinal force are positively correlated with the train axle load and operational speed, whereas the minimum longitudinal force decreases due to the reverse displacement of the rail. Under the action of temperature gradients, the fastener longitudinal force exhibits a highly symmetrical "bell-shaped" spatial distribution along the track direction, and the fastener longitudinal force is positively correlated with the temperature force gradient. When temperature and vehicle dynamic loads act concurrently, the wheel-rail tangential creep force triggers a sharp increase in the longitudinal force; meanwhile, the pressure within the fastener system escalates, resulting in a synchronous growth of the track longitudinal resistance. Throughout the entire period of train passage, the longitudinal force never exceeds the synchronously increasing dynamic resistance, and the rail interface remains in a micro-motion state. This demonstrates that the vehicle dynamic load does not cause macroscopic sliding at the interface; the interface truly transitions into a sliding state only when the fastener longitudinal force induced by the quasi-static temperature force itself exceeds the static resistance. This study provides a theoretical foundation for revealing the mechanism of longitudinal rail creeping in CWR.