Fatigue damage analysis of ballastless slab track in heavy-haul railway tunnels

A ballastless slab track, which is commonly used in the track structures of heavy-haul railway tunnels, was analysed based on field measurement data of the Fuyingzi Tunnel on the Zhangtang Railway. In accordance with the measured data, the dynamic load thresholds and distributions on the surface and bottom of the ballastless slab track were investigated. A fatigue damage analysis of the ballastless slab track was performed based on the dynamic load time–history curve. The results show that the ballastless slab track can accomplish train load attenuation and reduce the dynamic load from heavy-haul trains by 47.22% from the surface to the bottom. In addition, the distribution at the bottom of the ballastless slab track exhibited a triangular shape, and the dynamic load threshold at the line centre accounted for 78.67% of that at the track position. Meanwhile, the distribution at the surface was saddle-shaped; the dynamic load threshold at the track position accounted for 79.55% of that at the line centre position. The fatigue damage of the ballastless slab track was analysed effectively by combining the measured data and the linear fatigue damage theory. Moreover, the accuracy of the calculation results was verified based on the measured dynamic stress of the ballastless slab track structure. The dynamic action of the train load led to more-concentrated damage to the track bed, and the damage occurred earlier than that in the ordinary line. The axle load was the primary influencing factor of the track bed fatigue damage, and the damage mainly occurred in the track position. These results provide a theoretical basis for performing stress analysis and designing parameters for ballastless slab tracks in heavy-haul railway tunnels.