Experimental study on fatigue performance of ballastless track with concrete-filled tube connected double-block sleepers

The new concrete filled steel tube (CFT) connected double-block sleeper overcomes the problems existing in the truss reinforcement double-block sleeper, such as complex production and manufacturing, easy corrosion in storage, and easy cracking in operation, which can be widely used in high-speed railway and urban rail transit ballastless track structure. In order to test the fatigue performance of CFT double-block sleeper ballastless track structure, a full scale ballastless track structure segmental model was casted in situ using eleven prefabricated CFT double-block sleepers. The fatigue tests were carried out on the damping track with rubber vibration isolation pad and monolithic cast in situ track segments. The fatigue damage characteristics were revealed for these two kinds of track structure. The distribution and evolution of strain and deformation were analyzed for track structure subjected to static load after typical fatigue loading cycles.The results show that after 5 million times of fatigue loading at the level of 1.5 times the static axle load, there is no visible cracks in the concrete structure of ballastless track with CFT double-block sleepers in the damping segment and the cast in situ segment. The overall working performance of the sleepers and the cast-in-place track bed is good, and the fatigue performance meets the specification requirements. During the static loading test, the transverse strain value of concrete at each measuring point of the track structure increases approximately linearly with the increase of load, and the maximum tensile and compressive strain value is far less than the corresponding limit strain value of concrete, which is in good working condition. The middle layer of track bed slab of the cast in situ segment is in the state of overall tension, and it can be seen that the joint working of the track bed and the base plate is realized by setting the interlayer connecting reinforcement. During the fatigue test, the vertical displacement value of the track structure at measuring point gradually increases with the increase of the static load. The magnitude of the displacement is small, which meets the requirements of the specification. The vertical displacement value and its change rate of the damping track section are greater than that of the cast-in-place track section. The research results can provide reference for similar research and engineering application of ballastless track with concrete-filled tube connected double-block sleepers. © 2024, Central South University Press. All rights reserved.