Model Experiment Study of Continuous Track Slab Tension Cracks

To investigate the thermal cracking patterns in continuous ballastless track and verify the rationality of its thermal force determination method, several reinforced concrete specimens were built to model the continuous track slab and base plate which was widely used in China's high-speed railways. Taking into account the key design factors of the continuous track slab, such as concrete grade, reinforcement ratio, rebar diameter, etc., all the specimens were designed as 450 mm long, with an 80 mm×80 mm cross section; and a ribbed rebar of 10 mm diameter was deployed at the center of the cross section. The test specimens were tensioned using the universal testing machine to simulate the development of cracks under the tensile thermal force in the process of temperature drop. The axial force of the specimens and the stress distribution in concrete and reinforcement were recorded before and after cracking. The results show that cracks in specimens during the tensile process were in two states: unstable and stable. Reinforcement and concrete stress was extremely uneven distributed after cracks appear, and reinforcement stress increased to more than 300 MPa at the crack position. The axial force of the specimen would drop suddenly when cracks occurred to the whole section, and the axial force just before and after cracking was higher than or equal to the theoretical cracking axial force of the concrete. For continuous track slab using C40 concrete, more than 0.9% reinforcement should be configured to ensure the safety of the structure. Cracks in track slab should be controlled in unstable stage. As one of the design loads of the continuous track slab, the maximum thermal force load should be calculated using the axial tensile force after cracking.