Dynamic Influence of Gap Height of CA Mortar on Track Structure Under Mixed Traffic Conditions

For CRTS I prefabricated slab tracks used in mixed passenger-freight railway, the gap between the CA mortar and the track slab is a common disease. In order to analyse the influence of the gap height of CA mortar on the dynamic response of the track structure, a vertical coupling model of CRTS I slab track with gaps between CA mortar and track slab is established based on the vehicle-track coupling dynamics and the substructure modal superposition method. Firstly, the self-vibration characteristics data of the track component sub-structure, which was calculated by ANSYS, was inputted into SIMPACK, and the track components were connected through a force element to form the track system. Then, the train and rail subsystems were coupled via data transmission of the displacement and force between the nodes of the wheel-rail contact surface and flexible rail. The results show that with the increase in gap height, there is a significant increase in the dynamic displacement of the rail, vibration response of the track slab, and the dynamic stress of the CA mortar. For CRH380, when the gap height was increased to 1.0 mm and 2.0 mm, the rail displacement increased by 0.24 mm and 0.27 mm, respectively. At the same time, the vibration levels of the slab increased by 21.0 dB and 21.7 dB at a frequency of 25 Hz, and the maximum dynamic stress of the CA mortar at both ends of the gap reached 0.2 MPa. Thus, when the height of the gap exceeds 1.0 mm, the influence of the gap on the dynamic response of the track structure tends to be gentle. However, for SS7E, when the gap height was increased to 1.0 mm and 2.0 mm, the displacement of the rail increased by 0.48 mm and 0.66 mm, respectively. Simultaneously, the vibration level of the slab increased by 15.5 dB and 19.4 dB at a frequency of 8 Hz, and the maximum dynamic stress of the CA mortar at the ends of the gap reached 0.24 MPa and 0.36 MPa, respectively. Thus, when the height of the gap exceeds 1.0 mm, there is still a considerable increase in the influence of the gap on the dynamic response of the track structure.