Incompatible thermal deformation of interlayers and corresponding damage mechanism of high-speed railway track structure

In the service period, the instability of ballastless track bed are mostly related to the damage of interlayers which are mainly resulted from the incompatible thermal deformation of interlayers. The temperature field within the ballastless track bed shows significant non-uniformity due to the large difference in the materials of various structure layers,leading to a considerable difference in the force bearing of different structure layers. Unit Ballastless Track Bed(UBTB)is most significantly affected by temperature gradient. The thermal deformation of interlayers within UBTB follows the trend of ellipsoid-shape buckling under the effect of the temperature gradient, resulting in a variation of the contact relationship between structure layers and a significant periodic irregularity on the rail. When the train travels on the periodically irregular rail, the structure layers are locally contacted, and the contact zone moves with the variation of the wheel position. This wheel-followed local contact greatly magnifies the interlayer stress, causes interlayer damage,and leads to a considerable increase in the bending moment of the track slab. Continuous Ballastless Track Bed(CBTB)is most significantly affected by the overall temperature variation, which may cause damage to the joint in CBTB.Under the combined action of the overall temperature rise and the temperature gradient, the interlayer damage continuously expands, resulting in bonding failure between structural layers. The thermal force in the continuous track slabs will cause the up-heave buckling and the sudden large deformation of the track slab, and the loss of constraint boundary of the horizontal stability. For the design of a ballastless track structure, the change of bearing status and structural damage related to the incompatible thermal deformation of interlayers should be considered.