Deformation characteristics and damage evolution mechanism of interlayer non-coincident contact in double-block ballastless track under cyclic normal loads

Interlayer damage is a significant issue in the lifecycle and operation of ballastless track structures. For the longterm service of ballastless tracks, research must study the deformation and damage evolution of non-coincident contact between the track slab and supporting layer under cyclic normal loads. This study held multi-level cyclic normal loading tests on the rough surfaces of double-block ballastless track interlayers under non-coincident contact conditions. The evolution of deformation and stiffness in the normal direction with cycles was examined. Based on AE signals, the damage mechanism and evolution characteristics were analyzed, and the relationship between damage evolution and roughness was discussed. The results indicate significant residual deformation and reduced normal stiffness during the first cycle of each load level, marking the main stage of deformation and damage. Deformation and damage in non-coincident states primarily originate from interlayer asperities and the matrix, and the cracking of matrix causes a sudden rise in normal displacement and a sudden drop in normal stiffness. The damage factor increases gradually with time, and the sudden peak value occurs during large asperity crushing and matrix cracking. Rougher surfaces experience an earlier onset of matrix cracking, leading to more severe damage and a larger number of cracks before complete failure. AE spectrum analysis indicates that matrix cracking results from the gradual development of large cracks. This research aims to support the long-term performance of double-block ballastless tracks.