DEM meso-damage analysis for double-block ballastless track with non-coincident interlayer contact

Interlayer cracking has become a major defect in ballastless tracks, and the uniaxial compression behavior and damage under non-coincident interlayer contact have become a key research focus to support service performance. This study establishes a discrete element model for the non-coincident interlayer contact of composite specimens of double-block ballastless track under normal loads. The normal load–displacement curve was obtained, and the meso-damage characteristics with non-coincident interlayer contact were investigated. By analyzing the changes in force chains and crack propagation during the loading process, the damage mechanism of non-coincident interlayer contact is clarified. The influence of roughness on the damage behavior of composite specimens under non-coincident interlayer contact is also discussed. The results show that: 1) The normal displacement increases nonlinearly under normal loads, and during the loading process, the bonding between particles on the rough interface breaks, leading to a sudden drop in load; 2) there is a linear relationship between the number of cracks and displacement in the interlayer region, while in the matrix region, the relationship is stage-dependent. During the stage where damage occurs in both the interlayer interface and matrix, the matrix begins to fail, with 83% of all cracks appearing in this stage; 3) there is a correlation between the force chain and the development of damage in the specimens. When interlayer spalling occurs, shear cracks dominate; when the matrix begins to crack and penetrate, tensile cracks dominate; and 4) the peak strength of specimens with non-coincident interlayer contact and R_a follows an exponential function relationship. As roughness increases, the failure mode of the specimens shifts from primarily matrix cross-penetration to primarily interlayer material spalling. Additionally, the proportion of cracks in the interlayer region relative to the total gradually increases. The results of this study will contribute to a deeper understanding of the damage mechanism after interlayer cracking in ballastless tracks, particularly the damage evolution characteristics at the mesoscopic level.