无砟轨道是高速铁路主要采用的轨道类型，其在高速列车的反复作用下，易发生疲劳损伤、变形累积，造成轨道不平顺。桥上无砟轨道会因桥梁变形而承受弯曲、翘曲、局部挤压等作用，加速劣化破坏，严重影响轨道耐久及行车安全。层间连接区是无砟轨道结构劣化的源点，将粘聚区模型应用于层间连接区的开裂模拟，研究其在简单和复合循环加载条件下的起裂条件及损伤累积规律，建立单调-循环加载过程界面及材料开裂的统一本构模型，确定循环加载规则。基于增强有限元方法框架，通过位移关联及映射方式解决常规有限元网格对物理区域的依赖问题，采用Arlequin方法建立关联轨道结构宏观整体性能与界面剥离、材料开裂等细观行为的并发多尺度分析模型，实现对无砟轨道层间连接区复合循环加载条件下劣化过程模拟并揭示其疲劳退化机理。本项目相关成果可为无砟轨道结构发展及其量化维修标准制定等提供理论基础，以进一步提升高速铁路无砟轨道技术。

Ballastless tracks are widely used in high speed railway lines. Due to the fatigue damage and accumulated deformation caused by the cyclic actions of running trains, the ballastless track had a irregularity form. On the other hand, the deformation of the bridge leads to flexibility, warping and local compression in ballastless tracks, which accelerates the degradation of ballastless tracks and has a direct impact on running safety and comfort. The interfaces between contacting layers is the damage source of the ballastless track. In this proposal, the cohesive zone model (CZM) is employed to simulate the cracking behavior of the interface and materials of the interlayer. The crack initiation condition, the damage accumulation law and a unified constitutive equation of the interlayer under monotonic and cyclic loading are established. Furthermore, the loading-unloading rule is determined. Based on the framework of the augmented finite element method, the mesh-dependent issue in traditional finite element method is resolved through displacement connectivity and mapping manner. The concurrent multi-scale model, which connects the global structural behavior of track structures and interface debonding and cracking in materials, is obtained by using Arlequin method. This model is applied to simulate the damage process and to reveal the fatigue damage mechanism of the interlayer of the ballastless track under cyclic loading condition. The results in this proposal can provide a theoretical foundation for the development of track structures and the establishment of rehabilitation strategy, which is expected to improve the performance of the ballastless track.