高铁桥梁无砟轨道层间连接区疲劳劣化机理分析及试验验证

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.

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。

高铁无砟轨道的层间连接区域是轨道板薄弱环节，在列车-环境长期共同作用下，损伤裂纹将率先发生于界面处，并以此为起点沿界面扩展，造成层间连接破坏；而不同类型轨道板因结构设计与受力的差异，表现出了不同的劣化特征。开展了极端气候条件对高铁无砟轨道结构性能影响研究，得到了高铁无砟轨道温度场模式，明确了温度影响的重要性，提出了通过掺入纳米材料改善CA 砂浆温度敏感性的方案。开展了高铁无砟轨道板层间界面力学性能研究及试验，探明了连接区破坏模式以剪切断裂为主，且应力水平是影响疲劳寿命的主导因素。基于粘聚区理论建立了层间连接区劣化本构关系，确定了循环荷载作用下界面起裂及裂纹扩展准则，通过DIC技术获得了粘聚强度、界面刚度、临界断裂能等关键参数。针对无砟轨道板结构层间非完美粘结特性，建立了层间可双向滑移的层合薄板和中厚板力学分析的微分形式及积分形式方程；构造了相应的层合薄板矩形单元，结合劣化本构模型，实现了高铁无砟轨道结构在温度荷载、列车荷载等作用下的静动力响应、界面损伤影响及边缘脱粘演化过程的多尺度模拟分析等。本研究为高铁无砟轨道结构体系优化、设计分析方法改进、关键材料改性及维修养护方案制定等提供了理论支撑。