高速铁路沥青道床材料的破坏模式与特征参数

The materials of trackbeds directly influence the operation safety, ride comfort and service life of high-speed railways. The well-graded asphalt concrete trackbeds applied in high-speed rails perform well in low permeability, noise reduction and vibration control as well as sufficient strength and appropriate flexibility. However, the risk on damage deterioration and even fracture or failure exists in the asphalt bearing layer when subjected to the high-speed wheel-rail loads. In this project, according to the theories of material damage and fracture mechanics, the failure modes and characteristic parameters were taken as the research contents around the key issue that the loading conditions and the boundary constraints of subtrack asphalt layer influence the mechanism of action for damage propagation of trackbed materials. In which, using the theoretical analysis, the visco-elastic finite element method (FEM) and the laboratory tests including bending fracture test and uniaxial compression test as well as the field tests data related to existing trackbeds, the conventional asphalt trackbed and the ballastless asphalt trackbed with appropriate asphalt layer were selected respectively as the research structures, and the fatigue cracking principle of asphalt mix was introduced to analyze the damage evolution, deterioration mechanism and failure behavior of asphalt trackbed materials. From which, the failure judgment criteria and the key mechanical indices for asphalt layer of trackbeds were defined under the circumstance of dynamic wheel-train loads, and the failure parameters and evaluation system of railway asphalt concrete in trackbeds were constructed. The research results could be taken as the theoretical support for the structural design and engineering application for asphalt trackbed in high-speed rails.

道床材料直接影响高速铁路的运营安全、行车舒适与服务寿命。密级配沥青混凝土用于高速铁路道床支承层具有防水、减振、降噪、适应路基变形、易于维护且环保可回收等优势，但沥青层材料在轮轨荷载作用下存在损伤、劣化甚至破坏之风险。项目基于材料损伤与断裂力学理论，以沥青道床破坏模式与特征参数为内容，围绕解决道床沥青层受力状态与边界约束影响道床材料损伤演化作用机制的关键问题，采用理论分析、粘弹性有限元数值计算、室内沥青混凝土试件弯曲与单轴压缩破坏试验，结合相关实测资料，合理选取高速铁路沥青有砟和沥青无砟典型道床形式，并引入沥青混合料疲劳开裂机制，开展道床沥青混凝土材料的损伤演变、劣化机理及破坏行为研究，提出沥青道床材料的关键力学指标和破坏判定准则，揭示高速铁路道床沥青混凝土材料的破坏模式，构建沥青道床材料的破坏特征参数评价体系。研究成果可为我国高速铁路全断面沥青混凝土支承层的结构设计与工程应用提供理论指导。

铁路道床是轨下基础重要的组成部分，位于轨道结构与路基面之间，直接承受、传递并分散由钢轨传下的列车动荷载。道床性能直接影响高速铁路的运营安全、行车舒适与服务寿命。由于无砟轨道具有优良稳定性和少维修性，相对于散粒体的道砟道床，我国高速铁路广泛采用水泥混凝土无砟轨道。然而，水泥混凝土无砟轨道结构在实际应用中存在刚度大、振动强、噪声高、易开裂且修复极其困难等问题。.粗粒式密实性沥青混凝土兼具强度与柔性及优良的防水性能，国外许多国家已将其用于高速铁路道床中，而我国仅开展了少量以路基面防水为目的的试验性施工和初步的理论分析，处于初期研究阶段。全断面沥青轨下基础层相对于路基面防水沥青层具有明显的结构差异性，即前者除了防水功能要求外，还需要承担轨道传递下来的列车荷载。列车动荷载作用于沥青层上，沥青混凝土材料内部产生疲劳损伤积累。当损伤变形超过一定的限值，道床沥青层将产生破坏，进而引起轨道不平顺并危及行车安全。因此，明确高速铁路道床沥青混凝土材料的破坏模式与特征参数，是沥青道床结构能实际应用和推广的关键。.本项目采用动力有限元分析方法，优选沥青道床结构型式；针对最优结构组合，描述相应沥青层在不同列车动荷载作用下的受力状态；通过数值计算和室内试验相结合的手段，分析了高速铁路道床沥青层的破坏行为；提出了列车动载环境中道床沥青层的破坏判定准则和关键力学指标，构建了高速铁路沥青道床材料的特征参数评价体系。研究成果可为高速铁路全断面沥青道床的进一步研究和相关应用提供理论依据。