无砟轨道复合结构细观模型与层间脱空机理研究

The interfacial void has become one of the typical damage in ballastless track which has been widely used in Chinese high speed railway. The development of the interfacial void is mainly related to the repeated train load and the fractal contact between layers. It is necessary to study the interfacial void mechanism from the mesoscopic level. Based on the commonly used CRTS II slab track and twin-block ballastless track, three typical composite structures will be made. The meso-scale structure of the composite structure material will be acquired by the digital image techniques. The 3D data of the interfacial surface can be measured using the laser scan techniques. Based on the meso-structure of the material and the meso-profile of interfacial surface, a meso-level finite element model can be established to study the interfacial debonding and interfacial void development mechanism. Meanwhile the force transfer characteristic between layers, the bearing state and dynamic performance of the composite structure will be investigated during different interfacial connection phase, such as before interfacial debonding, after interfacial debonding and with different levels of void. The composite structures will be separated through shear experiment initially, then the two separated layers will be stacked together for the fatigue test under the repeated train load and minor relative displacement. On the basis of the 3D data of the fracture surface, the fractal theory can be applied to describe the development of the interfacial void. The interfacial force transfer parameters, stress levels and dynamic response of the structure will be recorded to verify the meso-mechanical model. Through the research of the meso-mechanical simulation and model experiment, the meso-scale mechanism of interfacial void in ballastless track composite structure can be figured out, the influence of the interfacial connection condition on the structure service performance can be explored, which can provide a solid theory foundation for the prediction and evaluation of the interfacial void in ballastless track.

无砟轨道在我国高速铁路上得到了广泛应用，层间脱空已成为无砟轨道的一种典型病害。脱空的演变与列车荷载的反复作用和离缝面的分形接触状态有关，需从细观尺度研究无砟轨道的脱空机理。针对常用的CRTSⅡ型板式轨道和双块式无砟轨道制作三类复合结构，通过数字图像处理获取材料细观构成，通过激光扫描获取结构细观三维界面，建立含粗糙界面的复合结构细观有限元模型，研究层间离缝与脱空的细观力学机理，进行离缝前后以及不同脱空阶段的层间传力特性、结构受力状态与动力响应分析。通过剪切试验分离复合结构，叠合后进行微小错动条件下的疲劳试验，基于对离缝面的激光扫描数据，应用分形理论描述脱空发展形态，测试不同脱空状态下的层间传力参数、结构层应力水平与结构动态响应，验证细观模型的正确性。通过细观模拟和模型试验研究，揭示无砟轨道复合结构脱空的细观力学机理，探讨层间状态对结构服役性能的影响，为无砟轨道的脱空预测和评估奠定理论基础。

本项目针对高速铁路无砟轨道层间离缝与脱空病害，从材料的细观构成和界面的细观形态出发，结合现场调研资料，通过理论分析、模型试验与细观模拟相结合的方法，对无砟轨道层间离缝到脱空的动态演化过程和细观力学机理进行了多方位探究。理论分析方面，运用分形几何理论和逆向工程技术，实现了对无砟轨道复合结构离缝断裂面和脱空形态的描述与重构，并提出“共形率”的概念以量化层间的脱空程度。推导了列车和温度荷载耦合作用下层间承剪能力的演变公式，并对层间承剪力的来源做了定量区分。建立了层间脱空形貌特征与力学传递特性之间的对应关系，从细观层面解释了无砟轨道层间脱空演化的力学机理。模型试验方面，通过对含离缝复合结构在循环荷载作用下脱空演变的模型试验，对层间的脱空形态演化特征和层间静、动态传力特性进行了研究，探寻了荷载作用强度、频次以及层间初始粗糙形态等因素对脱空演变的影响规律，并对不同层间状态下复合结构层间传力参数和结构应力水平进行了测试。同时，借助3D激光扫描设备，实现了层间脱空形态的数字化重构，为建立含粗糙界面的复合结构细观模型奠定基础。细观模拟方面，基于复合结构层间形态的3D测量数据，分别从离散元和有限元两个角度，建立了含粗糙离缝断裂面的复合结构细观实体模型，并采用时步迭代原理和生死单元技术，模拟了列车和温度荷载反复作用下脱空发展的过程，同时，对其层间传力性能、结构受力状态和动力响应特征进行了分析，探究了脱空随荷载作用次数的演化规律和相应的服役性能变化规律。综合以上研究，本项目建立了一套基于细观构成和细观形态的复合结构层间脱空发展模拟及服役性能评价的计算方法，用以揭示无砟轨道复合结构在荷载反复作用下脱空发展的细观力学机理和演化规律，为无砟轨道的层间脱空状态的预测和评估奠定了理论基础，为大规模高速铁路无砟轨道的安全服役提供了理论保障。