高速行车激励与环境侵蚀耦合致无砟轨道长期服役性能衰变机制及失效准则

The damage evolvement of slab track under the coupling effect of train load and the environment actions is challenging and needs to be solved. And the research of how the accelerated degradation of cement-based materials (such as concrete and CA mortar) leads to the long-term performance of slab track, due to mechanical and environmental factors, is the key to solve the problem..Taking the CRTS I prefabricated slab track for instance, based on the Continuum Damage Mechanics (CDM) method, the strong vibration characteristics of high-speed moving train load is investigated. Under the coupling effect of vibration fatigue load and the environmental factors, such as rain erosion, chloride ion erosion, freeze-thaw cycles etc, and a proper dissipative potential function is chosen to get the damage variable expression with regard to residual strain. Reasonable micro plastic strain equations of cement-based materials are selected to deduce the damage growth rate, thus the fatigue damage constitutive models under different service conditions can be built. The constitutive models of the cement-based materials are verified and related parameters are confirmed by performance the dynamic performance degradation tests. Combining the material constitutive models with damage variables and vehicle-track dynamics, finite element analysis of slab track structure will be carried out. The failure criterion and critical values are thus put forward. Besides, we will establish equations with regard to the load level and fatigue life under the erosion environment, to predict the residual service life.

无砟轨道在列车高频振动荷载和环境侵蚀下的损伤演化是极具科学挑战但又必须解决的问题。而研究混凝土、砂浆等水泥基材料在力学、环境因素耦合作用下的劣化加速，及加速导致宏观无砟轨道的长期服役性能降低，是解决该问题的突破口。.本项目以CRTS I型板式无砟轨道为例，从连续损伤力学的基本理论出发，依据高速行车激励的强振动特性，考虑其分别与雨水、氯离子侵蚀、冻融等环境因素的耦合作用，选定合理耗散势函数，得到关于残余应变的损伤变量表达式；选用合适的材料微塑性应变方程，推导材料的损伤发展率，建立不同服役条件下水泥基材料的疲劳损伤本构模型；利用材料动态性能衰变试验验证模型，并确定模型参数；结合含损伤变量的材料本构模型和“车辆-轨道”系统动力学，进行荷载和环境侵蚀作用下的无砟轨道结构力学有限元分析；提出构件的失效准则和失效临界值；建立能描述侵蚀环境下荷载水平与疲劳寿命关系的方程，对无砟轨道的剩余寿命进行预测。

本项目结合无砟轨道系统病害的现场调研成果，以CRTS I型板式无砟轨道为例，针对混凝土、水泥乳化沥青砂浆等水泥基材料分析了列车高频振动荷载与酸雨、氯离子侵蚀等环境因素耦合作用下的动态力学性能演化。通过轮轨作用力和钢轨支点压力的现场测试，获取了真实状态下的客车荷载作用形式；利用室内试验进行了无砟轨道水泥基材料疲劳耐久性试验、胶垫老化试验及侵蚀环境下水泥基材料性能演变试验等，获取了胶垫老化规律、水泥基材料的本构关系及力学性能演变机理。.基于有限元法建立了车辆-轨道垂向耦合动力学模型，主要研究了不同车速、不同基础刚度及不同砂浆损伤程度对轮轨力的影响，并应用统计学方法分析了轮轨力分布特征，同时结合测试数据对模型进行了验证。基于轮轨系统耦合动力学理论，建立了含损伤的车辆-轨道-路基垂向耦合振动模型，并嵌入材料疲劳损伤本构子模型，研究了砂浆离缝高度、底座板脱空长度、轨道不平顺谱等对无砟轨道结构动力响应的影响。通过建立脱空状态下CRTS I型板式无砟轨道疲劳分析实体模型，利用P-M线性疲劳累积损伤准则，对列车荷载作用下的轨道板进行了疲劳寿命预测。.通过现场调研、现场/室内试验和理论分析，本项目形成的一系列理论成果完善了我国无砟轨道设计体系，为确保无砟轨道良好服役性能和长期安全运营提供了理论依据。