疲劳和冻融协同作用下水泥乳化沥青砂浆的损伤失效机理分析

The degradation of cement emulsified asphalt mortar (CAM) cushion of ballastless track slab in high-speed lines is found when subjected to the environmental and loading actions, which leads to the reduction of safety and comfort of high-speed lines. The objective of this project is to explore the performance of CAM subjected to the synergetic effects of fatigue and freezing-thawing cycles based on the in-situ conditions of high speed lines in cold regions. By means of the macro and micro experimental program, the degradation of mechanical properties of CAM under fatigue and freezing-thawing cycles is determined, and the pore characteristics, the cracking and micro structure of hardened CAM during the process of fatigue and freezing-thawing damage are observed. Thus the synergetic damage of CAM by fatigue and freezing-thawing cycles is analyzed and the key factors to influence the performance of CAM under single and multiple actions are investigated. According to experimental results, the relationship between the macro and micro behaviour of CA mortar is established, and the mechanism of fatigue and freezing-thawing cycles on the mechanical properties of CAM is revealed. Finally, a damage coefficient to describe the damage of CAM after fatigue and freezing-thawing is proposed, and a reasonable constitutive model is developed to describe the degradation of CAM. It is expected that the current research will be helpful to provide an accurate prediction of the damage development of CAM in real practice, and served as the groundwork to ensure the safety of non-ballast slab track of high-speed lines.

在环境因素和荷载因素的多重作用下，高速铁路无砟轨道水泥乳化沥青砂浆(CA砂浆)垫层性能随着服役时间增长发生劣化，严重影响了高速铁路的安全性和行车舒适性。本项目基于寒冷地区的实际情况，致力于研究CA砂浆在疲劳荷载和冻融循环协同作用下的性能演变过程。从CA砂浆的宏微观试验入手，确定CA砂浆在疲劳和冻融作用下宏观力学性能衰减规律，观测CA砂浆在劣化过程中的孔结构特征、裂缝分布和扩展情况以及硬化浆体的微观形貌，分析CA砂浆在疲劳和冻融协同作用下的复合损伤效应，探究在单因素和多因素作用下CA砂浆劣化性能的影响因素和关键影响区间。结合宏微观试验结果，建立CA砂浆宏微观行为的联系，揭示CA砂浆性能的劣化机理。提出CA砂浆受疲劳荷载和冻融循环作用后的损伤因子，建立合理描述CA砂浆劣化性能的本构模型。本项目有助于准确预测CA砂浆在实际环境下的损伤失效过程，为进一步保证高速铁路无砟轨道的安全性提供了科学依据。

本项目以高速铁路实际运营环境为背景，深入研究了在疲劳作用和冻融循环作用下无砟轨道板垫层材料水泥沥青砂浆的性能劣化趋势，对比了单一劣化因素和协同劣化因素对水泥沥青砂浆性能的影响规律，从而确定了不同劣化环境下影响水泥沥青砂浆性能的关键因素，建立了水泥沥青砂浆的预测模型。在此基础上，采用纳米材料实现了改善水泥沥青砂浆性能的方法。从研究中发现了一下主要结论：. (1)在疲劳荷载和冻融循环的协同作用下，水泥沥青砂浆的残余性能比单一疲劳荷载和单一冻融循环作用下的残余性能更小，其减小的程度和疲劳应力水平相关。当疲劳应力水平小于0.5时，冻融后水泥沥青砂浆残余性能变化较小；当疲劳应力大于0.5时，冻融后残余性能下降幅度明显，损伤程度较大。同时，先疲劳后冻融的水泥沥青砂浆的损伤程度较小。. (2)基于水泥沥青砂浆微观性能试验结果，可以推断，疲劳破坏主要以扩大水泥沥青砂浆本身基体为裂缝为主，冻融破坏则以增大水泥沥青砂浆内部孔隙为主。协同作用并不能改变其对应的破坏机理。. (3)在水泥沥青砂浆的本构模型中可以分别引入疲劳荷载和冻融破坏引起的损伤因子，通过拟合疲劳荷载和冻融循环作用后的峰值应力和应变与损伤因子的关系，建立水泥沥青砂浆受损后的应力-应变关系。. (4)添加纳米材料可以有效地提升水泥沥青砂浆的力学性能和疲劳寿命，改善水泥沥青砂浆的温度敏感性。.