沥青混合料宏细观损伤变量及非线性疲劳损伤模型研究

With the actions of environmental and traffic load repeated, damage will appear and continuously accumulate inside of asphalt pavement. And the performance of pavement materials and structure will degradation to final destruction. Choose reliable and universal damage variables describe the damage status of asphalt mixture. The internal mechanism of macroscopic damage evolution rule and modeling approach are found by physical analysis from the microscopic level. Both of the problems are the key to study fatigue damage process for asphalt mixture. .Fatigue tests are conducted under the coupled action of the load, temperature and aging of asphalt mixture. Through a CT scan for the fatigue process of asphalt mixture when a number of pre-set cycles, the idea of statistics microscopic damage mechanics is introduced. And the microscopic damage variable is defined by CT number. The macroscopic damage variable is characterized by modulus. The connection between the macroscopic phenomenological and based on analysis of probability density evolution in microscopic physics will be found. Associated macroscopic and microscopic damage variable, a nonlinear fatigue damage model of asphalt mixture will be build. The nonlinear source and microscopic damage mechanism are founded for asphalt mixture fatigue damage evolution and the damage accumulation. Not only associated macroscopic and microscopic damage variable can reflect the essence of material damage and regularity, but also simulation of the macroscopic materials and convenient for engineering application. A method for axle load conversion based on the nonlinear fatigue damage properties of asphalt mixture will be put forward. Research results will be to improve and perfect form of the principles of fatigue properties of asphalt pavement design method. The results have important theory significance and practical value.

受环境和交通荷载的反复作用，沥青路面结构内部将会出现损伤且不断演化累积，导致路面材料和结构性能的退化直至最终破坏。选择可靠、普适的损伤变量描述沥青混合料的损伤状态，从细观层次的物理分析中寻找宏观损伤演化规律的内在机制与建模途径，是制约研究并认识沥青混合料疲劳损伤过程的瓶颈。.开展荷载、温度和老化耦合作用下沥青混合料疲劳试验，不同疲劳次数下CT扫描试验，提出以CT数定义的细观损伤变量和以动模量表征的宏观损伤变量，基于概率密度演化探寻细观物理分析和宏观唯象分析之间的联系，建立关联宏细观损伤变量的沥青混合料非线性疲劳损伤模型，揭示沥青混合料疲劳损伤演化与损伤累积的非线性源及细观损伤机理。关联宏细观损伤变量既反映材料破坏的本质和规律，又能模拟材料的宏观行为且便于工程应用。提出基于非线性疲劳损伤的沥青路面轴载换算方法，研究成果将对改进和完善以疲劳特性为原则的沥青路面设计方法有重要理论意义和实用价值。

受环境和交通荷载的反复作用，沥青路面结构内部将会出现损伤且不断演化累积，导致路面材料和结构性能的退化直至最终破坏。围绕沥青混合料可靠、普适的损伤变量的选择，宏细观损伤演化规律及内在机制与建模途径等关键问题。. 结合沥青路面的力学响应及疲劳损伤现象开展了大量现场测试工作，通过现场埋设光纤光栅传感器，基于真实荷载工况开展了不同车速与轴载作用下沥青路面应变测试试验，静载应变历时曲线黏弹性明显，动载应变曲线呈现明显的压-拉-压波形。构建了路面结构层层底应变随轴载和车速变化的理论函数模型，并揭示了纵向动应变压与拉的峰值比值随车速变化的规律。. 建立了不同应力水平下沥青混合料直接拉伸疲劳动模量幂函数衰变模型，揭示了疲劳过程中沥青混合料具有非线性特性的动模量衰变规律；建立了沥青混合料剩余强度幂函数退化模型，揭示了不同应力水平下剩余强度的衰变规律；统一了基于剩余强度和刚度的损伤变量定义方法，基于刚度和剩余强度关联的损伤曲线能较好的预测沥青混合料的损伤演化规律，关联系数可认为是一材料常数；构建了重复荷载作用下基于剩余强度和动模量衰变的沥青混合料疲劳损伤演化方程。通过分区计算统计和获取各区域CT数，同时引入细观统计损伤力学的思想，以基于CT数定义的损伤变量。由于试件中部空隙率比较大，剪切破坏越严重，随之损伤变量也相对两端更大。SPT试验试件中部出现明显鼓起，验证了损伤主要出现在试件中部；揭示了沥青混合料疲劳损伤演化与损伤累积的非线性源及细观损伤机理。建立了能同时考虑加载历史与损伤演化历史影响的沥青路面轴载换算新方法，提出了超载车辆对路面破坏作用的定量分析方法，该方法能客观地评价交通荷载对路面的累积破坏作用。