多尺度下沥青路面高温变形与裂纹协同发展机理研究及仿真分析

It is shown in field that the failure mechanism of asphalt pavements at high temperatures is quite complex. Permanent deformation and cracking occur simultaneously. The synergetic development needs to be further studied. In this study, the stress and temperature fields in asphalt pavements are coupledly simulated in laboratory tests. A permanent deformation test with full-depth asphalt layers based on in-situ conditions of pavements is developed. The specimen size, loading head size, loading pattern and temperature gradient used in the test are determined according to actual stress state, axle load spectrum and temperature field in pavements using laboratory heating test and finite element method. After performing this test, the evolution of mesostructure for asphalt pavement in the process of deformation is analyzed using CT scanning and digital image process techniques. In combination of macroscopic damage and mesostructure, the synergetic development behavior of deformation and cracking in asphalt pavements at high temperatures is studied. The composition and distribution of densification, shear flow and cracking are determined. The failure mechanism and contribution to deformation for different asphalt layers are also discovered. The nonlinear visco-elastic-plastic damage model is developed for asphalt pavements based on finite element method and multiscale modeling technique. The synergetic development behavior of deformation and cracking at high temperatures under dynamic loads is simulated numerically for asphalt pavements to understand the mechanism of high temperature distresses and to guide the anti-rutting design of structure and materials.

工程实践中发现在高温条件下沥青路面的破坏机理十分复杂，永久变形与裂纹往往会共生且相互影响，目前对两者的协同发展行为缺乏研究。本课题根据路面结构的实际应力状态、轴载谱以及温度场，结合室内保温试验和有限元方法，在室内试验中对沥青路面应力场和温度场进行耦合模拟，建立基于沥青路面实际工作状态的整体结构高温变形试验方法。进行室内试验，采用X射线断层扫描（CT）和数字图像处理技术对高温变形过程中沥青路面细观结构演变行为进行分析。通过宏观破坏和细观结构结合分析，研究沥青路面高温变形与裂纹协同发展机理，确定压密变形、剪切流动变形以及裂纹的组成与分布特征，揭示不同沥青层位的主要破坏机理和变形贡献率。基于有限元方法和多尺度关联技术，建立非线性粘弹塑性损伤模型，对动载作用下沥青路面高温变形与裂纹协同发展行为进行数值模拟，为深刻地认知沥青路面高温病害以及进行抗车辙路面结构和材料组合设计提供理论依据。

工程实践中发现在高温条件下沥青路面的破坏机理十分复杂，永久变形与裂纹往往会共生且相互协同发展，各沥青层永久变形发展规律、组成与分布特征也存在较大的差异性。本研究采用沥青面层多层整体试件，提出整体结构高温变形模拟试验，实现对沥青路面应力场和温度场的耦合模拟；采用整体结构高温变形模拟试验方法分别评价不同类型路面结构高温变形发展和分布规律及其主要影响因素；采用Computed Tomography（CT）扫描和数字图像处理技术对试验前后沥青路面结构内空隙、颗粒及裂纹的特征及分布规律等进行追踪分析，确定其细观结构演变过程；结合宏观的整体结构高温变形模拟试验和细观的CT扫描试验对不同类型沥青路面的高温变形和裂纹协调发展机理及变形组成特征进行了多尺度分析；结合CT扫描图像和有限元方法建立沥青路面高温变形虚拟试验方法，对沥青路面高温变形与裂纹协同发展行为进行了数值模拟。研究表明，整体结构高温变形模拟试验可以准确地评价不同沥青路面结构的高温性能；流变次数指数FN Index与室内试验和现场检测结果具有最好的相关性；试件加载区域空隙率变化幅度大于非加载区域；铣刨加铺路面结构中面层出现轻微的剪胀现象，空隙率增大，空隙数量减少，有裂纹形成；高温条件下不同路面结构抗车辙性能评价指标和裂纹评价指标之间一定的相关性；铣刨加铺和新建路面结构各沥青层在高温条件下表现出不同的破坏机理；高温变形虚拟试验可以准确地评价沥青路面结构的高温变形和裂缝协同发展状况。