【作者】 刘宏富；

【导师】 郑健龙；

【作者基本信息】 长沙理工大学 ， 道路与铁道工程， 2012， 博士

【摘要】 沥青路面是我国目前主要采用的路面结构类型，沥青混合料作为沥青路面的主要建筑材料，其疲劳性能直接影响路面的使用性能和使用寿命。同时，沥青混合料作为一种粘弹性材料，沥青混合料的力学性能与荷载作用时间、试验温度等有关。论文依托国家自然科学基金重点项目“沥青路面结构设计的若干基础理论问题研究”，针对沥青混合料的材料特点，通过直接拉伸疲劳试验和不同疲劳次数后的剩余强度试验，揭示其刚度和强度衰变规律，开展基于刚度和强度衰变的沥青混合料非线性疲劳损伤研究，对于改进和完善现行沥青路面结构设计具有重要理论意义和实用价值。通过速度特性试验发现加载速率对沥青混合料强度影响显著，强度随加载速率增大而呈幂函数趋势增长；在5种应力水平下进行了直接拉伸疲劳试验，引入动载强度和真实应力比的概念，建立了基于真实应力比的疲劳方程，该方程既可以体现重复加载的疲劳破坏，又可以涵盖一次加载的强度破坏；应用真实应力比疲劳方程，提出了一种沥青面层抗拉强度结构系数计算新方法。通过分析不同应力水平下直接拉伸疲劳的动模量衰变规律，建立了动模量幂函数衰变模型，动模量衰变具有确定的非线性特性，应力水平越大动模量随寿命比衰变的越快；提出了能考虑临界损伤度的疲劳损伤修正模型，构建了基于刚度衰变的非线性疲劳损伤演化方程；通过两级荷载下的疲劳试验，验证了沥青混合料疲劳损伤累积的非线性，绘制了两级荷载加载路径图，直观而合理的解释了其试验结果。通过不同疲劳次数后疲劳剩余强度试验，建立了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；构建了与应力水平相关的基于剩余强度的沥青混合料疲劳损伤演化方程。通过对强度和刚度定义的损伤变量的比较，揭示了基于强度和刚度衰变定义损伤变量内在联系，选用组织敏感量剩余强度比组织不敏感量刚度作为疲劳损伤评价参数更具有优越性。结合剩余强度和刚度定义损伤变量时的优点，统一了基于剩余强度和刚度的损伤变量定义方法，提出了剩余强度和刚度关联的损伤变量计算修正公式。应用沥青混合料的非线性疲劳损伤演化方程，建立了一种能考虑损伤程度或加载历史影响的轴载换算新方法，改进了传统的轴载换算方法，给出了不同轴载修正系数B随年限变化的诺模图，算例分析表明传统轴载换算方法低估了累积轴载作用次数。研究成果对于推进沥青路面轴载换算方法的发展，完善沥青路面设计方法，提高沥青路面耐久性和设计水平有重要意义。更多还原

【Abstract】 The asphalt pavement is the main type of pavement structure. Asphalt mixture ofasphalt pavement construction materials, the fatigue performance directly affects theperformance and service life of the pavement. Meanwhile, the asphalt mixture as aviscoelastic material, the mechanical properties of the asphalt mixture related withloading and test temperature. This paper relies on the National Natural ScienceFoundation Key Project of“Investigation into Fundamental Issues in AsphaltPavement Structural Design". For the material characteristics of the asphalt mixture,direct tensile fatigue and the different remaining number of fatigue strength test arecarried out. The aim of this study is to understand the process of asphalt mixture infatigue damage of production, evolution and accumulation under repeated loading,and reveal the decay law of stiffness and strength of asphalt mixture in fatiguedamage. Nonlinearity fatigue damage properties of asphalt mixture based on the decayof the dynamic modulus and residual strength are investigated. Results to improve andrefine the existing asphalt pavement structural design has important theoreticalsignificance and practical value.Firstly, direct tensile strength test is carried out at different loading speed. Thetest results show that the effect of loading speed on strength of asphalt mixture issignificant, and their relationship curve can be fitted by power function. Direct tensilefatigue tests are carried out at five kinds of stress level. The fatigue equation based onreal stress ratio is established by the concept of dynamic load strength and real stressratio. This fatigue equation can not only reflect the fatigue damage under repeatedloading, but also cover the strength failure under one loading. A new calculationmethod of tensile strength structure coefficient is put forward by fatigue equationbased on real stress ratio.Secondly, the deformation and the decay law of modulus of the direct tensilefatigue are analyzed in different stress levels. A power-law decay of dynamic modulusmodel is built. The dynamic modulus decay law with nonlinear characteristics isdetermined. The dynamic modulus with the life of the faster decay, and the decayparameter m with the stress level increase by the greater the stress level. Correctionmodel to consider the critical value of fatigue damage is put porward. The nonlinearfatigue damage evolution equation based on the decay law of stiffness is established. The fatigue test is carried out under two-stage stress levels. The law of nonlinearfatigue damage cumulative of asphalt mixture is verified. And the test results areexplained intuitively and reasonably using two-stage loading route figure.Thirdly, the residual strength test of asphalt mixture is carried out in differentstress levels. Degradation of residual strength of the power function model isestablished. The decay law of the residual strength under different stress levels isrevealed. The nonlinear fatigue damage evolution equation based on the residualstrength degradation is established. Under the conditions of same material and liferatio, the damage based on residual strength is greater than the damage based onstiffness. Strength is better than stiffness as fatigue damage variable. Combined withthe advantages of the residual strength and stiffness of damage variable, a definitionof damage variable based on residual strength and stiffness is unified. A powerfunction by the damage variable Dsand Dfbased on the residual strength and stiffnessis built.Finally, based on the nonlinear fatigue damage properties of asphalt mixtures, anew asphalt pavement axle load conversion method is established with consideringthe degree of damage or loading history impact. The nomogram of axle loadcorrection factor B changes with the years is given. Through examples the impact ofthe traffic on the road is underestimated by the current axle load conversion method.Research results have important meaning for promoting the development of axleload conversion method, further perfecting the asphalt pavement design methods andimproving the durability and service level of asphalt pavement.更多还原