【作者】 吴志勇；

【导师】 张肖宁；

【作者基本信息】 华南理工大学 ， 道路与铁道工程， 2014， 博士

【摘要】 疲劳损伤破坏是沥青路面的主要破坏形式之一，也是沥青路面结构设计重点考虑的问题。而沥青混合料作为沥青路面主要的建筑材料，研究其在交通荷载作用下的疲劳损伤累积进程以及疲劳寿命预测是研究沥青路面疲劳损伤破坏的重要手段和需要解决的关键性问题之一。论文依托国家自然科学基金重点项目“沥青路面随机疲劳累积损伤机理研究（51038004）”，通过不同加载方式下四点弯曲小梁疲劳试验，揭示了沥青混合料各性能指标参数的变化规律，开展了基于劲度模量衰减的与加载历史及次序相关的沥青混合料非线性疲劳损伤研究，对于改善现有的沥青路面结构疲劳设计具有重要的科学参考价值。通过4种应变水平下的单级荷载加载的四点弯曲小梁疲劳试验，提出了确定初始劲度模量以及失效判据的方法，据此给出了单级荷载作用下与劲度模量和应变大小相关的沥青混合料疲劳寿命预测方程，同时分析不同应变水平下弯拉劲度模量的衰减规律，建立了与加载次数，加载大小及劲度模量相关的幂函数疲劳累积损伤模型，确定沥青混合料疲劳损伤演变呈非线性的特性。通过不同加载方式的多级等幅荷载下的疲劳试验，获得了不同荷载大小、不同加载次数及不同加载顺序下弯拉劲度模量、耗散能变化率等疲劳损伤相关指标的衰变规律。运用以往的疲劳损伤累积模型不能准确拟合多级荷载下沥青混合料的疲劳累积损伤，预测的疲劳寿命与试验结果相差大，在此基础上提出并建立了与加载历史，加载次序相关的疲劳寿命预测方程，其预测结果比以往的疲劳寿命预测模型更准确，引入加载历史和加载次序作为疲劳损伤参数更具有优越性。采用数字散斑相关（DSCM）测量系统，基于Matlab平台结合分形理论数值计算方法自行编程，对多级荷载作用下沥青混合料疲劳损伤累积的宏观体现-裂缝的发展规律进行研究，揭示了荷载转换时疲劳损伤累积途径的变化；同时通过改变低-高应变水平加载次数的比例，确定沥青混合料在低-高加载模式下存在“锻炼效应”，通过以上研究对多级等幅荷载变换时疲劳损伤出现延迟现象给出了合理的解释。深入分析了多级荷载作用下沥青混合料的疲劳损伤累积规律，并对基于疲劳累积损伤的沥青混合料破坏进行了研究，结果表明加载历史与加载顺序对沥青混合料疲劳破坏的影响较大；在此基础上，尝试建立了一种能反映损伤现状以及加载历史、加载次序相关的基于非线性疲劳损伤累积的沥青层破坏评价的新体系，实例分析表明，它比现有的基于Miner线性准则建立的疲劳破坏评价体系更能反映路面沥青层的实际情况。本文研究所取得的成果有助于人们进一步认识沥青路面在荷载作用下的疲劳损伤累积规律，为以沥青层层底拉应变作为控制指标的沥青层破坏体系的建立奠定基础，对于完善沥青路面疲劳设计方法，提高沥青层的耐久性设计水平具有重要意义。更多还原

【Abstract】 Fatigue damage which is one of the (destructive forms)of the asphalt pavent is also animportant issue to consider for the design of the asphalt pavent structure. Asphalt mixture asthe main building material of asphalt pavent, studying its process of cumulative fatiguedamage and predicting the fatigue life under the traffic loading is an important way to studyasphalt pavent fatigue damage and destruction. And it is a key issue which needs to be solvedThis project is part of "the study about the random accumulated fatigue damage of asphaltpavent", which is supported by the key program of national natural science foundation (GrantNo.51038004). Through four-point bending beam fatigue test under different loading ways, itreveals each variation of asphalt mixture performance paraters, carries out nonlinear fatiguedamage of asphalt mixture based on the stiffness modulus decay associated with the loadinghistory and order, and has important scientific reference value for improving the existingasphalt pavent fatigue design.Through four-point bending load beam fatigue test of a single-stage load under four kinds ofstrain levels, this paper proposes a thod to determine the initial stiffness modulus and failurecriterion. According to this, this paper which gives the prediction equation of the expectedfatigue life of asphalt mix under single-stage load related to stiffness modulus and strain andalso analyzes the attenuation regulation of the flexural tensile stiffness modulus under differentstrain levels, establishes the fatigue cumulative damage model of power function which isbased on load tis, load size and stiffness modulus. By this the nonlinear characteristicalevolution of asphalt mixture fatigue damage has been determined.Through the fatigue test under the multi-level amplitude load of different loading thods, thedecay law of indicators related to fatigue damage, such as,the flexural tensile stiffness modulusand energy dissipation change rate under varying load size, different load tis and different loadorder is obtained. Previous fatigue damage accumulation model can not accurately fit thecumulative fatigue damage of the asphalt mixture under multilevel loads, so there is a bigdifference between the predicted fatigue life and experintal results. Based on these, this paperproposes and establishes a new prediction equation of the fatigue life associated with the loadhistory and load order, whose prediction results are more accurate than the prediction model ofthe fatigue life of all ti, which suggests that using load history and load sequence as fatiguedamage parater has more advantages. Using digital speckle correlation asurent system (DSCM) and the program based on theMatlab platform combined with the nurical calculate thod of the fractal theory to study thedevelopnt law of crack which is macro reflect of fatigue damage accumulation in asphaltmixture under the multi-stage loading, reveals the change of the cumulative fatigue damagepathway when load converses. At the sa ti, through changing the proportion of low and highstrain level load tis, we conclude that asphalt mixture have "training effect" under low-highload mode. According to the research above, a reasonable explanation for the delayingphenonon of the fatigue damage is got when multi-level loads convert. We deeply analyze thefatigue damage accumulation law of asphalt mixture under multi-stage loads, and study theasphalt mixture damage based on the accumulated fatigue damage. Study shows that the loadhistory and load order have a great effect on the asphalt mixture fatigue damage; we try toestablish a new evaluation system on the basis of the nonlinear accumulated fatigue damagewhich can reflect the current situation injuries, loading history and load order. Case analysisshows that it can better reflect the actual fatigue damage of asphalt pavent layer than theexisting evaluation system based on Miner linear criteria.The results of this study can help people get a better understanding of the fatigue damageaccumulation laws of asphalt pavent under loads, and lay the foundation for the establishnt ofthe controlling indicator of the asphalt layers damage system using tensile strain at the end oflayer upon layer, which has great significance for perfecting the fatigue design thod of asphaltpavent and improving the design level for the durability of asphalt layer.更多还原