【作者】 李静；

【导师】 戴经梁；

【作者基本信息】 长安大学 ， 道路与铁道工程， 2004， 博士

【摘要】 我国高等级公路沥青路面目前普遍存在早期破坏现象。路面病害的主要形式是以疲劳开裂及低温开裂为主的路面开裂和以车辙为主的永久变形。除了施工和材料方面的原因外,这在很大程度上说明采用弯沉作为设计指标的沥青路面设计方法已不能有效控制沥青路面的病害;此外,交通量的快速提高和超重车比例的增大等交通流/车辆组成结构的改变也在一定程度上对设计方法提出了新的要求。为此,本文在对沥青混合料的疲劳开裂、永久变形和低温开裂进行试验研究和理论分析的基础上提出了采用疲劳开裂、永久变形和低温开裂等路用性能指标来进行沥青路面设计的新思路,并对设计方法进行了探讨。 沥青混合料是一种性质复杂的工程材料,影响其性能的因素众多,单纯的理论法和经验法都不能很好地反映其性质,较为理想的途径是在以往研究的基础上选择适宜的理论,通过相应的试验研究进行补充和修正,从而得到符合实际情况的研究结果。作者在分析国内外已有成果的基础上,采用Burgers粘弹性模型作为研究沥青混合料各性能指标的基础本构模型,并根据各指标不同的特点进行了修正。据此,提出了对疲劳开裂、永久变形和低温开裂性能的室内试验研究方案;在对原始试验数据进行处理时,针对试验数据量较大的特点,作者对数据分析方法进行了专门的研究,引入了基于不等距节点的二次B样条和非线性最小二乘Levenberg-Marguardt方法对试验数据序列进行筛选以及沥青混合料本构模型的拟合,克服了现有模型参数识别方法主观性强和准确性较差的不足。同时,以试验研究和数据分析得到的Burgers模型为基础,根据各指标特点进行修正后,采用粘弹性层状体系理论对常用的沥青路面结构进行结构分析,得到各指标的性能预测模型。 本文通过对沥青混合料的粘弹性力学分析以及试验研究证实沥青混合料在疲劳过程中存在能量耗散,且耗散能的累积与沥青混合料的疲劳开裂的发生存在联系。据此,提出采用耗散能作为判断沥青混合料是否发生疲劳开裂的准则。同时,通过对沥青混合料小梁弯曲疲劳的试验研究,证实了沥青混合料的疲劳是材料内部的损伤发生、发展并最终导致宏观裂缝和断裂的过程,要准确地反映沥青混合料的疲劳特性,必须计及疲劳试验中损伤演化的影响。本文运用损伤力学方法定义了等应力幅疲劳试验中试件应变幅的变化规律作为疲劳损伤函数,通过对小梁弯曲疲劳试验过程的分析,得出与应力比、加载时间相关的损伤函数,用以对沥青混合料疲劳方程进行损伤修正。通过对劈裂动态蠕变的试验研究,运用Levenberg-Marguardt方法对试验结果进行分析,确定了Burgers更多还原

【Abstract】 Nowadays, there are many early destructive phenomena occurred in asphalt pavement of high-type highway in our country. The main destructive formals are fatigue cracking, thermal cracking and permanent deformation. Except for the results of construction and materials, this situation can be explained that the design method used deflection as design index is not able to control diseases in asphalt pavement effectively. Also, the rapid arise of traffic volume and the rate of heavy tracks challenge the current asphalt pavement design method. Thus this paper prompted new thought using fatigue cracking, permanent deformation and thermal cracking as indices to design asphalt pavement based on the theory analysis and test research, and discussed on asphalt pavement design method.Asphalt is a kind of complicate engineering materials. There are many factors that will affect it. Theory method or empirical method can not represent its character well. So selecting and modifying proper theory based on former research results will be a good idea to gain achievements reality. Based on the existing achievements, the author selected Burger’s visco-elastic model as constitute model, and modified it according to specified property of each index. After that the author put forward test scheme for fatigue cracking, permanent deformation and thermal cracking. The author performed research on data analysis method to processing mass testing data. Among this, B-spline based on unequal node was introduced to screen test data series, and Levenberg-Marguardt method of nonlinear least square method to fit asphalt constitute. Finally, the author used visco-elastic layered system program to analysis conventional asphalt pavement structure, and achieved performance evaluation model of each index.This paper proved energy dissipation existing in the process of fatigue of asphalt by the visco-elastic analysis and test research, also the accumulation of dissipation energy relating to fatigue cracking of asphalt. Thus dissipation energy was used as criterion to evaluate the fatigue cracking potential of asphalt. By the beam bending fatigue test research, asphalt fatigue was proved to be process of damage occur, develop and cracking in the asphalt cement. Thus the damage evolution should be considered in the research of asphalt fatigue. This paper defined the change of strain amplitude in the stress control fatigue test as fatigue damage function. The function could be obtained by analyzing the process of beam bending fatigue test which was stress and load time related. Then the function could be used to modify fatigueequation. The visco-elastic parameters were obtained by splitting creep test and Levenberg-Marguardt method. Thus the fatigue equation considering damage was constituted to evaluate the fatigue potential of asphalt pavement. This paper used the fatigue equation evaluating the conventional asphalt pavement successfully after analyzing the structure by visco-elastic layered system program. Finally, the design method of fatigue cracking of asphalt pavement method was discussed.The author introduced Norton rule into Burger’s model to attribute the permanent deformation of asphalt well. The visco-plastic parameters were received by uniaxial static creep test combining Levenberg-Marguardt method. Then the parameters were introduced into evaluation model based on Shell method to predicting permanent deformation. After that, the author used the modified Burger’s viscoelasticplastic model as constitute model, analyzed the conventional pavement structure by visco-elastic layered system theory, and predicted permanent deformation. Finally, the permanent deformation design method was discussed.In the research of thermal cracking performance of asphalt, energy criterion was introduced to judge whether asphalt crack or not. That is, when the energy produced by temperature dropped was larger than the energy needed by asphalt to crack, the crack would occur. Then the method to calculate asphalt cracking energy by asphalt bending test was put forward, also the method to gain the visco-elastic parameters of Burger’s model by asphalt bending creep test at low temperature accompany with Levenberg-Marguardt method. After that, the author gave the calculation formula of asphalt thermal stress based on Burger’s visco-elastic model and boundary conditions, and the method to calculating stain energy produced by thermal stress. Thus the method was established using energy creation to evaluate the crack potential of asphalt pavement. Finally, an example was gave to illustration the method.Finally, the author generalized the whole paper, gave some advice to asphalt pavement design used pavement performance of asphalt as design indices, and put forward tentative ideas to future research.更多还原