【作者】 刘宇；

【导师】 张肖宁；

【作者基本信息】 哈尔滨工业大学 ， 道路与铁道工程， 2009， 博士

【摘要】 近年来,我国公路建设迅速发展,高速公路总里程已跃居世界第二位,公路建设的快速发展和公路网建设的完善极大地推动了国民经济的发展。随着经济的高速发展和交通量的日益增加,对道路建设也提出了越来越高的技术要求,除了要求解决现有道路中存在的早期损害等问题外,也提出了诸如长寿命路面等新的设计思想来提高道路使用的经济效益和社会效益。设计的目标需要由施工来实现,沥青混凝土路面施工质量管理是高速公路建设领域内最为重要的技术问题之一。目前,沥青混凝土路面在质量管理等方面仍存在着显见不足,对已建成沥青路面质量检验远不能满足对于设计的符合性检验的要求,路面芯样是对于已建成路面最好的检验手段,因此研究以路面芯样为试验标本的半圆弯曲试验具有重要的意义。半圆弯曲试验可以进行多种目的试验,在国外被称为Semi-Circular Bending Test,简称SCB试验。本文开发和应用半圆弯曲试验对沥青混合料与路面质量评价相关的性能进行研究,可以为已建成路面质量对设计的符合性检验提供一个可行的应用技术手段。本文首先采用有限元技术分析半圆试件在荷载下的应力响应和位移响应,分别建立了直径100mm和150mm半圆试件在不同支点间距下的应力系数方程和位移系数方程。在力学分析的基础上确定了合理的试验参数,并分析了半圆试件允许切割损耗值及误差值,由此确定了试件切割工艺,在考虑试件存在切割损耗的基础上提出了更为精确的应力系数。采用两种沥青混合料在四个温度下进行半圆弯曲试验和间接拉伸试验进行对比,试验结果表明半圆弯曲试验更适用于评价沥青混合料的抗拉性能;沥青混合料半圆弯曲强度在各温度下均大于间接拉伸强度,两者具有一定相关性,其转换关系与温度相关。研究开发了半圆弯曲动态模量测试方法,通过三维有限元力学分析确定了试验参数。采用开发的半圆弯曲动态模量测试方法测定了四种沥青混合料在不同温度和不同频率下的动态模量和相位角,测量结果的有限元反算表明测试方法有很好的准确性,对试验数据的变异系数分析表明试验方法具有很好的稳定性。通过时温等效原理得到沥青混合料动态模量主曲线,采用西格摩德模型拟合动态模量主曲线得到了极好的拟合效果。基于同一批试件,将多种测试方法的动态模量进行对比分析,试验结果表明半圆弯曲动态模量与四点弯曲动态模量有很好的一致性,略大于间接拉伸动态模量,小于单轴压缩动态模量,剪切动态模量远小于其他测试方法的动态模量。通过对动态模量主曲线西格摩德模型参数的对比分析,建立了不同测试方法动态模量的转换方程,转化方程具有更好的适用性和更宽的频率适用范围。基于平面应变假设,建立了半圆试件应力强度因子随裂纹深度变化的拟合方程。采用半圆弯曲试验方法对三种级配应力吸收层沥青混合料进行抗裂性能评价,试验结果表明断级配设计的应力吸收层具有更好的抗裂性能。对路面常用的四种沥青混合料进行不同温度下的抗裂性能评价,试验结果证明沥青混合料的J积分断裂韧度随温度的降低而下降,半圆弯曲试验的J积分断裂韧度试验方法可以有效的评论沥青混合料的抗裂性能,JIC对沥青混合料的抗裂性能是一个敏感的指标。JIC和KIC的对比分析表明,在较低温度下KIC可以作为沥青混合料的断裂判据,但不宜作为抗裂性能的评价指标,而JIC则是评价抗裂性能的合适指标。本文根据半经验半理论方法提出了半圆试件单试件断裂韧度预测公式。基于半圆弯曲试验,建立了疲劳断裂试验方法,采用图像技术获得了疲劳寿命N与裂纹长度a之间的关系。在考虑整体裂纹扩展的基础上,提出了采用二阶指数增长函数拟合N-a曲线的方法,得到的裂纹扩展速率有较小的离散性。采用不同频率和应力比对沥青混合料进行疲劳断裂试验,结果表明荷载频率和应力比对沥青混合料裂纹扩展速率有明显影响,这种影响在较高温度时大于较低温度。对路面常用的三种级配沥青混合料进行疲劳断裂试验,获得了沥青混合料在15℃和0℃的疲劳断裂参数,试验结果表明Paris公式中参数A随温度的降低而减小,参数n随着温度的降低而增大,由试验数据建立了疲劳断裂参数预测方程。基于CT技术得到的沥青混合料内部构造表明具有较大空隙的试件具有较小的疲劳断裂寿命,具有较长扩展路径的沥青混合料具有较大的疲劳寿命。由能耗原理分析了沥青混合料疲劳演化规律,并通过疲劳过程的位移曲线定义了疲劳破坏点。将能量耗散的概念应用于宏观疲劳裂纹的扩展过程,分析了沥青混合料在裂纹扩展过程中的总疲劳破裂能和单次疲劳破裂能的变化规律,结果表明单次疲劳破裂能基本保持稳定,总疲劳能耗符合Miner线性假定。建立了基于断裂韧度和动态模量的疲劳能耗预测方程,并结合四点弯曲疲劳试验的耗散能分析了由能耗预测疲劳寿命的影响因素。更多还原

【Abstract】 Recent years, with the rapid development of our national highway construction, total course of freeway has already taken the second place in the world. The accelerated highway construction and improved highway network has greatly prompted the national economy. However, as highway course is increasing, various premature problems have come to the fore. Except for the defect of technical standards and regulations and over-loaded vehicles, the obvious lacking of quality management and that the inspection of the asphalt concrete pavement failed to meet the requirements of compliance examination of its design are also be considered as major causes. Pavement cores are the best inspecting method for completed pavement. Therefore, the Semi-Circular Bending (SCB) test, which is chosen as its test specimens, is of great significance. Based on the SCB test, this paper has discussed dynamic modulus, fracture toughness and fatigue fracture performance of asphalt concrete, giving an analysis on the evolution rules of asphalt concrete fatigue process from the view of energy consumption.First of all, the paper analyzes a load response of semicircular specimens with two-dimensional finite element method, giving a stress coefficient fitted equation and a displacement coefficient fitted equation of two specimens, the diameters of which are 150mm and 100mm, in different distance of fulcrums. According to the specimens sizes in this research, stress and displacement response of the specimens under load is analyzed with three-dimensional finite element method to get the results of stress distribution and displacement coefficient in the tensile zone at the bottom of the specimens, which lay the theoretical analysis foundation for this research to carry mechanical tests out. Meanwhile, the causes for different researchers giving different stress coefficients are also explained here. There is also a contrastive analysis between semi-circular flexural-tensile strength and indirect tensile strength for asphalt mixture at different temperature. As a result, the former obviously exceeds the latter, while the latter is more sensitive to the temperature, i.e., the transformational relation between the two is relevant to the temperature.Based on three-dimensional finite element analysis results in the semi-circular bending test, we have developed a measuring method of the semi-circular bending dynamic modulus, with which we have measured the bending dynamic modulus and the phase angle of different asphalt mixtures at different temperatures and frequencies. Besides, we also have got the asphalt mixture dynamic modulus master curve on the basis of time-temperature equivalence principle. According to the test result of the same batch of specimens, we made two contrastive analyses: semi-circular bending dynamic modulus master curve and uniaxial compression dynamic modulus master curve; indirect tensile dynamic modulus master curve and shearing dynamic modulus master curve. We found that the uniaxial one is visibly greater than the semi-circular one and the indirect one, while the semi-circular one is similar to the indirect one, and the shearing one is clearly less than the previous three ones. Based on the mathematical model from Sigmoidal, we set the transformational relation among semi-circular bending dynamic modulus and uniaxial compression dynamic modulus and shearing dynamic modulus.Based on J Integration Theory, using semi-circular specimens of different crack lengths, this paper gives a contrastive analysis on the anti-cracking ability of three different graded asphalt mixtures at the stress absorbed layer, evaluating the J integration fracture resistance, JIC, of 4 different graded asphalt mixtures at different temperatures. The test result shows that the asphalt mixture at the stress absorbed layer with skeleton structure design has better anti-cracking ability, and that JIC decreases as the temperature falls, i.e., the anti-cracking ability decreases as the temperature falls. In this paper, we get the stress intensity factor fitted equation for the crack tip of the semi-circular specimen with the method of finite element, and make a contrastive analysis on JIC and KIC. As a result, JIC makes it suitable for evaluating the anti-cracking ability of asphalt mixtures. From the test results, this paper gives a half-experience and half-theory based separate specimen JIC predictor formula of the semi-circular bending test.Moreover, in terms of fracture mechanics theory, this paper gives a design of Fatigue Cracking test. Through graphics techniques, the relation between load times (N) and crack growth length (a) was gained. In view of nonhomogeneity of the asphalt mixture and noncontimuity of its crack growth, and taking overall growth trend of the fatigue cracking into account, we put forward the method of N-a fitted curve with 2 Exponential Growth Function, and got that, in the log-log coordinate, there is an obvious situation of crack growth three-stage in the crack growth rate and the stress intensity factor amplitudeΔK, with the data of minor discreteness character. The effect of load frequency and stress ratio on asphalt mixture crack growth rate is also analyzed in this paper. According to Paris Formula, we got the crack growth rates of different common asphalt mixtures at three layers at 15℃and 0℃, and the coefficients of the fitted Paris Formula can provide reference for the pavement anti-cracking design. And also based on CT scanning technique, we got the crack tip status of the asphalt mixture, and analyzed the cause for the fatigue life differentiation of the asphalt mixture specimens.Through Fatigue Energy Consumption Principle, this paper gives an analysis on the fatigue evolution rule of asphalt mixtures. Meanwhile, according to fatigue process displacement diagram, the paper defines fatigue fail point, analyzing total fatigue cracking energy and single fatigue cracking energy during the process of asphalt mixture crack growth, setting up Fatigue Energy Consumption Predictive Equation based on fracture toughness and dynamic modulus. Integrated with the energy consumed in the four-points bending fatigue test, it also analyzes the effect factors to fatigue life based on energy consumption, and applicated the concept of energy consumption to macro-fatigue-crack-growth process.更多还原