【作者】 王聪；

【导师】 郭乃胜；

【作者基本信息】 大连海事大学 ， 道路与铁道工程， 2012， 硕士

【摘要】 沥青混合料的宏观性能与组分相材料性能和内部结构特征等密不可分,因此从微细观角度研究沥青混合料宏观性能是十分必要的。考虑微细观结构特征及其演变的力学试验的数值模拟,它将组分材料性能和宏观性能定量地结合起来,进而把握沥青混合料不同力学特性之间的平衡,并避免了大量的室内经验性试验。本文首先采用CT技术和DIP技术研究两种成型条件下三种级配沥青混合料试件的内部空隙特征,并采用数学模型对其进行表征。结果表明,沥青混合料的空隙空间分布规律受试件成型方法及级配类型的影响较大。不同级配条件下,马歇尔试件内部空隙分布沿着高度方向总体呈现对称形状,而静压试件内部空隙分布则为“一端大,一端小”的形状；相同级配条件下,静压试件的平均空隙率和平均空隙数量均较大,但平均空隙等效直径相差较小；采用两参数数学模型能够表征沥青混合料内部空隙空间分布规律,以及成型方法和集料级配对其的影响。再则,基于黏弹性理论,利用CT技术、DIP技术和FEM方法对沥青混合料二维数值模型进行虚拟间接拉伸试验和虚拟蠕变试验研究,通过分析两种试验条件下均质模型与非均质模型内部结构力学响应,提出虚拟蠕变试验最佳试验面的选取方法,并分析了劈裂荷载作用下混合料损伤开裂位置及原因。结果表明,与均质模型相比,非均质模型可以更准确地模拟蠕变实验；沿试件高度方向选择不同的试验截面不会对数值试验结果产生影响,因此沿此方向的任意截面均可作为虚拟蠕变试验的最佳试验面。非均质模型与均质模型的间接拉伸试验的应力S11与S22曲线变化趋势均相同；均质模型最大压应力位于模型中心,非均质模型最大拉应力位于砂浆与粗集料的界面处,且竖向路径的最大拉应力大于横向路径的最大拉应力,据此推断出沥青混合料损伤开裂位置主要集中于竖向路径最大拉应力处。最后,基于CT技术、DIP技术和FEM方法,利用软件Mimics对沥青混合料三维数值模型进行重构研究。并对比分析真实沥青混合料试件与数值模型内部结构中各组分在体积含量方面的差异,验证了该三维数值模型的正确性。更多还原

【Abstract】 The macroscopic performance of asphalt mixture has a close correlation with its internal structural characteristics and components behaviors. Thus, it is quite essential to study on macroscopic performance of asphalt mixture from the microscopic perspective. Numerical simulation of mechanical behaviors experiments considering microscopic structure characteristics and its evolution, which combines macroscopic performance with components of asphalt mixture quantitatively, moreover, controls the balance between different mechanical behaviors of asphalt mixture, and saves extensive experiential laboratory test.Firstly, the air voids distribution of three gradations of aggregate was characterized by using X-ray computed tomography and digital image processing technology based on the laboratory compaction methods of fabrication specimens in China. Furthermore, a mathematic model was made to present for describing the air voids distribution internal structure of asphalt mixtures by means of statistical analysis. The results showed that the gradation of aggregate and compaction methods had considerable influence on air voids distribution in the internal specimens, which was found to display symmetrical feature along the depth of Marshall specimen, whereby distribution of air voids in the static compacted specimen is nonsymmetrical along the depth, and the number of air voids on top part of a specimen was bigger than at bottom part. The number of air voids was more bigger and the fluctuations along the depth was more remarkable, the air voids size was almost consistent in static compacted specimens compared with the Marshall specimens in uniform gradation of aggregate. The statistical analysis performed validated the applicability of a two parameters mathematics model for characterizing air voids distribution of asphalt mixture, and the model could quantify the effect of compaction methods and gradation of aggregate on air voids.In addition, according to the theory of viscoelasticity, with the technique of X-ray CT, DIP and FEM, the indirect tensile test and numerical creep test were conducted to two-dimension numerical model of asphalt mixture. The selection method for the location of the optimum test section was proposed through the analysis on the internal structural mechanical response of homogeneous model and heterogeneous model, meanwhile, the location of damage cracking of asphalt mixture and its reasons under the splitting load effect was analyzed. The results showed heterogeneous model simulated creep test accurately as compared with homogeneous model. Different sections along the height direction had no impact on the results of numerical test. Therefore, any section along this direction may become the optimum test section. Variation trend of S11curve and S22curve was identical for two models mentioned above. The maximum compressive stress of homogeneous model appeared on the pivot of the model, the maximum compressive stress of heterogeneous model appeared on the interface of mortar and coarse aggregate, and the compressive stress along vertical path was bigger than the compressive stress along horizontal path, thereby the internal location of damage cracking of asphalt mixture can be concluded on the maximum compressive stress along vertical path.In the end, the reconstruction analysis on three-dimensional numerical model was performed using Mimics software based on X-ray CT, DIP and FEM. Additionally, a comparative analysis was carried out in terms of volume fraction of internal structural components of asphalt mixture specimen and numerical model, then the accuracy of three-dimensional numerical model was verified.更多还原