基于X-ray CT图像的沥青混合料车辙过程空隙分布评估  

Assessment of Air Void Distribution of Rutted Asphalt Mixtures Using X-ray CT Technology

作　　者：张宇 王伟成 方珑 刘晋周 肖传语 于斌[3] ZHANG Yu;WANG Weicheng;FANG Long;LIU Jinzhou;XIAO Chuanyu;YU Bin(Zhangjiagang Transportation Bureau,Suzhou 215600,Jiangsu,China;China Design Group,Nanjing 210014,China;School of Transportation,Southeast University,Nanjing 210096,China)

机构地区：[1]张家港市交通运输局,江苏苏州215600 [2]华设设计集团股份有限公司,南京210014 [3]东南大学交通学院,南京210096

出　　处：《北京工业大学学报》2024年第4期508-522,共15页Journal of Beijing University of Technology

基　　金：国家自然科学基金资助项目(51878163)。

摘　　要：X射线计算机断层扫描(X-ray computed tomography,X-ray CT)技术作为一种无损测试方法,已被广泛用于评估沥青混合料中的空隙结构和与空隙有关的病害。基于X-ray CT和图像处理技术,从细观结构层面探讨了车辙变形过程中沥青混合料的空隙结构特征。提出了体积等效球棍模型来表征空隙连通性的变化,用改进的环扇分割变异系数、位置偏心率和球度分别描述了空隙的分布和形状特征。结果表明,车辙对沥青混合料空隙结构的影响机制因混合料类型而异。与密级配沥青混凝土(AC-13)相比,沥青玛蹄脂碎石混合料(SMA-13)中的空隙更加不均匀和离散,尤其是那些体积小于0.01 mm^(3)的空隙。此外,SMA-13中的空隙连通性和分布更容易受到外部荷载的影响,其粗集料在变形过程中往往会产生定向移动进而改变初始位置。尽管车辙变形同时增加了2种混合料中空隙的水平不均匀性,但AC-13的竖向不均匀性减少,而SMA-13的竖向不均匀性增加。加载使AC-13混合料的空隙几何形状变得复杂和分散,而SMA-13则相反,预示着与AC混合料相比,SMA混合料在加载1 h后仍保持抵抗车辙破坏的潜力。总体而言,沥青混合料中空隙的拓扑特征及其在车辙变形过程中的动态响应主要取决于混合料的级配形式。X-ray computed tomography(X-ray CT)technology as a non-destructive testing method has been widely used to evaluate the air void structure and void-related distresses in asphalt mixtures.In this study,air void structural features of asphalt mixtures during rutting deformation procedure was investigated at the meso-structural level based on X-ray CT and digital image processing techniques.A volume-equivalent ball-and-stick model was proposed to characterize the changes of void connectivity.The distribution and shape features of air voids were described using the variation coefficient of modified annular-sector segmentation,positional eccentricity ratio,and sphericity,respectively.Results indicate that the influencing mechanism of permanent deformation on the air void structure of asphalt mixtures varies with the type of mixtures.Air voids are more heterogeneous and discrete in stone mastic asphalt(SMA-13)mixture compared to dense-graded asphalt concrete(AC-13),particularly for those with volume less than 0.01 mm^(3).Moreover,the air void connectivity and distribution in SMA-13 is more susceptible to load as the coarse aggregates tend to shift their positions during deformation.Although the rutting deformation increases the horizontal inhomogeneity of air voids in both mixtures,it reduces the vertical inhomogeneity of AC-13 but increases that of the SMA-13.Loading complicates and disperses the void geometry of AC-13 mixture whereas the opposite is true for SMA-13,foreboding that SMA mixtures maintain the potential to resist rutting failure after one hour of loading compared to AC types.In general,the topological characteristics of air voids within asphalt mixtures and their dynamic response during permanent deformation are principally dependent on mixture gradations.

关 键 词：沥青混合料 空隙 三维分布 连通性 X射线计算机断层扫描技术 车辙变形 

分 类 号：U414[交通运输工程—道路与铁道工程]