基于图像分析的粗集料形状特征参数及分布规律

Shape Feature Parameters and Distribution Rule of Coarse Aggregate Based on Image Analysis

沥青混合料的路用性能受粗集料的形状特征影响显著。为解决集料基本轮廓形状特征的测量和表征问题,通过对集料进行清洗、染色、烘干、平铺拍照等一系列试验,使用MATLAB软件编程计算,对试验采集的玄武岩粒径分别为4.75,9.5,13.2,16,19 mm的粗集料图像进行了增强、分割等处理。基于数字图像处理技术计算得到不同粒径集料的大小指标(长短轴、周长和面积)。引入形状参数指标(矩形度、形状指数和棱角性),通过集料大小指标计算了不同颗粒的形状特征参数。基于统计学方法研究了各形状特征参数的分布规律,利用线性回归模型分析了各形状特征参数与级配的相关性,并通过形状参数对集料加工和混合料级配进行了评价。结果表明:矩形度在数值上体现出较好的一致性,平均值与最大值变化幅度小,粒径为9.5 mm的集料矩形度分布更均匀;形状指数的平均值和最小值变化不明显,在数值上其差异性较大;不同粒径集料的棱角性差异性较大,棱角性大于1.20的集料颗粒较少;矩形度和棱角性与集料级配之间有着较好的相关性,而形状指数与级配不相关;矩形度和棱角性能够表征混合料级配的粗细;形状指数可以评价集料加工是否符合要求,为混合料级配范围的确定提供依据。

The shape characteristics of coarse aggregate have an important influence on the road performance of asphalt mixture.In order to solve the problem of measuring and describing the basic contour shape characteristics of aggregate,after conducting a series of tests on the aggregate,such as cleaning,dyeing,drying and taking photos by tiling,the basalt coarse aggregate image which has particle size of 4.75,9.5,13.2,16,19 mm is to enhanced and segmented respectively using MATLAB software.The size indicators(long axis and short axis,perimeter and area)of different particle sized aggregates are calculated based on digital image processing technology.The shape parameter indicators(rectangularity,shape index and angularity)of different particles are introduced and calculated by the aggregate size indicator.Based on the statistical method,the distributions of shape characteristics parameters are analyzed,the correlation between each parameter and gradation is analyzed by linear regression model,and the aggregate processing and the gradation of the mixture are evaluated by the shape parameters.The result shows that(1)the rectangularity shows a good consistency in numerical value,the variation ranges of the average value and the maximum value are small,and the rectangularity distribution of the aggregate with particle diameter of 9.5 mm is more uniform;(2)the average and minimum values of the shape indicator are not significantly changed,while the difference in values is large;(3)the angularity difference of aggregates with different particle sizes is larger,and the aggregate particles with angularity greater than 1.20 are less;(4)there is a good correlation between rectangularity/angularity and aggregate gradation,while the shape index is not related to the gradation;(5)rectangularity and angularity can represent the thickness of mixture gradation;(6)shape index can be used to evaluate whether the aggregate processing meets the requirements,which can provide a basis for determining the gradation range of the mixture.