粗-中-细集料配比设计与空隙率等值线分析

为了使矿质混合料达到工程要求，合理搭配不同粒径的集料颗粒，分析了矿质混合料中的集料粒径分布范围，把集料颗粒划分为粗、中和细三档，建立以粗料占比为横轴、中料占比为纵轴、细料占比为斜轴的三角坐标系，提出一种基于三角坐标系的粗、中和细集料配比设计方法；以粒径比和初始粒径为指标，建立粗、中和细料的27种组合，每种组合选择36种占比，通过离散元数值仿真试验，计算了972组虚拟试件的空隙率；构建了不同粒径比的空隙率等值曲线图，研究了粗、中、细集料组合及其占比对空隙率的影响规律。分析结果表明:初始粒径对空隙率的影响较小；粒径比对空隙率影响很大，随着粒径比增大空隙率逐渐减小；空隙率等值线具有明显的规律，随着粒径比的增大，等值线越来越密，区域性规律也越来越显著；初始粒径和粒径比作为混合料配比的2种指标，对空隙率影响程度不同，后者可作为主要指标；粗、中和细料的体积占比对空隙率的影响在三角坐标系中呈等值线变化，具有区域特征，在三角坐标系的三个顶点附近空隙率出现最大值，横轴中点附近空隙率出现最小值，且斜轴两侧空隙率具有明显差异，最大约为2.8%，斜轴以下空隙率相对较小；空隙率等值线的凸点指向纵轴顶点，凹口指向横轴中部，且等值线疏密程度可以表征空隙率差异程度。 

Design of coarse-medium-fine aggregates proportion and analysis of air void contour curves

In order to make the mineral mixture meet the engineering requirements and reasonably match the aggregate particles with different particle sizes, the distribution range of aggregate particle sizes in the mineral mixture was analyzed. The aggregates were divided into three grades: coarse, medium and fine aggregates, and a triangular coordinate system with coarse aggregate proportion as horizontal axis, medium aggregate proportion as vertical axis and fine aggregate proportion as oblique axis was established. A design method of coarse, medium and fine aggregate ratios based on the triangular coordinate system was proposed. With the particle size ratio and initial particle size as indexes, a total of 27 combinations of coarse, medium and fine aggregates were built and each combination had 36 mixing proportions. Through the discrete element simulation, the air void ratios of 972 virtual samples were calculated and the results were plotted in contour maps. The influences of coarse, medium and fine aggregates combinations and mixing proportions on the mixture air voids were studied. Analysis results show that the initial particle size has negligible impact on the air void ratio. The particle size ratio has a great influence on the air void ratio, and gradually decreases with the increase of the particle size ratio. The air void ratio contours show obvious trend. The contours become denser and the regional rules become more and more obvious with the increase of the particle size ratio. The initial particle size and particle size ratio are two types of indexes for the mixture proportion, which have different effects on the void ratio, and the latter can be used as the main index. The influences of volume proportions of coarse, medium and fine aggregates on the void ratio show contour change with regional characteristics in the triangular coordinate system. The maximum void ratio appears near the apexes of the coordinate, and the minimum void ratio appears near the midpoint of the lateral axis. The void ratios on both sides against the oblique axis are significantly different, with a maximum of about 2.8%. The void ratio below the oblique axis is relatively small. The convex points of the void ratio contours point to the apexes of the vertical axis, the concaves point to the middle of the lateral axis, and the density of the curves indicates the difference degree of the void ratios.