This paper numerically investigates deformation behavior of coarse-grained granular materials with emphasis on the effect of grain size distribution (GSD). Biaxial compression tests are simulated in two dimensions using distinct element method (DEM) on a set of samples composed of uncrushable spheres following a wide variety of GSDs. The results prove that high-order characteristics of gradation, such as the shape of the GSD curve, significantly affect deformation behavior of widely-graded materials. Two grading indices are proposed to consider the combined effects of the spread and the shape of the GSD curve, and they are highly correlated with the parameters of the materials’ internal fabric. Strong correlations are found between the proposed grading indices and deformation parameters, such as those of the normal compression line and the critical state line (CSL) in the e-p space, and the deformation modulus. In contrast, using the more conventional coefficient of uniformity cannot reach effective gradation-dependent relations for those deformation parameters due to the deficiency in characterizing high-order features of gradation. This study suggests the need for incorporating high-order characteristics of gradation into a refined measure of size polydispersity in order to establish gradation-dependent relations of deformation parameters widely effective for polydisperse granular materials.

中文翻译：

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致密颗粒材料级配与变形行为的关系：高阶级配特征的作用

本文数值研究了粗粒颗粒材料的变形行为，重点是粒度分布（GSD）的影响。双轴压缩测试使用不同元素方法 (DEM) 在一组样品上进行二维模拟，这些样品由遵循各种 GSD 的不可破碎球体组成。结果证明，级配的高阶特征，如 GSD 曲线的形状，显着影响宽级配材料的变形行为。提出了两个分级指标来考虑散布和GSD曲线形状的综合影响，它们与材料内部织物的参数高度相关。在提出的分级指数和变形参数之间发现了很强的相关性，e - p空间，以及变形模量。相比之下，由于在表征层次的高阶特征方面存在缺陷，使用更传统的均匀系数无法为那些变形参数达到有效的层次依赖关系。该研究表明，需要将级配的高阶特征纳入尺寸多分散性的精细测量中，以便建立对多分散颗粒材料广泛有效的变形参数的级配相关关系。