Zhao Shiwei, Zhao Jidong, Guo Ning
Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clearwater Bay, Kowloon, Hong Kong.
College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China.
Phys Rev E. 2020 Jan;101(1-1):012906. doi: 10.1103/PhysRevE.101.012906.
We examine the signatures of internal structure emerged from quasistatic shear responses of granular materials based on three-dimensional discrete element simulations. Granular assemblies consisting of spheres or nonspherical particles of different polydispersity are sheared from different initial densities and under different loading conditions (drained or undrained) steadily to reach the critical state (a state featured by constant stress and constant volume). The radial distribution function used to measure the packing structure is found to remain almost unchanged during the shearing process, regardless of the initial states or loading conditions of an assembly. Its specific form, however, varies with polydispersities in both grain size and grain shape. Set Voronoi tessellation is employed to examine the characteristics of local volume and anisotropy, and deformation. The local inverse solid fraction and anisotropy index are found following inverse Weibull and log-normal distributions, respectively, which are unique at the critical states. With further normalization, an invariant distribution for local volume and anisotropy is observed whose function can be determined by the polydispersities in both particle size and grain shape but bears no relevance to initial densities or loading conditions (or paths). An invariant Gaussian distribution is found for the local deformation for spherical packings, but no invariant distribution can be found for nonspherical packings where the distribution of normalized local volumetric strain is dependent on initial states.
我们基于三维离散元模拟，研究了颗粒材料准静态剪切响应中出现的内部结构特征。由不同多分散性的球体或非球形颗粒组成的颗粒集合体，在不同的初始密度下以及在不同的加载条件（排水或不排水）下稳定剪切至临界状态（一种以恒定应力和恒定体积为特征的状态）。用于测量堆积结构的径向分布函数在剪切过程中几乎保持不变，无论集合体的初始状态或加载条件如何。然而，其具体形式随粒度和颗粒形状的多分散性而变化。使用集合Voronoi镶嵌来研究局部体积、各向异性和变形的特征。发现局部反固体分数和各向异性指数分别遵循反威布尔分布和对数正态分布，这在临界状态下是独特的。经过进一步归一化，观察到局部体积和各向异性的不变分布，其函数可由粒度和颗粒形状的多分散性确定，但与初始密度或加载条件（或路径）无关。对于球形堆积，发现局部变形的不变高斯分布，但对于非球形堆积，未发现不变分布，其中归一化局部体积应变的分布取决于初始状态。
