Pore characteristics play central roles in the transport of water and gas through granular soils, which is relevant to a wide range of geotechnical and geoenvironmental applications. In this study, a numerical procedure combining the discrete element method and pore network model is presented to relate the physically representative pore structure to the particle geometric features, and rapidly predict the macroscopic flow properties of granular assemblies. This numerical procedure is applied to investigate the effects of particle gradation and geometry on the pore characteristics and water retention curves of granular soils under isotropic compression. The results indicate that a larger uniformity coefficient (C_u) of particle diameters results in a lower porosity. The porosity first decreases and then increases as the aspect ratio (AR) of the particles increases from 1.00 to 2.50 and reaches the minimum at AR = 1.75. As C_u ranges from 1.00 to 2.16, the standard deviations and mean values of pore geometry and connectivity parameters, including pore and throat diameters, pore spacings, and coordination numbers, present linear correlations. The logarithm of air entry pressure decreases linearly with the increasing logarithm of mean pore diameter in response to the variations in both C_u and AR. A higher pore diameter variance induced by a smaller C_u produces a lower fitting parameter m in the van Genuchten equation for water retention curves.

孔隙特征在通过粒状土壤的水和天然气的运输中起着核心作用，这与广泛的岩土和地质环境应用有关。在这项研究中，提出了一种将离散元方法和孔网络模型相结合的数值程序，以将物理上具有代表性的孔结构与颗粒的几何特征联系起来，并快速预测颗粒组件的宏观流动特性。应用该数值程序研究了颗粒梯度和几何形状对各向同性压缩下粒状土壤的孔隙特性和保水曲线的影响。结果表明，均匀系数（C _u）的粒径导致较低的孔隙率。孔隙率首先降低，然后随着颗粒的长宽比（AR）从1.00增加到2.50而增加，并在AR = 1.75时达到最小值。当C _u在1.00至2.16的范围内时，孔几何形状和连通性参数（包括孔和喉部直径，孔间距和配位数）的标准偏差和平均值呈现线性相关性。响应于C _u和AR的变化，进气压力的对数随平均孔径的对数的增加而线性减小。较小的C _u导致较高的孔径变化会产生较低的拟合参数m 在范Genuchten方程中的保水曲线。