Morphological analysis is a prerequisite step for studying the mechanical properties of unbound granular geomaterials through both laboratory experiments and numerical simulations. In this study, two typical geomaterials, e.g., ballast and cobble particles, were sampled for study. First, a systematic framework was established to acquire two-dimensional (2D) particle outline and three-dimensional (3D) morphology for statistical shape analysis. The photographic-based system was set up to acquire 2D images of particle projections from multiple surrounding directions, then the images obtained were used to reconstruct 3D particle morphology based on close-range photogrammetry. Second, in order to quantify particle shape at three different geometric scales, 6 well-acknowledged 2D and 3D geometry descriptors, i.e., aspect ratio, sphericity, convexity, roundness, regularity, and roughness were computed. Third, the probability distribution function (PDF) of shape descriptors were fitted with different functions. Finally, 2D and 3D shape descriptors were statistically compared and the relationships between them were revealed by analyzing their cumulative distribution functions (CDFs).

形态分析是通过实验室实验和数值模拟研究未结合的颗粒土工材料力学性能的前提步骤。在这项研究中，取样了两种典型的土工材料，例如压载和卵石颗粒进行研究。首先，建立系统框架以获取二维（2D）粒子轮廓和三维（3D）形态，以进行统计形状分析。建立基于摄影的系统以从多个周围方向获取粒子投影的2D图像，然后将所获得的图像用于基于近距离摄影测量法重建3D粒子形态。其次，为了量化三种不同几何尺度下的颗粒形状，我们使用了6种公认的2D和3D几何描述符，即长宽比，球形度，凸度，计算圆度，规则性和粗糙度。第三，形状描述符的概率分布函数（PDF）具有不同的函数。最后，对2D和3D形状描述符进行统计比较，并通过分析它们的累积分布函数（CDF）揭示它们之间的关系。