关键词: 颗粒形态, X射线计算断层扫描, 图像处理, 球谐函数分析, 形态参数

Abstract: Particle morphology is an important factor affecting mechanical properties of granular sands (especially the shear strength, dilation and critical state behaviours under low stress conditions), as well as particle crushing behaviours under high stress conditions. Therefore, in order to study the morphological effects of sand particles, it is the prerequisite to accurately reconstruct and quantitatively characterize the three-dimensional (3D) morphological features of sand particles. In this study, the 3D morphological information of Leighton Buzzard sand and decomposed granite sand particles was obtained by means of high-precision CT scanning and a series of image processing techniques. The spherical harmonic (SH) function sequence was then used to reconstruct the accurate 3D particle morphology. Furthermore, the particle volume calculated by SH analysis was used to validate the efficiency of SH reconstruction of the 3D particle morphology. Based on the SH-reconstructed particle surface, we proposed practical methods to calculate the surface area, the surface curvature distribution and the 3D dimensions of the sand particles, and further calculate the 3D sphericity, roundness and elongation of the sand particles. The results show that the SH-reconstructed particle surface agrees well with the real sand particle including the general shape and surface texture when the order of the SH function reaches 15. In addition, the particle morphology of Leighton Buzzard sand is more regular and smooth due to geological action of water transportation and abrasion, while the particle morphology of granite residual sand is more complex and rough due to physical weathering and denudation. However, both two geologic actions have no significant effect on the 3D dimension ratio of the sand particles.

Key words: particle morphology, X-ray micro-computed tomography, image processing, spherical harmonic analysis, morphological parameters