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.