2014 Volume 70 Issue 2 Pages 265-274
This paper describes the three-dimensional (3D) grain shape characteristics of some standard sands and its relation to the granular mechanical properties such as void ratio extent and shear strength. A x-ray micro CT at SPring-8 was employed to obtain CT images of Toyoura sand, Hostun sand, Ottawa sand, Ticino sand, SLB sand and glass ballotini. The CT images were analysed by an originally-developed image processing to identify 3D shape of each grains, and then the identified surface data were converted to STL surface mesh models by a meshing software (MeshLab). Then we calculated some shape indices such as the aspect ratio, the elongation ratio, the flatness ratio, sphericity and Krumbein's sphericity. Two types of indices based on ellipsoidal properties are newly proposed: (1) surface area ratio to ellipsoid, and (2) volume ratio to ellipsoid. The calculated indices are compared by means of their correlation with respect to void ratio characteristics and shear strength. As a result, the void ratio extent showed high correlation with it is found that the void ratio extent, and shear strength were highly correlated with the volume ratio to ellipsoid, and both of the aspect ratio and the volume ratio to ellipsoid, respectively.
