Quantitative analysis of shapes and specific surface area of blasted fragments using image analysis and three-dimensional laser scanning

Abstract

Blasted fragments, which are mainly characterised by the size, shape, and specific surface area (SSA), play a pivotal role in downstream mining processes. In this study, the shapes and SSAs of different types of blasted fragments at three quarries in China were investigated. Wide grading blasted fragments of limestone, tuff, and granite were randomly selected and classified into five categories according to their three-dimensional (3D) shapes. The sizes, shape parameters, and SSAs of the blasted fragments were determined using image analysis and 3D laser scanning, and their variation laws with respect to the lithology and fragment size were analysed. The results indicated that approximately 82%, 74%, and 79% of the fragments were hexahedron, pentahedron and tetrahedron in the limestone, tuff and granite muck piles, respectively, and these three types of fragments can be modelled as spheres. The limestone fragments were the most spherical, and the tuff and granite fragments were more angular. Under the same lithology, hexahedron, pentahedron, tetrahedron, and flat and elongated particles became more angular successively, while the surface texture remained almost same. The shape parameters of blasted fragments were related to the fragment size. Furthermore, the SSA reflected the combined effects of the size and shape of the blasted fragments. The SSAs of limestone, tuff and granite fragments decreased according to a power function at different rates as the size increased. The results can be helpful for improving the accuracy of the fragmentation size distribution obtained via image analysis and the calculation of fragmentation energy in blasting.