Blast-induced Rock Fragmentation Analysis Using Image Analysis Method in Bashmagh Hashtrood Copper Mine

Abstract

Blasting is the most effective excavation technique to extract hard rocks. In open-pit mines, the bench blasting technique is used to prop the in-situ stones and crush them to the desired size. When designing a blast, the most effective method to achieve the desired fragmentation is selected. The degree of fragmentation plays an important role in controlling and reducing the costs from loading, hauling, and crushing. The blast is the first step to reduce the rock size, followed by crushing and grinding. The efficiency of this operation depends on the distribution of the exploded rock sizes. Therefore, it is essential to measure and analyze the fragmentation of rock masses. The sieve analysis method is accurately direct but incurs costs, is time-consuming, and difficult as an inclusive experimentally mathematical model to encompass all mining features is lacking. However, post-blast rock gradation using the image analysis method is easy, fast, and inclusive.

As data from image analysis indicate, D₈₀, D₅₀ and D₂₀ values for the blast-induced fragmented rocks were 20, 13, and 7 cm, respectively; also, with increasing the size, the difference of the cumulative percentage passing of Kuz—Ram and image analysis increased. According to the validation for the three 1.5-, 5.5- and 13-ton specimens of the three exploded faces, it was noted that as the tonnage of the specimens increased, the difference of image analysis increased as compared to the sieve analysis of each specimen. This difference was found to be greater in three 12.7, 19- and 31.5-mm dimensions.