Optimal Design Blast Parameters for an Effective Rock Fragmentation

Abstract

Achieving the required fragment sizes with the maximum size (p100 value) being less than 1000 mm after blasting is a major challenge in the Newmont Ahafo South mine., Ghana. Blasting usually results in an excessive proportion of boulders which negatively affects productivity by increasing the time taken for loading, hauling, and crushing. It also increases the cost of operation because of secondary blasting, and the excess fines also result in the loss of gold. The objective of the study is to review the current blast design procedures adopted by Ahafo South Mines in order to identify the causes of the boulders and to optimise the design parameters, if necessary, in order to obtain the required fragmentation for the mine. Quality assurance and quality control were done on the existing drilling and blasting procedures to identify the deficiencies, and optimised (modified) drilling and blasting parameters were obtained through a simulation using the Kuz-Ram model. Digital images from the blast shots were taken and analysed using the Orica Shotplus software, and the average result of the two blocks was compared to results from the Kuz-Ram model. Because of the relative ease of predictability of the Kuz-Ram model, it was used to predict the blast design parameters that would yield optimal fragmentation without any boulder. The image analysis showed an average variation of 16.4% of the expected fragmentation, which aided in obtaining an expected maximum size of 603.4 mm, other than 517 mm from the prediction model. Thus, the Kuz-Ram model was used to predict spacing and burden of 4.2 x 3.5 m (with a powder factor of 1 kg/m³) as the optimal values for the blast design.

Keywords: Optimisation, Drilling, Blasting, Fragmentation, Kuz-Ram, Model