Review of the Ahafo South Mine blasting procedures to achieve zero boulders

Abstract

Obtaining a good fragmentation for every blast remains an ever-important discussion in the mining parlance as it is the first step towards mineral recovery. Achieving the required fragment sizes with the maximum size (p100 value) being less than 1000 mm after blasting is a major challenge in Newmont Ahafo South Mine. Blasting usually results in excessive proportion of boulders which negatively affect productivity by increasing the time taken for loading, hauling, and crushing. It also increases the cost of operation because of secondary blasting and the fines also result in loss of gold. Helping the Mine achieve its initiative of zero boulders will positively impact productivity and reduce the cost of operation. 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 optimize the design parameters if necessary, in order to obtain the required fragmentation for the Mine. For this reason, a quality assurance and quality control were done on the existing drilling and blasting procedures to identify the mistakes and optimized (modified) drilling and blasting parameters was obtained through a simulation using the Kuz-Ram Model. Digital images from the blast shots were taken and analyzed using the Orica Shotplus software and the average result of the two blocks were compared to results from the Kuz-Ram Model. Because of the Kuz-Ram model’s strong predictability, 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 as 603.4 mm other than the 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 blast design parameter to achieve the Mine’s Initiative