A Trade-Off Study Between Drill Blast Operations and Reef Boring Method

摘要

With increasing depths of mining, difficult reef geologies, reduced overall mine productivity, as well as the increasing cost lines associated with mining in the narrow tabular property; the current blasting related mining methods prove to be less efficient. This is owing to low efficiency, higher effect on the surrounding rock, possible fly rock, dilution, personnel in danger line and production of toxic gases, etc. These challenges have resulted in a 13.5 (101.3 tonnes) and 2.9 (262.9 tonnes) decrease in gold and platinum production, 14 and 2.6 increase in gold and platinum costs and the rate of change in safety has started to flatten out. Several recent studies emphasize the development and utilization of non-explosive techniques of mechanical rock cutting that are integrated into continuous mining systems, and one of these techniques is reef boring. The work is aimed at determing the most suitable mining method between blasting technique methods (conventional B and P, conventional breast, mechanised B and P, and mechanised breast) and rock cutting technique method (reef boring which involves the drilling of narrow tabular reef and extracting the chippings for processing). The most suitable method is determined through a trade-off study. The trade-off study (mining method evaluation) was conducted through the use of simulations based on BME (Basic Mining Equations) and BFE (Basic Financial Equations) calculations, Risk assessments, Trade-off analysis: weighing, scoring, and comparisons of the mining method. The inputs of the study were derived from the literature survey that was conducted on different miningmethods. The background information gathered on these mining methods focussed on ore extraction, material handling, support, labour, equipment, and benefits challenges of each mining method. Using that background information together with mine benchmarking, a mock mine was created with the following orebody characteristics: thickness of 1.1 m, dipping at 15°, and an average grade of 4.12 g/t at a depth of 1.1 km. This ore deposit was extracted using all five mining methods investigated. The mining parameters for each mining method were based on the literature study information and first principles. The trade-off analysis was based on the selection criteria that includes production, cost, safety, dilution percentage, extraction percentage, flexibility, and automation. Based on the results, reef boring method produces the highest tonnages of 10 651 oz/month, has the highest profit of R303 million/month, highest NPV of Rl 423 million, highest IRR of 88, and highest ROCE of 296. Due to these factors, the reef boring is the most profitable mining method compared to drilling and blasting methods. Also, it has the least dilution percentage of 2 and the highest extraction percentage of 98. The reef boring method has the least number of employees on the face (10 people), fewer hazards are associated with the equipment and the reef boring machine causes the least disturbance on the surrounding rock. Hence, it is the safest method with maximised automation. However, even though the reef boring method is more feasible in the paper, practically for high performance the machine should be able to drill 18 h per hole and extract 1000 m and above.