Mt Rawdon Gold Mine located approximately 100 km inland from Bundaberg is a conventional truck and shovel type open cut gold operation. The operation is 100 % owned by Equigold NL with the mining processes being contracted out. The thesis “Mine to Mill Optimisation at Mt Rawdon Gold Mine” will take into consideration the effects of varying blasting practices on downstream process such as material handling, crushing and minerals processing.
Data has been collected in the format of digital images taken after the blasting process, using these images a fragmentation size distribution for the material is established using the computer package, JK Split. Other computer-modelling programs such as the Kuz-Ram model incorporated into programmes such as 2DBench and JK Blast Management System can be used to determine the size distribution when blasting parameters are varied. By repeating this process with a number of different parameters, a close to optimal drill and blast design can be concluded. The basis for determining the best design will be the overall net value of the project, including; drill and blast, material handling, crushing and minerals processing.
The following table summarises the drill and blast design that has been determined to be most beneficial to the project and compares it to current drill and blast practices, both cases use a hole diameter of 127 mm.
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Essentially, the only drill and blast parameters that have been changed are pattern and stemming. The pattern has been changed from 3.9 x 4.5 m to 3.1 x 4.7 m, this has altered the burden to spacing ratio from 1.15:1 to 1.5:1, this change will increase fragmentation (Figure i) significantly without increasing the powder factor as drastically that maintaining the burden spacing ratio of 1.15:1 would have.
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In terms of cost, the increased fragmentation achieved by the optimized design will increase drill and blast costs by 23.9%, however these costs create potential for significant cost savings and increases profit in downstream processes. The downstream processes that benefit from increase fragmentation include; load and haul, crushing, milling, power consumption, mill throughputs, and less wear and tear on load and haul equipment and crushers. Drilling and blasting costs comprise less than 35% of total mining costs therefore an increasing drill and blast costs by 23.9% will be significantly outweighed by cost savings of 30% of more in the downstream process comprising the remaining 65% of mining costs.
This thesis addresses all aspects of Mine to Mill Optimisations and analyses the Mt Rawdon Gold Mine operations with respect to Mine to Mill Optimisations. The findings show that introducing a more intensive drill and blast design in order to increase fragmentation and increase net profit of the project has a high likelihood of probability under current constraints and rock types.
However, the mine is a relatively new mine and geological studies have indicated at greater mining depths the orebody is a highly complex system of extensive jointing and structures. This is discouraging for a Mine to Mill Optimisation line of thinking as under these conditions an increase in drill and blast intensity may not yield the same increases in fragmentation and may not provide the same benefits that can be currently achieved. None the less under current circumstances it is highly recommended that the proposal be further assessed and continued to be re-assessed in the future as this iterative process is the best form of blast optimisation.