Minnovare identified the potential to improve production drilling outcomes in underground long-hole stopes through the adaptation of new technology which was under ongoing development. An approach to Evolution Mining resulted in the companies agreeing to a collaborative agreement to further develop the technology for use on underground long-hole drilling equipment.
During a period of six months in FY2018, a series of trials were conducted to compare drilling accuracy using two different methodologies and the subsequent impact this had on ore dilution. Testing was conducted at Cracow underground gold mine in Queensland, Australia. The drill rig’s existing setup/alignment process was compared to the new technology system with the following observations:
• Using the existing process only 20% of holes surveyed recorded toe points within the +/ 300mm (11.8in) tolerance blast-hole deviation.
• The new technology was proven to limit rig setup/alignment error, reducing average blasthole deviation and increasing the number of holes drilled within tolerance by 160%.
The increased accuracy reduced stope dilution by reducing over-break of subgrade ore:
• Stopes drilled using the new technology recorded 62.6% less average dilution. • This contributed to an overall reduction in dilution for the full year (FY18) of 5 percentage points compared to FY17 - from 22% to 17% (a net decrease of 22.7%).
• With the system implemented as standard practice following results of the FY18 trial and continued success, overall dilution for full year FY19 showed continued reduction to 12%
Evolution has continued use of the new technology at Cracow, where the improved accuracy has allowed the extraction of narrower stopes where drilling accuracy is critical. Evolution has also deployed the technology at the Mungari operation and has stipulated that the contractor use the technology at the Mt Carlton operation, which is currently under development. Future implementation of the Development Optimiser system should be verified by commencing additional trials to include a larger data base for validating the initial trial results.