CONTINUOUS CUTTING AND RAPID DEVELOPMENT
The design for the Epiroc Mobile Miner 22V wIll remain the same for the latest deployment at an Anglo American underground PGM operation , but the cutter head will be adapted to the geology at hand
“ Having said that , we have been in discussions with customers during this period and there are conceptual designs of larger versions of the 40V – almost a 50V ( 5 m x 5 m advances ) – which would be more suitable on a conceptual level for the industry .”
While the 40V is very much designed around Hecla ’ s Lucky Friday narrow vein application , most potential customers are looking at the more traditional , square cutting application , he said .
Welcome to the revolution
COVID-19 aside , the rationale for leveraging mechanised cutting technologies for mine development remains . Dan Gleeson gets updates on the major industry projects the
Ayear is a long time in any industry and , in
mining ’ s mechanised cutting sector , a lot has changed in the almost 12 months since IM delved below ground to check the pulse of this evolving space .
There have been plenty of comings and goings as the onset of COVID-19 has affected industry projects , but what has remained is the conviction there is a place for cutting machines in both hard and soft rock , with the potential to eventually compete with drill and blast in the mine development arena .
Unfinished business
As Epiroc continues to push forward developments with its Mobile Miner 40V ( destined for Hecla Mining ' s Lucky Friday mine in the US ), it is expecting a new mine deployment for its Mobile Miner 22V .
Typically used in low-seam or low-profile mining when a tunnel as low as 2.2 m is required , the 22V has previously been put to the test over an 18-month period at Anglo American ’ s Twickenham PGM mine in Limpopo Province , South Africa . During this trial , the unit advanced at over 10 m / d in 140-150 MPa rock hardness .
Marcus Eklind , Global Business Line Manager - Mechanical Rick Excavation at Epiroc , told IM last year that Epiroc and Anglo were hoping to identify another test site for the machine in the near term .
COVID-19 delayed this process , yet the two companies have now agreed on a new site for a trial , with Eklind confirming it was another of the miner ’ s PGM operations in South Africa .
“ This is now settled and the current time plan is that we will start cutting in the first ( March ) quarter of 2021 ,” he said .
In terms of changes to the 22V unit for the upcoming deployment , Eklind said the design remained the same but the cutter head had been adapted to the geology at hand .
“ It is the same machine , but there is a new set of segments that mount onto the cutter head to fit the geological conditions of the mine ,” he said . “ It ’ s a bit like in raiseboring where you dress your cutter head differently depending on the conditions it will be cutting in .”
He concluded on this trial : “ As you know , during the Twickenham trial , the mine went into care and maintenance before we could finish the production tests . Both ourselves and Anglo were encouraged by the results we had achieved to that point , but felt we needed to further prove the concept .”
Speaking of concepts , Eklind was keen to clarify a comment he made to IM last year on future design developments for Epiroc Mobile Miners being focused on “ actual rock cutting ” as opposed to the other many ancillary elements that come with mine development .
“ My comment on the cutting focus is really referencing the 55V that was designed together with Rio Tinto ,” he said . “ This machine is virtually a ‘ tunnelling factory ’ ( there is shotcreting , primary and secondary rock reinforcement , etc ).
“ The 40V we have designed for Hecla is more in line with the
optimal Mobile Miner design .
“ In all designs , we will most probably always have
some primary rock support ; I don ’ t think we will have only rock cutting – we can put up mesh and bolting with the 40V , for instance .
TBM and MTB
Over the last year , there has been mixed results for two companies pushing adaptations of conventional tunnel boring machines ( TBM ) for hard-rock applications .
Fresnillo , in looking to expand its namesake mine in Mexico , has partnered with tunnelling specialist Robbins , applying its TBM technology to develop the new San Alberto orebody at the underground mine .
During the company ’ s 2019 Capital Markets Day , Fresnillo said the $ 22.7 million San Alberto project , using a Robbins MDM 5000 , would ramp up to a 300 m / mth development rate at the start of this year , with the TBM intended to carry out 11 km of development in total .
From an image of the Robbins MDM 5000 released by Fresnillo , the machine appears to be a variation on traditional TBM technology designed for hard-rock mining using a unique cutting head design to create a uniform rectangular tunnel profile .
In Fresnillo ’ s September quarter results , the miner said year-to-date development rates remained at a similar level to 2019 , with a contractor hired at the end of 2019 , together with the start-up of the TBM , mitigating the negative impact of higher absenteeism related to COVID-19 .
From an image of the Robbins MDM 5000 released by Fresnillo , the machine appears to be a variation on traditional TBM technology designed for hard-rock mining using a unique cutting head design to create a uniform rectangular tunnel profile
International Mining | NOVEMBER / DECEMBER 2020