CONTINUOUS CUTTING
Technical Services for Osisko Development Corp .
Osisko said : “ This equipment is engineered to mechanically cut the hard and abrasive rock mass and is expected to improve the development performance by 25 %, and to reduce costs by 50 % compared to traditional drill and blast development .”
Both roadheader and drill and blast development will be used for the Cariboo mines with an estimated monthly development rate of 200 m per face and 300 m with multiple faces with an average 11 km / y of development peaking at 16 km / y using two roadheader crews and 3-4 conventional crews . Mine production is based on longitudinal retreat long-hole stoping using a combination of cemented rock fill , uncemented rock fill and paste fill with 30 m sub-levels .
Vézina explained the company ’ s decision for choosing to use both roadheader and drill and blast operations at Cariboo .
“ At the start , our focus was on ensuring sustainable development rates , but , most importantly , safe development by reducing exposure of personnel to challenging ground conditions ,” he told IM . “ Our hope was to reduce the induce fracturing in the surrounding rock from conventional drill and blast and improve the drift ( tunnel ) profile and the overall stability of the drifts .
“ We expected to have potential gains on the productivity of the mine development and cost but were doubtful of achieving material cost savings .”
After testing an old roadheader at Bonanza Ledge and negotiating a trial arrangement with Sandvik based on reaching a 200 m / mth development rate ( for a 5 x 5 m drift ) with roadheader availability of 86 %, the company committed to purchasing two MT720 roadheaders for the trial .
These roadheaders are currently cutting rock between 50-70 MPa , with Osisko using a Sandvik bolting arm for improved safety and efficiency in mine development , in addition to elements of Sandvik ’ s Cutronic autonomous technology solution . Vézina said the company hopes to scale up to higher levels of roadheader automation down the line .
“ We are also pushing Sandvik to develop a fully-autonomous development process ( roadheader and truck ),” he added .
With Osisko confirming an order for a third roadheader at the operation – a Sandvik MT620 – it is already looking at other applications where these cutting machines could be used .
“ With our current knowledge , we have developed several other potential applications where we could use the roadheader ,” Vézina said . “ Rock cutting offers several other advantages over safety and cost reduction . On the environmental part , not blasting reduces the ammonia nitrate in the water and eliminates the resultant gas production , for example .”
David Hickson , Business Line Manager , MECU , Sandvik Mining and Rock Solutions , said Sandvik roadheaders had been sold into the global mining and tunnelling markets for many years , from as early as 1964 , but mining applications todate had been limited to room and pillar applications in coal , salt , potash and other soft rock minerals .
Hickson said there was potential for more of these machines moving into hard-rock applications like Cariboo .
“ We have seen an increase in enquiries and interest in using mechanical cutting versus conventional drill and blast ,” he said . “ With the rise in commodity prices , there is a need to access the orebody at a faster rate , and , with the correct utilisation of the roadheader in an appropriate application , this is possible .
“ Commodity prices aside , removing operators from the underground environment is driving the need for autonomous operations and our latest mechanical cutting technology is focused on making this a reality .”
Next gen MTB
Moving to the tunnel boring side of the business , Master Drilling and its Master Tunnelling division are in the process of preparing its Mobile Tunnel Borer ( MTB ) for a second decline application in South Africa .
Having had to cut short a performance validation project at Northam Platinum ’ s Eland mine in March 2020 due to COVID-19-related market uncertainties , the company , in August 2021 , announced it had been awarded a contract to deploy the MTB at Anglo American Platinum ’ s Mogalakwena mine in South Africa .
Master Drilling Executive Director , Koos Jordaan , told IM the MTB will be used to construct one of two underground exploration decline tunnels at the operation , with excavation
Master Drilling ’ s MTB will be used to construct one of two underground exploration decline tunnels at Anglo American Platinum ’ s Mogalakwena mine , with excavation likely to start in the March quarter and concluding in 2023 , according to Koos Jordaan
likely to start in the March quarter and concluding in 2023 .
When asked about the similarities between the two applications at Eland and Mogalakwena , Jordaan said : “ The next project will be similar to the previous one in terms of rock hardness , vertical curves , decline gradient , excavation size , etc . Changes include a surface high wall starting position , a horizontal curve and trucking rock chippings .”
Yet , the company is taking a different approach to the Mogalakwena project , based on a turnkey service provision that Master Drilling has used successfully in its raiseboring and exploration drilling projects before . This looks to provide support functions around a specialised service offering such as tunnel boring mine access , Jordaan explained .
“ This will include additional aspects of project management , engineering design , construction , logistics , civils , geotechnical drilling , etc ,” he said .
This approach aligns with Anglo Platinum ’ s strong environmental , social and governance programs , where , in particular , there is focus on supporting inclusive procurement , employment and development of “ doorstep communities ” within the scope of the exploration tunnel , Jordaan added .
It will also help Master Drilling improve on the results it previously achieved at Eland – where it completed a 130 m stretch of decline tunnelling over a three-month period .
“ At our previous project , Master Drilling achieved 6 m / d over a week with relatively limited face time ,” Jordaan said . “ Master Drilling would like to use this as a basis to improve repeatability and productivity on future operations .”
NOVEMBER / DECEMBER 2021 | International Mining 71