CONTINUOUS CUTTING
TBM is : ‘ how am I going to get it underground ?’ – miners are starting to re-think their mining process to best leverage the technology for sustainability and productivity benefits , according to Home . Developments such as the MDM are , at the same time , offering an alternative to standard TBMs designed for the civil construction sector .
“ The mines don ’ t want round tunnels , and , of course , that ’ s what we are best at ,” Home said . “ So , to address that we developed our unique MDM rectangular TBM to meet mining halfway – it gives you a nice flat floor on which you can drive all your vehicles efficiently and immediately , and it produces a defined space without the typical 15-20 % of overbreak with conventional drill and blast .”
The increased advance rates offered are partly due to the machine ’ s continuous progress , unlike drill and blast operations where crews must exit the tunnel during blasting for safety . In addition , simultaneous ground support installation further increases overall advance rates compared with drill and blast operations that must install ground support sequentially .
“ One reason we are working with Fresnillo is their commitment to work closely with us on the project and the machine ’ s central role in their future plans ,” Home said . “ Often in the past major mining houses have reached out wanting to work on a machine purely from an R & D standpoint – but for a complex machine like this , it isn ’ t enough .
“ We don ’ t want our machine to be sitting in a corner as an expensive experiment .”
At Fresnillo , Robbins has shown the required excavation rates are achievable ; and the scope of project has been widened significantly due to its performance .
At the start , the miner wanted a straight 4.5 km tunnel only . This evolved into boring a 360 ° spiral to end above the original tunnel – a distance of over 4 km . The machine is to then be backed up to the original tunnel and continue driving straight ahead .
Like any project of this type there have been challenges – notably dealing with a lot of ore veins , which slowed progress due to unstable rock zones and high water inflows – but the machine remains at the heart of the operation .
“ When the rock was consistent , we went up to three times faster than drill and blast – over 185 m in a month , versus 60 or 70 m ,” Home said .
While the MDM5000 has gone some way to proving itself in underground mining , Robbins sees it as just one component of a new development approach .
A multi-faceted solution for underground mine development would see the use of Robbins shaft boring machines for ventilation and mine access , as well as TBMs and conveyors to directly mine
Holistic cutting
CMIC is continuing to advocate for mechanical cutting as one of a number of technologies to achieve better operational , environmental and financial performance for its members and the wider industry .
Having helped establish the collaboration between Komatsu and Vale at the Garson mine in Canada – which is now deemed a full CMIC mechanical demonstration project ( see Changing the cutting dynamic section ) – CMIC has now signed up several miners and another OEM for a second demonstration project that could soon be cutting rock at an operating mine .
At the same time as this , it is busy leveraging its industry contacts and a wide scope of projects within the CMIC ecosystem to help reduce the size and scale of tailings storage facilities across the globe .
In this pursuit , it is working with the International Council on Mining and Metals ( ICMM ) as an Associate Member on the technologies and processes to reduce tailings generation in the industry .
ICMM members have been exploring innovative approaches and technologies to minimise and ultimately eliminate tailings waste from the mine lifecycle for some time , and CMIC thinks it can bring something new to the table , Trevor Kelly , Innovation Manager – Mining , said .
“ When it comes to our mechanical cutting stream , we see this as a fundamental technology to confront the tailings generation challenge ,” he told IM . “ The ability to potentially predict and measure the product / chip size through accurate and concise rock cutting has a significant downstream impact on not only the processing plant , but also the generation of tailings .”
This aligns with a broader focus for CMIC on moving the underground drill and blast platform process to a continuous – as opposed to batch – process . In this pursuit , MRE is seen by CMIC as being the first key platform technology .
“ MRE machines represent a shift in technology platform that happen to be electric-based ,” Kelly said . “ It enables additional technology platforms to be ‘ bolted ’ on the back end ( ie the particle sizes produced by MRE are ideal for sensor-based ore sorting ). Once this material is ‘ sorted ’, it allows significant waste streams to remain underground , thus having a direct impact on overall energy consumption ( less material = less energy for transportation to surface , crushing , grinding , etc ).”
Kelly and CMIC are in the process of developing a roadmap for these technologies to pitch to ICMM members , but he sees the potential for it spurring on more interest in mechanical cutting in the future .
the orebody and transport material . The TBMs would be lighter , more mobile and able to bore inclines , according to the company .
Robbins is also working on vertical shaft boring developments , with Home saying the company is looking to finalise an order for such a machine “ in the coming months ”.
He added : “ And we are doing some remotely operated incline boring with TBMs on hydro projects , which can have some application in mining . The continuous miners out there have done well in soft potash but are roadheader technology limited in harder rock . There is no question that , with disc cutters , we can handle up to 300 MPa rock – you slow down but you don ’ t stop when using disc cutters .”
And for long , straight declines in mining there is huge potential , according to Home . This is especially so with autonomous ore haulage operations that consider using two declines to allow for one-way traffic loops of autonomous trucks .
He concluded by saying the industry is becoming more progressive in its view of mechanised cutting technology , with free trials leading to a decision to buy a new machine or not .
“ Today , many more mines are working with suppliers to achieve the best solution together but with more of an upfront partnership to share both risk and benefits ,” he said .
Ready to adapt
Epiroc is hopeful that 2022 will be the year its Mobile Miner advances further .
Having previously lined up mine site trials for its 40V and 22H machines , the company ’ s ambitions , like many in this space , have been hit by COVID-19-related disruption .
Its 40V machine , suitable for 4 x 4 m advances , is due to arrive at Hecla ’ s Lucky Friday silver-lead-zinc mine in Idaho , USA , in 2022 , where it is expected to help the miner develop a fully mechanised underhand mining method that gets around the seismicity issues previously experienced operating at the mine .
Hecla said in its annual report : “ Work has been underway since 2017 to develop a fully mechanised underhand method which would utilise a remote vein miner ( the Mobile Miner 40V ) for mechanical excavation . Fabrication of the remote vein miner was completed in 2019 . Testing and modification of the machine at the manufacturer ’ s facilities proceeded in 2020 but
74 International Mining | NOVEMBER / DECEMBER 2021