CONTINUOUS CUTTING
Face time
Komatsu ’ s MC51 is able to cut within 50 mm of plan , with the resultant excavations exhibiting high tunnel quality and a reduction of over break
working with Anglo American as part of its FutureSmart Mining™ vision , with the 22H currently in South Africa . There had been plans to include the machine in a test that involved a combination of both mechanical rock cutting and preconditioning of the rock .
Epiroc told IM : “ Epiroc are working closely with its partner Hecla on finding the best solution exiting the Mobile Miner 40V project and securing potential value . In regard to the Mobile Miner 22H , we are committed to work with Anglo American in finishing the ongoing tests in South Africa before setting the details for our exit .”
Required improvements in safety and productivity , alongside increasingly complex orebody extraction plans , are the big factors pushing reserve-starved mining companies towards mechanised mine development , Dan Gleeson writes
The biggest news to come out of this sector in 2024 is undoubtedly the announcement that Epiroc will phase out its Mobile Miner concept line within 2024 . The decision comes 14 years after the company ( under Atlas Copco ) initiated it .
The Mobile Miner concept line was developed and demonstrated in close partnership between Epiroc and selected partners , including Anglo American . Upon launch , Epiroc invested in the development of three units : the 22H , 40V and 55V . In the years that have passed , this has been refined into a two-product family , the 22H and 40V , both of which have been designed for specific mining methods and constraints .
These Mobile Miners , which leverage standard disc cutting technology , consist of two major parts : the rear “ power unit ” and the front “ miner ”. The miner incorporates the cutterhead and everything needed to excavate ore ; the power unit contains all the motors , pumps , ground support and control systems . Each unit is roughly 10 m in length , with the two parts connected by an articulation joint to improve manoeuvrability for negotiation of tight corners as well as minimise vibration in the operator ’ s cab .
The largest Mobile Miner is the 40V , which is typically used in small-to-medium-sized tunnels and cut-and-fill mining requiring 4 m x 4 m advances . The V indicates the cutter head is placed vertically – as opposed to the H of the 22H , placed horizontally – with the stated advance rate of the machine being 10-15 m / d depending on the rock type .
Reminiscent of a traditional TBM in appearance , the first 40V was scheduled to be deployed at Hecla Mining ’ s Lucky Friday mine in Idaho , USA , after extensive work by both Hecla and Epiroc to tailor the machine to the veins that would be mined at the seismically active operation . The successful application of a new mining method – Underhand Closed Bench – at the mine recently led to Hecla deciding against the machine ’ s use at Lucky Friday .
The 22H – with certain adaptations – was previously tested at the Twickenham PGM mine in Limpopo Province , South Africa , where it advanced at over 10 m / d in 140-150 MPa UCS rock in a trial that was curtailed due to the mine being placed on care and maintenance . It is designed for low-seam or low-profile mining where tunnels as low as 2.2 m are required .
Since the trial at Twickenham , Epiroc has been
Robbins and full-face engagement
Robbins ’ tunnelling experience has been leveraged in mining over the decades , yet today most of the hard-rock mechanical rock excavation talk about the company is linked to its MDM5000 .
This machine , which uses disc cutter technology proven on traditional circular machines , can excavate rock up to 200 MPa in rectangular cross section tunnels with dimensions of 5 m x 4.5 m . This is thanks to a reciprocating cutterhead able to exhibit a swinging motion .
In addition to the cutting element , continuous ground support is placed immediately behind the cutterhead in a pattern that is mine-standard , according to Robbins . Ground support and installation of utilities such as piping , ventilation and lighting are carried out simultaneously to boring , with the MDM5000 providing a complete mechanical rock excavation system .
The ability to excavate a flat tunnel invert for immediate use by rubber-tyred vehicles is a key selling point of the technology , as well as a major differentiator to standard TBMs .
Robbins has a real-world mining trial to reflect on with the MDM5000 , having carried out more than 1,700 m of advance at Fresnillo ’ s flagship mine , in Mexico , up to September 2021 at rates up to 52 m in one week and 191 m in a month .
After hitting an unexpected fault zone which took the mine 18 months to grout-off , retract the MDM5000 and relaunch , Robbins took part of this time to make some refinements to the system . The MDM5000 has since restarted operations .
“ They ’ re back operating now ,” Lok Home , President of Robbins , told IM . “ There are some very positive steps being taken now at the mine . We are probe drilling ahead with core drilling and picking up faults or unexpected ground conditions before we start boring .
“ To pull the cores , analyse them , and plan the correct ground support and / or pre-grouting is
56 International Mining | NOVEMBER / DECEMBER 2024