CONTINUOUS CUTTING
rectangular cross section tunnel .
The MDM5000 ( standing for Mine Development Machine ) has been designed for use in underground mining in rock up to 200 MPa UCS , making it particularly useful for long access tunnels and development drifts . It has dimensions of 5 m x 4.5 m and can excavate a flat tunnel invert for immediate use by rubbertyred vehicles , according to the company .
Robbins has made significant progress with the MDM5000 ’ s first mine site application , having , by September 2021 , clocked up more than 1,700 m of advance at rates up to 52 m in one week and 191 m in one month at the Fresnillo silver mine in Mexico . Such numbers make it significantly faster than the equivalent drill and blast excavation method , which is all the more impressive considering it had been excavating in andesites and shales with quartz intrusions that , according to the company , have defeated heavy roadheaders in earlier tunnelling attempts .
Fresnillo , in reviewing the machine ’ s progress across 2021 in its most recent annual report , said the MDM5000 ’ s contribution was less than expected due to trialling the unit in a production area that featured “ less advantageous geomechanical characteristics ” than those found in development areas .
Yet , the mining company said it planned to relocate the MDM5000 to a development area , anticipating that performance would return to previous high development levels following this .
MTB 2.0
Another traditional TBM variant that is making progress is Master Drilling Group ’ s Mobile Tunnel Borer ( MTB ).
This modular horizontal cutting machine is equipped with a full-face cutter head with disc cutters adapted from traditional TBMs . Unlike these traditional machines , it is designed to work both on inclines and declines , with the ability to navigate around corners and construct 5.5-m diameter decline access tunnels .
During Master Drilling Group ’ s 2021 results presentation , Director , Koos Jordaan , confirmed that the company had started tunnelling work on an exploration decline at Anglo American Platinum ’ s Mogalakwena PGM mine in South Africa , using the MTB .
The machine has since completed a “ tight horizontal curve ” on this project , Jordaan acknowledged in Master Drilling ’ s most recent half-year results .
Having initially been tested in a quarry in Italy in soft rock , the MTB made the trip back to South Africa to start work on a 1.4 km project at Northam Platinum ’ s Eland platinum group metals operation in South Africa , in harder rock . This project was terminated in March 2020 due to the COVID-19 pandemic .
Last year , however , the company announced it had signed an agreement with Anglo American Platinum to deploy the MTB at Mogalakwena as part of a turnkey contract to sink an exploration decline .
While this project is ongoing , Jordaan said the company is also working on designs for a second-generation MTB that would cater to the industry need to safely and quickly establish twin declines for mine access .
He said the company envisioned future projects using two MTBs simultaneously to establish traditional twin declines for access to underground mines for fast access from “ A-to-B ” and a quick turnaround to steady-state mining operations .
The company is also carrying out early-stage work with Element Six and the De Beers Group on cut and break technology which , when applied in tandem with the use of the MTB , could enable even more continuous cutting applications .
Element Six , as a company , was established to harness the unique properties of synthetic
Master Drilling recently commenced tunnelling work on an exploration decline at Anglo American Platinum ’ s Mogalakwena PGM mine in South Africa , using the MTB diamond ( polycrystalline diamond or PCD ) and tungsten carbide to deliver super materials that improve the efficiency , performance and reliability of industrial tools and technology . One of the obvious applications for the super materials is in hard-rock cutting where OEMs have trialled PCD materials .
Jordaan said the company could leverage cut and break technology with MTBs to create flat floors and breakaways , allowing the circular MTB to continue cutting the face without stoppages .
Adapting the TBS
Another machine that is billed as being able to provide continuous cutting operations in hardrock applications is the Tunnel Boring System ( TBS ).
Formerly known as the Mobile Miner 55V , this machine has been designed to continuously make reinforced tunnels with a size of 5.5 m x 5.5 m , down to a radius of 65 m with a flat floor .
The only unit that has been manufactured passed down from Epiroc to Bergteamet AB , and is now being leased to Dividend Industries AB , through former Bergteamet CEO , Urban Holmlund ’ s company , Urban Holmlund Konsult AB .
Dividend Industries is a capital and human aggregation of businesses focused on engineering , the building industry and building materials , food processing industries , wood and furnishing , specific products and services .
Its plans for the TBS are tied to the work it is carrying out with Sweden ’ s Uppsala University , Slovakia-based renewable energy-focused company VUNAR and other partners on “ cost effectively penetrating the Earth ’ s crust ”.
President Alexander Zvrskovec told IM last year that the company had planned to use the TBS in two potential applications in Sweden and Slovakia under the group ’ s wide remit .
He told IM more recently that the company was creating an international consortium with the ambition to penetrate the earth ’ s crust beyond 3.5-km depth to reach a petro-thermal environment in crystalline bedrock .
This endeavour will require the establishment of both shafts and tunnels , with the TBS used for the latter . The partners are exploring the potential use of new tools , based on electropulse fragmentation , as attachments for the front of the TBS to replace the cutting wheel and enable horizontal block excavation , Zvrskovec said .
On this consortium , he said : “ The members of the consortium include several universities , industries and mining authorities in several EU countries . We aim to gather and educate specialists to run our TBS system and to investigate its capacity for different purposes . Our long-term ambition is to create a settlement within these depths .” IM
18 International Mining | NOVEMBER / DECEMBER 2022