Tag Archives: Tunnel boring machine

AngloGold Ashanti confirms caving plans in Colombia

The Massmin 2020 crowd got a glimpse of just what will be required to build Colombia’s first underground caving mine during a presentation from AngloGold Ashanti’s Lammie Nienaber this week.

Nienaber, Manager of Geotechnical Engineering for the miner and the presenter of the ‘Building Colombia’s first caving mine’ paper authored by himself, AngloGold Ashanti Australia’s A McCaule and Caveman Consulting’s G Dunstan, went into some detail about how the company would extract the circa-8.7 Moz of gold equivalent from the deposit.

The Nuevo Chaquiro deposit is part of the Minera de Cobre Quebradona (MCQ) project, which is in the southwest of Antioquia, Colombia, around 104 km southwest of Medellin.

A feasibility study on MCQ is expected soon, but the 2019 prefeasibility study outlined a circa-$1 billion sublevel caving (SLC) project able to generate an internal rate of return of 15%. Using the SLC mining method, a production rate of 6.2 Mt/y was estimated, with a forecast life of mine of 23 years.

The MCQ deposit is a large, blind copper-gold-silver porphyry-style deposit with a ground surface elevation of 2,200 metres above sea level (masl, on mountain) and around 400 m of caprock above the economic mineralisation.

Due to the caving constraints of the deposit, the first production level to initiate caving (undercut) is expected to be located around 100 m below the top of the mineralisation at 1,675 masl (circa-525 m below the top of the mountain), with the mining block extended around 550 m in depth (20 production levels at 27.5 m interlevel spacings).

The main ore transfer horizon is located 75 m higher in elevation than the mine access portals at 1,080 masl and the proposed valley infrastructure. The initial mining block will be accessed by twin tunnels developed in parallel for 2 km at which point a single access ramp will branch up towards the undercut; the twin tunnels will continue another 3.7 km to the base of the SLC where the crushing and conveying facilities will be located.

The company is currently weighing up whether to use tunnel boring machines or drill and blast to establish these tunnels.

Nienaber confirmed the 20 level SLC panel cave layout would involve 161 km of lateral development and 14 km of vertical development. There would be six ore pass connections on each level, four of these being ‘primary’ and two acting as backups. The crusher would be located on the 1155 bottom production level.

Due to the ventilation requirements in Colombia the mining fleet selected for Quebradona is predominantly electric, Nienaber said, adding that the units will initially be electric cable loaders powered by 1,000 v infrastructure.

Fourteen tonne LHDs were selected for the production levels based on their speed, bucket size (enables side-to-side loading in the crosscut and identification of oversize material) and cable length, the authors said. On the transfer level, 25 t loaders were specified to accommodate the shorter tramming lengths and limited operating areas (there are a maximum of two loaders per side of the crusher due to the layout).

As battery technology improves in the coming years, the selection of loader sizes may change as additional options become available, according to the authors.

The selection of the present Sandvik fleet was predominantly based on the electric loaders and the OEM’s ability to provide other front-line development and production machines required to undertake SLC mining, the authors said.

This decision also accounted for the use of automation for the majority of production activities, with the use of a common platform seen as the most pragmatic option at this stage.

It has also been proposed that the maintenance of the machines be carried out by Sandvik under a maintenance and repair style contract since there is a heavy reliance on the OEM’s equipment and systems.

An integrated materials handling system for the SLC was designed from the ore pass grizzlies, located on the production levels, to the process plant.

Due to the length of the ore passes (up to 500 m), and the predicted comminution expected by the time the rock appears on the transfer level, larger than industry standard grizzly apertures of 1,500 mm have been selected.

The design criteria for the underground crusher was that it needed to reduce the ore to a size suitable for placement on the conveyor belt and delivery to the surface coarse ore stockpile, after which secondary crushing prior to delivery at the process plant will be undertaken.

Assuming the maximum size reduction ratio for the crusher of circa-6:1 at a throughput rate of 6.2 Mt/y, a 51 in (1,295 mm) gyratory crusher was selected. This crusher is also suitable to support block cave mining should the conversion of mining method occur, according to the authors.

The process plant will include high pressure grinding rolls as the main crushing unit on the surface, supported by a secondary crusher to deal with oversize material. The ore then feeds to a ball mill before being discharged to the flotation circuit.

The gold-enriched copper concentrate will be piped to the filter plant for drying and the removal of water down to a moisture content of 10%, according to the company, while the tailings will be segregated to pyrite and non-pyrite streams before being distributed to one of two filter presses.

Dry stacking of the tailings will be used, with the pyrite-bearing tailings being encapsulated within the larger inert tailings footprint.

With the feasibility study due before the end of the year – and, pending a successful outcome – the proposed site execution works could start in the September quarter of 2021, Nienaber said.

Vale teams with Komatsu and CMIC on ‘revolutionary’ hard-rock cutting project

Vale, in 2021, is due to embark on a major hard-rock cutting project at its Garson mine, in Sudbury, Canada.

Part of the mechanical cutting demonstration within the CMIC (Canada Mining Innovation Council) Continuous Underground Mining project, it will see the company test out a Komatsu hard-rock cutting machine equipped with Komatsu DynaCut Technology at the mine.

With an aim to access the McConnell orebody, as well as provide a primary case study for CMIC members to learn from, all eyes will be on this Sudbury mine in the June quarter of 2021.

Vale plans to demonstrate the ability to cut rock in excess of 250 MPa; cut at a commercial rate of more than 3.5 m/shift; quantify the cost per metre of operation and start to look at the potential comparison with conventional drill and blast development; assess the health, safety and environmental suitability of the mechanical rock excavation (MRE) process; and gain insight into the potential of an optimised MRE process.

Another Komatsu unit has already been assembled and (by now) is most likely operating at the Cadia underground mine in New South Wales, Australia, operated by Newcrest Mining. Vale will be watching developments here, where a three-month “pre-trial” cutting hard rock will take place.

Vale has laid out a testing plan for its own machine, with the unit set to cut around 400 m for the trial period.

IM had to find out more about this.

Fortunately Vale’s Luke Mahony, Head of Geology, Mine Engineering, Geotechnical and Technology & Innovation for the Global Base Metals Business; and Andy Charsley, Project Lead and Principal Mining Engineer, Technology & Innovation, were happy to talk.

IM: Why do you think industry collaboration is key in the underground hard-rock cutting space, in particular? Why has it been harder to develop and apply this technology in mining compared with other solutions such as automation, electrification and digitalisation?

LM: There are many various OEMs entering the market with hard-rock cutting equipment. All of them approach the problem a little bit differently, so it is difficult for one company to trial all of the options. At the same time, we are trying to leverage these new technologies and processes across the industry for a mechanical cutting type of future. For me, this is essential if we are to get the safety, cost and productivity benefits we need to make some of these new underground mines viable.

Comparing it to automation and electrification shows it is a ‘revolutionary’ concept as opposed to an ‘evolutionary’ one. Automation and electrification are more evolutionary concepts – automating an existing scoop or truck or electrifying it – whereas hard-rock cutting is more revolutionary and transformational in the sector, so industry collaboration is even more important.

IM: Since the project was presented at CMIC’s ReThinkMining Webinar, in June, have you had a lot more partnership interest in the project?

LM: We have seen a few other industry members ask questions and connect regarding this project. Some mining companies, while interested, are a little unsure of how they can get on-board with a project like this. What we have done is to utilise the CMIC consortium to make it the foundation of this collaboration, ensuring it is as easy and efficient as possible to join. Also, we want to cover the key concerns that mining companies have when it comes to collaboration, which CMIC is well aware of and can address.

CMIC is well connected with underground professionals and like-minded companies, and is able to pull in interest and facilitate the collaboration framework.

IM: What has happened to the MRE project timeline since June? Are you still on for receiving the machine in early 2021 to start testing later in the year?

AC: The machine has been assembled and we will mobilise it to Canada in early 2021. All of the underground cutting, in Canada, is scheduled to start in April 2021.

Komatsu have assembled two units – the first unit has come off the assembly line and is about to start trials at Cadia any day now. The second machine has just completed final assembly and will undergo Factory Acceptance Testing in the next few months, while we monitor the initial performance of the first machine. The second machine will come to Canada early next year and, if there are any modifications required, we can carry them out, prior to it going underground.

IM: How has the machine changed from the prototype that was initially deployed at Cadia and shown at MINExpo 2016?

AC: In 2016 and 2018, Komatsu implemented a proof of concept and, after that proof of concept, there was interest from miners to build a full commercial unit – which has happened now.

The prototype was ultimately to test the enabling cutting technology, whereby this element was retrofitted to a medium-sized roadheader for manoeuvrability. What Komatsu has done now is fully embed it into a system more like a continuous miner, which has the cutting arm, ground handling shovel & collector and the rest of the body to put it into a full production, continuous operation. It is now going to be part of the production process, as opposed to just testing the cutting aspect.

IM: Considering the end goal of this project is to evaluate the type and number of applications for which hard-rock cutting is suitable across industry (not just at Garson and the McConnell orebody), why did you select the Komatsu HRCM?

LM: It’s really about the Komatsu DynaCut Technology, which, for us, is an extremely low energy process for cutting the hard rock compared with, say, a TBM.

At the same time, what attracts us is the ability to integrate it with existing infrastructure within our current process at the mine – bolters, trucks, LHDs, etc. It is not about fully redesigning the mine to implement this technology.

This trial is that first step to really prove and understand the Komatsu DynaCut Technology in terms of dealing with cutting our relative hard rock in Sudbury. In that regard, the Komatsu technology provided the best technical opportunities for the conditions at hand.

IM: When the machine gets going in Australia, what hardness of rock will it be cutting in the hard-rock stage? How does this compare with Garson?

LM: Cadia is a rock ranging around 200 MPa, whereas in Sudbury we would be looking around 250 MPa. That’s when you talk about Uniaxial Compressive Strength (UCS) of the rock.

When you start looking at this undercutting technology, there are a few other aspects you need to consider. This includes rock toughness – the ability to resist a crack when a tensile force is applied, sort of like a jackhammer – and brittleness – how much energy that rock can absorb before it breaks.

Ultimately, we are working with Komatsu to understand how we should adapt an undercutting technology for our mines, and what the key parameters to consider are. At this stage, UCS seems to be the benchmark in the industry, but I think there will be a lot more considerations to come out of this project.

IM: What are the reasons for applying the technology at Garson? Were other areas in Sudbury considered?

AC: The priority for us was to have a shallow, low stress ground environment to start off with. At the same time, these are significant machines that would have to be disassembled if you were going down a shaft, which would be complicated. We have ramp access at Garson which makes things easier.

The other point is that Garson is an operating mine so we have got the facilities that can support the project; everything from removing the rock to ground support, service installation and surface infrastructure.

IM: How widespread do you think hard-rock cutting could be across the underground industry? Could it eventually become a mainstream method to compete with drill and blast?

LM: This is the ultimate question. I would like to say yes, it will become mainstream. It is our intention to really develop and prove that it can not only compete with drill and blast, but ultimately improve on it. This will see, in the future, an application for both mechanised hard-rock cutting and drill and blast.

You are going to need to look at fundamental KPIs such as safety, productivity and the cost associated with that productivity.

The focus now is to mature the cutting technology and start to develop the production or the process that goes with underground development beyond just cutting rock.

When developing around sensitive areas where you require low disturbance, hard-rock cutting will be important, as it will be in highly seismic ground. Then, if the unit cost of operating these machines gets low enough, you can start to assess orebodies that were previously not viable. At the same time, it is an electrified process so enables the industry to accelerate some of the decarbonisation plans for underground mining.

IM: Anything else to add on the subject?

LM: I think it’s fair to say, there will be no ‘one-size-fits-all’ solution when it comes to hard-rock cutting. Different OEMs are going to develop and mature solutions and there will be applications for each of them, but we have got a long way to go to really understand that as an industry.

The ultimate goal is to get that industry collaboration between OEMs and industry going to ensure solutions are developed that show a way forward for the sector.

This Q&A will feature in the annual continuous cutting and rapid development focus, soon to be published in the IM November-December 2020 issue. Photo courtesy of Komatsu Mining

MobileTronics trackless trains complete world first driverless TBM transport

MobileTronics, together with the joint venture partners STRABAG and Salini Impregilo, has successfully demonstrated the world’s first completely autonomous transportation of a tunnel boring machine (TBM) using trackless VirtuRail® trains.

The demonstration took place on the construction site ‘Ahrental’ of the Brenner Base Tunnel project, close to Innsbruck, Austria.

On this site, the supply of the TBM was realised by trackless trains. These rubber tyred, about 60-m long trains consist of five single cars and enable continuous transport from the loading area to the TBM, via a 2.5-km long access tunnel set at a decline of close to 12%.

MobileTronics says: “This innovative way of transport does not need the installation and maintenance of the steel rail network. At the same time, the roadways can be used for regular cars used by the underground staff.”

MobileTronics’ VirtuRail System steers all 18 axles electronically, allowing precision handling where all axles follow the first in line. An additional driver assistance system guides the first axle automatically in the tunnel and is also used for obstacle detection. This system can guide the train around a 90°curve on 30 m radius at the end of the access tunnel.

The docking of the train inside the TBM backup is also performed automatically; under regular operation, the driver only controls the speed.

Since May 2016, these trains have accumulated more than 200,000 km without a single significant issue, according to the company, adding that this technology played an important role in the TBM achieving an advance world record of 62 m over 24 hours on May 14, 2017.

To carry out the fully autonomous drive, the on-train electronics were supplemented by electronic ‘traffic signs’ in the tunnel. The train uses these to read its position and set the driving parameters for the next section.

Another successfully implemented challenge was the passing of oncoming traffic and the interaction with other vehicles driving in the access tunnel. This demonstration, prepared with STRABAG/Salini Impregilo, was carried out on December 3 and showed the full potential of autonomous operation in an environment not exclusively populated by autonomous vehicles, MobileTronics said. “Thereby, it has been proven that a fully driverless operation is possible using the VirtuRail technology.”

In the future, material logistics, especially on construction sites with several TBMs, can be remotely supervised from a central control room. “This makes VirtuRail an important future component to improve cost efficiency and safety of tunnelling operations,” MobileTronics said.

“Also, in mining, VirtuRail has the potential to improve underground transport: by performing the mass transport in a flexible way on the production level a separate transport level for rail bound mass transport may become obsolete.”

MobileTronics, together with its Polish sister company, MT-Silesia, in Wroclaw, specialise in electronic guidance and navigation of mobile equipment in safety critical environments.

Rio Tinto starts up TBM at Kemano Second Tunnel project in Canada

Rio Tinto, together with the Cheslatta Carrier and Haisla First Nations, has celebrated the launch of the tl’ughus tunnel boring machine, a key milestone towards completing the Kemano Second Tunnel project for the BC Works aluminium smelter in Kitimat, British Columbia.

The 1,300 t machine was named by the Cheslatta Carrier nation after a giant snake that, according to legend, once bored through the mountains and landscape around the nearby Nachako Reservoir.

It will dig 7.6 km of tunnel through a mountain as part of a C$600 million ($458 million) project to enhance the long-term security of a clean power supply for the BC Works smelter.

Rio Tinto Aluminium Managing Director Altantic Operations, Gervais Jacques said: “Launching the tl’ughus in partnership with the Cheslatta Carrier and Haisla First Nations is an important milestone for our world-class aluminium operations in British Columbia. Our smelter in Kitimat produces some of the world’s lowest carbon aluminium and this project will enhance the long-term security of its supply of clean, renewable hydropower.”

Construction of the Kemano Second Tunnel project is expected to be complete in 2020. It will supply the Kemano powerhouse with water from the Nachako Reservoir, creating a back up to the original tunnel built over 60 years ago.

Frontier Kemper Aecon has been selected as the main contractor for the project, with Hatch being the EPCM. Herrenknecht has supplied the TBM.

The project will see some 250,000 m³ of tunnel rock excavated by the tl’ughus, while 8.4 km of an existing portion of the second tunnel (excavated in the 1990s) will be refurbished.

Phase 1 of the project was completed in 2013 to coincide with the Kitimat Modernisation project and involved construction of interconnections to the existing portion of the second tunnel.

The Cheslatta Nation selected the name for the tunnel boring machine – tl’ughus – as it shares many parallels with the Kemano second tunnel project, according to Rio.

Kitimat produced 433,000 t of aluminium last year, up from 408,000 t in 2016 and 110,000 t in 2015.