Tag Archives: TBM


Anglo American lays out 5 Mt/y Woodsmith polyhalite plan ahead of full design review

This week, Anglo American hosted an investor and analyst day at its in-development Woodsmith project, in the UK, with several key technology takeaways cropping up from an in-depth presentation from Tom McCulley, CEO, Crop Nutrients.

In reviewing progress and the past, McCulley stated that Anglo has decided to start Woodsmith as a 5 Mt/y operation, with a staged ramp-up planned to the 13 Mt/y rate. The plan to sink 1,600 m production and service shafts, establish a mechanised mine, construct the 37-km-long underground tunnel and build a materials handling facility with priority access export facilities remain part of this. The potential to phase ventilation & production level development within the underground mine, potential to phase conveyor upgrades in the underground tunnel and the potential to carry out a phased expansion as required for the export facilities are all options for the 13 Mt/y blueprint.

This change has required some of the scope to go back to study phase – hence the reason why Anglo has been mooting detailed design reviews and non-critical path studies – looking at how to optimise investment and modularise the construction to get maximum value from each phase, McCulley said.

“I feel far more comfortable today about how we are setting up the project for the long-term success but managing in a capital efficient way,” McCulley said during his presentation.

Some of the elements keen observers have been watching at Woodsmith are related to mechanised underground development – both vertical (via shaft sinking) and horizontally (via tunnel boring machines (TBMs) for the 37-km-long tunnel).

TBM-led tunnel transformation

In terms of the latter, Anglo American is soon expecting to set a World Record for the longest TBM tunnel developed by a single TBM. This is currently set at 25.8 km, with the Woodsmith team having already reached the 25-km (25.3 km) mark.

“Beyond this we will pass our next intermediate shaft at Ladycross, where we will take a 3-4 month maintenance pause as we set up the TBM for the final push to 37 km, and we expect to reach the Woodsmith mine in late 2026,” McCulley said.

The machine used at Woodsmith is a Herrenknecht hard-rock TBM that, McCulley says, works similarly to the Shaft Boring Roadheaders (SBRs) being used for shaft sinking (more on that soon) in that it cuts the soils, without blasting, and the material is transported through the machine and out of the tunnel via a conveyor that is part of the TBM.

“In addition to excavating the material, the TBM also simultaneously lines the tunnel via pre-cast concrete segments (six segments make up a ring around the circumference of the tunnel); these concrete segments are fabricated at the Teesside port by a project dedicated facility,” McCulley said.

He said in every measure the tunnelling on the project to date has been an amazing success, aided by a solid team performance. This team is made up of contractors from Strabag, Herrenknecht and Anglo’s in-house personnel.

Progress has been aided by consistent ground conditions across the tunnel within what is called Mudstone strata, McCulley said.

“These conditions are very predictable and cutting is easy for the machine which minimises the bearing wear, which is a key risk area for the TBM,” he said. “This consistent strata has allowed us to switch our strategy from three TBMs to one TBM for the entire 37 km, which means we will not only pass the World Record, but we will also smash it when we reach Woodsmith in late 2026. This reduction in TBMs had a knock-on impact of saving significant capital over what was originally planned.”

Anglo is consistently seeing average rates increase to over 20 m/d and trending closer to 25 m/d, which compares favourably with about 16-17 m/d in late 2021.

Tom McCulley-Anglo American
Tom McCulley, CEO, Crop Nutrients

SBRs on the up

Mine development via TBMs is relatively proven when compared with the use of Herrenknecht SBRs for shaft sinking in mining, with Woodsmith representing only the third deployment of the technology in mining following Jansen (BHP) and Nezhinsky (Slavkaliy).

Anglo has two SBRs on site at Woodsmith, sinking the production and service shafts at the project. Redpath, which carried out the shaft sinking work at Nezhinsky, is steering developments at these two shafts, in addition to the material transport system shaft. Only the much deeper production and service shafts are being sunk via mechanised means with the SBRs.

Overseeing this and all developments at the operation is Worley as an engineering, procurement and construction management contractor.

Sinking of the service shaft began in September-October 2022, followed some six months later with activities at the production shaft. McCulley said these two were now around 550-m deep and 340-m deep, respectively.

“We typically see more daily meters from the production shaft due to the service shaft lessons being applied to the production shaft, so I’m excited as I think we may have a race to polyhalite!” he said. “We are very pleased with the progress made on both shafts since Redpath started sinking in 2022.”

On the advantages associated with using SBRs, McCulley said: “Some of the primary benefits of these machines is they are inherently safer than traditional sinking. They also eliminate the need for explosives, which is a huge benefit to us with the community as we don’t encounter noise complaints experienced in other mines. I expect these machines to be the future of shaft sinking. They are just safer, quicker and more predictable.”

The SBR is generally working in autonomous mode for most of the time following a program with pre-set parameters for cutting, according to McCulley, who said the company is expecting an average rate of 1 m/d in each shaft over the full 1,600-m length of the shafts.

“This 1 m/d includes all routine maintenance and what we call non-routine work, like installing water cubbies for pumping water out of the shafts, probe drilling, tubbing and grouting,” he said.

“Ultimately, this is the right machine for the job at Woodsmith and the cutting rates we achieve are 1.5-2 times what we would do with traditional methods.”

Looking at current sinking progress and plans to hit the orebody in 2027 in the service shaft (with the production shaft being six months behind that), McCulley pointed out a 250-m section of sinking in Sherwood Sandstone, which the company expects to reach next year.

“This 250 m of strata will see our rates reduced from our 1 m/d to something between 0.5 m and 0.75 m a day, and this will impact us for most of next year and early 2025,” McCulley said. “Once through that strata, we do not expect any further issues with the ground conditions significantly impacting production.”

The Sherwood Sandstone is characterised as a strata of highly competent rock, about 120 Mpa, according to McCulley, which is at the top end of the SBR rock hardness capacity given by Herrenknecht.

In addition to the hardness, this strata has the potential for some water fissures (ie cracks in the rock with high pressure water), according to McCulley.

“The good news for us is we hit a 2.5-m layer of this material a few weeks ago and we learned from this that we need to make some adjustments to our cutter heads and cutting picks, and now we are far more prepared than we would have been otherwise,” he said. “We are also prepared with alternative plans, including potential use of lasers, plasma blasting and/or microwaves if needed, but we expect our updated cutter head and next generation picks, developed by Element 6 of De Beers, will cut through the rock at the rates I previously mentioned. In addition, to the hard rock, this strata has a risk of high-water flows in small sections of the strata so we will need to seal the shaft via grout from the shaft. This means as we come across water, we will inject chemical grout into the fractures to block water bearing cavities and control water inflow.”

Adding to McCulley’s confidence is the fact that the nearby Boulby mine encountered the same strata some time ago, which that team progressed through via the same exact grouting technique Woodsmith is planning today.

In terms of priorities for 2023, McCulley said the team expected the service shaft to be between 650-700 m at the end of the year, versus the current circa-550 metres today, whereas the production shaft could reach 450 m by this point.

“Both shafts, if they hit the numbers noted will exceed our planned targets for the year,” he said.

“The MTS shaft and Ladycross shafts are both sunk, and we are working to fit them out during the remainder of the year. In the tunnel we have driven 4.3 km this year, we are at 25.3 km and we expect to reach 27 km, which is our stretch target for the year.”

For 2024, while Anglo continues to work through the studies, it doesn’t see any changes to its plans right now and still expects to be around the $1 billon capex number for the next few years.

McCulley added: “Our vision at Woodsmith with regards to technology is to ultimately develop a peopleless underground mine, where operations and maintenance are all controlled from the surface. This is a journey, but many technologies are already out there, we just need to put the system in place and the wherewithal to help the vendors take the next step. This will not happen from the start, but with our vision and with the team we have in place, I have no doubt that in the future this vision will become a reality.”

When at full production, Woodsmith will be a FutureSmart Mine with all the modern technologies, according to McCulley, with these characteristics ensuring the company has a low cost, high volume mine for many years to come. Continuous miners are expected to be used in a room & pillar mining application, combined with mine cars, shuttle cars or conveyors.

“On top of the mining/processing technology, I see some interesting parallels with the farming industry. They are rapidly adopting technologies, and we are very well placed to support this transition in areas like sensing, scanning, AI, etc. I think with our Anglo American Woodsmith project experience in technology we are uniquely positioned to help support this transition in farming and this is something that will have added value to our product for years to come.”

Robbins accelerates Fresnillo development with MDM rectangular tunnel boring machine

At Fresnillo, a silver mine in Mexico, Robbins and the mine operator are making good headway on accessing a deep underground orebody using a rectangular tunnel boring machine.

Known as the MDM5000 (standing for Mine Development Machine), the TBM has dimensions of 5 m x 4.5 m and is capable of excavating a flat tunnel invert for immediate use by rubber-tyred vehicles, Robbins says.

The successful operation is the result of extensive discussions between tunnel boring machine (TBM) and mining equipment manufacturer, Robbins, who designed and supplied the machine, with TOPO Machinery and Fresnillo plc.

Fidel Morin, Projects Superintendent for Fresnillo Mine, said: “We decided to work with Robbins for their experience. A lot of people have tried to provide these kinds of machines, but nobody has done it. Robbins used their experience and their skills to provide us with a rectangular profile machine.”

With more than 1,700 m of advance thus far at rates up to 52 m in one week and 191 m in one month, the MDM is significantly faster than drill and blast excavation, Robbins claims. The MDM is excavating in andesites and shales with quartz intrusions that have defeated earlier attempts to excavate these tunnels with heavy roadheaders, according to the company.

A crew member operates the MDM5000 in Fresnillo, Mexico from an  air-conditioned control cabin using touch screen technology

“We’re making history,” Morin said. “Fresnillo is always looking for new technology, and we believe that the usage of the MDM5000 is going to be something extremely successful, not only for our company but also for the mining industry.”

While the MDM5000 has proven itself in underground mining, Robbins sees it as just one component of a new 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 the orebody and transport material. The unique TBMs would be lighter, more mobile and able to bore inclines, according to the company.

“It’s all about reaching first ore quicker, and then economically mining the orebody while reducing tailings,” Robbins President, Lok Home, said of the strategy. “Mechanised tunnelling machines have the potential to revolutionise the underground mining industry.”

Robbins’ new solutions for underground mining are the latest in a legacy of innovations the company has developed over the years.

“Introduced equipment ranges from raise drills to non-circular mobile miners to continuous conveyors and customised TBMs at projects including the Grosvenor Mine in Australia, the Stillwater Mine in Montana, USA, and others,” the company said.

As for the MDM5000, the machine has undergone major component enhancements during the course of its successful bore at Fresnillo mine. It was first transported to the -695 m level of the mine and underwent final assembly and launch in a cavern, where sections of the MDM were moved by crawlers and pieces were lifted by hoist. The machine is now boring a 270° spiral to end above the original tunnel. It will then be backed up to the original tunnel and continue driving straight ahead.

MDM tunnelling has advance rates roughly twice those of a drill and blast heading, and results in smooth tunnel walls, less overbreak and minimised ground support, according to Robbins (credit: Fresnillo plc)

Fresnillo previously said it was using the Robbins TBM to develop the new San Alberto orebody at the underground mine, with plans to carry out 11 km of development in total for that project.

Developed for use in underground mining in rock up to 200 MPa UCS, the MDM5000 is particularly useful for long access tunnels and development drifts, Robbins says. Using disc cutter technology proven on traditional, circular TBMs, the MDM5000 excavates with a reciprocating cutterhead and swinging cutterhead motion to create a rectangular cross section tunnel.

“The MDM offers a number of advantages for mines over other methods including drill and blast,” Robbins says. “MDM tunnelling has advance rates roughly twice those of a drill and blast heading, and results in smooth tunnel walls, less overbreak and minimised ground support. The increased advance rates 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.”

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

Driverless tunnel boring machine transport just the start for MobileTronics and VirtuRail

Building on a world first demonstration of fully autonomous transportation of a tunnel boring machine (TBM) using trackless VirtuRail® trains at the Brenner Base Tunnel project, in Austria, in December, MobileTronics is setting new goals.

The demonstration took place on the construction site ‘Ahrental’ of the STRABAG and Salini Impregilo-owned project, near Innsbruck, with the supply of the TBM 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’ 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.

As MobileTronics’ Christoph Mueller and George Biro said, this autonomous operation did not take place in a closed special purpose area; all tests, as well as the showcase, took place in the regular working environment of the tunnelling construction site.

Mueller and Biro said: “Extending the existing application to a fully autonomous system working safely in the tunnelling environment, from the technical point of view, would not require more than three to four months.

“The main effort would be to install a central supervision workplace, which provides a central overview of the locations and status of the trains together with live video and the possibility for the remote operator to restart and manually manoeuvre in exceptional situations.”

For future autonomous operation, the availability of a mechanical vehicle originally intended for fully autonomous operation, “with an optimised technical reliability of the underlying mechanic and hydraulic systems would be required”, according to Mueller and Biro.

The company is also looking at completing a fully-electric operation as it looks to reduce emissions and boost environmental credentials. “This would also save significant cost for tunnel ventilation compared to diesel-operated machines,” the company said, adding that the electric vehicles were also likely to provide lower operating costs due to higher energy efficiency.

“In the following projects, MobileTronics already has gained extensive experience in integration of battery- and hybrid-powered electric vehicles as well as in integration and configuration of the high voltage electric components including motors and frequency converters,” Mueller and Biro said.

“The future VirtuRail trains, therefore, will be modular products made of reliable components designed for fully-autonomous operation, however with the option of manual operation from two cabins or only one driver cabin.”

The applications for VirtuRail are not limited to TBM supply operations, with the trains potentially being used in mining for raw material transport: “In underground mines, for example, the use of rubber-tyred trains has the potential to replace dedicated train transport levels which will speed up the mining operations as the separate transport level does not need to be excavated before mass mining starts,” Mueller and Biro said.

They continued: “Also in surface mining, VirtuRail trains have the potential to become an alternative to conveyor belt installations or traditional truck transport.”

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.

Master Drilling aims for new status as mining TBM specialist

Master Drilling, through subsidiary Master Tunnelling, is not trying to re-invent the wheel with its mobile tunnel borer (MTB) concept, but that doesn’t mean to say the application of such technology will not have a big impact on the underground mining space.

The company, up until recently thought of as a raiseboring specialist, is up against stiff competition in the horizontal mechanised cutting sector. It has Epiroc and its Mobile Miner, Sandvik and the MX650, Caterpillar and the RH55 and Komatsu (Joy) and its DynaMiner to contend with, all of which have been trialled in underground mines.

But, the South Africa-based company is hoping its contracting model, tunnelling partner, modular design and operational flexibility will put its MTB in the lead.

Mining companies on a global basis have been looking for a mechanised, continuous alternative to the labour intensive drill and blast batch process for decades.

Several companies have tried to cater to this need, but no one technology has provided the ‘silver bullet’ as of yet.

Still, the drive to get personnel out from harm’s way, the need to improve tunnelling quality with an increasing number of block cave developments and decrease the payback period for what can sometimes be multi-billion dollar investments has resulted in the latest slate of horizontal cutting machines.

Master Tunnelling has partnered with Italy-based tunnelling expert Seli Technologies to launch its new product and IM recently visited a quarry site just outside of Rome where the first MTB is being assembled and tested.

On site, Koos Jordaan, Executive Director of Master Drilling, talked IM and a host of other interested visitors from mining companies through the machine specifics.

“To reduce risk, we stuck to proven cutting technology,” Jordaan said, pointing to the cutter head design in a schematic within one of the quarry’s temporary offices. “The concept is not so radical, it is more incremental based on tunnel boring.”

The full-face cutter head is made up of 17” disc cutters, which are conventional from a TBM perspective, but are made up of five separate segments. This cutter head, like the majority of the 240-300 t MTB, is designed to be broken down for transport.

The MTB is made up of four track-mounted units containing various parts – the cutter head and bolting section is up front, followed by the transformer and 300 m capacity water and electrical reels on the third unit, and a 14 m3 capacity storage bunker and discharge system on the fourth unit.

The units are also equipped with conveyors that transport the mucked material along the machine.

These can be individually broken down and potentially shipped in 10-12 20-foot containers, according to Jordaan.

This modularity should enable Master Tunnelling to access existing mines with decline infrastructure and to start tunnelling from an underground location, as well as to work on such infrastructure from the surface.

The full-face cutter head is capable of a 1 m advance stroke and can cut rock in excess of 300 MPa compressive strength. It can also be remotely controlled by an operator, reducing exposure to the face.

The MTB comes with 5.5 m diameter cutter head or 4.5 m diameter cutter head. The former is for declines, portals, haulages, inclines, ramps, ring roads, etc, with the latter allowing for excavation of drives and contact tunnels.

Master Tunnelling is aiming for an advance rate of 6-9 m/d in 200-250 MPa rock, but is not discounting the possibility of a higher rate should the additional mucking transport systems behind the 23 m (4.5 m diameter MTB) or 31 m (5.5 diameter MTB) machines be able to keep up.

Jordaan admits going past the 300 MPa threshold was likely to lead to advance rates dropping off by as much as a third, but is adamant the machine has the capability to cut through such rock.

All of this cutting takes substantial amounts of power, which the four hydraulic motors have in abundance. The MTB has 1,300 kW of installed power and a 1,600 kVA on-board transformer that more than covers the machine’s requirements.

Behind the cutter head, hydraulically-powered side grippers ensure the machine can thrust forward and start cutting, while there is a finger shield that both protects workers and allows for a support drill to install cable bolts for ground support.

Master Tunnelling envisages at least three personnel being required for full continuous operation in most setups.

Driving on a flat roadway

As Master Tunnelling points out, “a round profile tunnel is not ideally suited for vehicles that require a flat driving surface, such as most trackless mining equipment.”

This is where a articulating tail conveyor at the end of the fourth tracked unit – containing the 14 m3 storage bunker – evenly distributes 3-5% of the cut material. This should provide the sort of flat driving surface trucks will need to come in and pick up the material.

Master Tunnelling has some form here, too. Its Master Drilling parent company carried out a horizontal raisebore drive of 180 m length and 4.5 m diameter in a kimberlite pipe at Petra Diamonds’ Cullinan mine in South Africa recently. A flat driving surface was created by using a similar solution to the one the company has devised for the MTB.

There are also a few other features worth flagging.

The MTB is able to operate on a 12° incline/decline, has a 30 m turning radius and can be dismantled and brought back to surface after a project is complete.

The latter is different from the bulk of conventional TBMs where, after use, they are buried underground never to be used again.

Master Tunnelling is also taking safety seriously with the MTB. Not only is it shielding bolting operators from potentially hazardous situations above their heads all the way from the cutting face, it is also installing gas detection, proximity detection and fire suppression systems on the units. An operational monitoring system, meanwhile, ensures the full-face cutter head is advancing as planned and the accompanying units are tracking as they should be.

Master Tunnelling anticipates a four-hour maintenance period for the MTBs every 24 hours based on a three, eight-hour shift pattern. During this time, the disc cutters can be replaced and the dust suppression and collection system can be checked.

The company also envisages this time being used for drilling a 30-50 m probe hole in advance of the MTB. This would be drilled through an opening in the cutter head and provide integral information about the water and gas levels of the approaching rock.

The MTB doesn’t do away with drilling and blasting altogether. To initiate cutting, the machine requires a rounded profile side wall to grip and thrust to take it forward. This requires a starter frame to be installed in advance of the drive, which can be put in position with a 15 t capacity wheel loader with appropriate manipulator attachment.

The frame requires a starting chamber 6.5 m high, 8 m wide and 12 m deep excavated by conventional drilling, blasting and scaling.

In an undercut level for block caving, this preliminary batch phase would only form a “small part of the excavation required”, Master Tunnelling says.

In addition to considering the setup requirements for the MTB to start operation, it is also worthwhile to look at what will follow the machine in terms of loading and hauling the excavated material.

This is where the bunker backup unit positioned at the end of the four tracked units proves useful, acting as a storage facility to allow truck changeover to take place behind the MTB when one truck is fully loaded and another truck comes in. This allows for continuous operation of the MTB incorporating a batch haulage system.

On long, straight advances there is also the possibility of using mobile conveyors for haulage, however the company thinks there will be less of these applications given the MTB’s major strengths are developing tunnels with a curvature or on a decline/incline.

Contractor advantages

In the battle for a market leading, horizontal, mechanised cutting technology, Master Tunnelling has a few advantages over its much bigger rivals in the mining space.

One: it is a contractor, meaning it is not asking customers to invest in this capital-intensive equipment. Instead, it will be contracted by the client to provide the MTB and associated equipment required for logistics and material handling.

Two: It has a partner in Seli Technologies that has carried out more than 1,000 km of tunnelling excavations and has been involved in mining work before (it excavated an 8 km long, 4.2 m diameter tunnel for Anglo American at Los Bronces, in Chile, back in 2009).

Three: It is offering something that is modular, can be broken down and assembled underground, and can be relocated from one project to the next.

Also, Master Tunnelling is offering the ability to turn around corners and keep tunnelling with the MTB, which could be particularly useful when tracking complex, or faulting mineralisation. It could also come in handy should the MTB encounter particularly hard to bore rock.

The concept phase of the MTB only started in April 2017 and only one MTB has so far been manufactured. So, for the right partner, there is the chance to get in early and to advise on their customised requirements.

Master Tunnelling is clearly thinking to the future in this regard, with the bulk of the MTB hardware being ‘automation-ready’.

Even though the set up at the quarry in Italy is to test basic functionality – cutting 10-20 MPa rock for 50 m and carrying out a 30 m turn – it has provided interested parties a chance to consider what the machine could do for their own operations.

Once it has optimised the setup time and demonstrated what it can do in some fairly competent rock underground, the wider mining community may start to further appreciate the MTB and what Master Tunnelling is offering.