Tag Archives: Shaft sinking

Caledonia Mining heads for Central Shaft commissioning at Blanket gold mine

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Caledonia Mining says it has fully equipped the Central Shaft from its base to the surface collar at the Blanket gold mine in Zimbabwe, with commissioning on track for the March quarter of 2021.

This milestone has been completed considerably below budget and within a time frame to underpin the company’s expectation of delivering production of 80,000 oz of gold in 2022, it said.

The Central Shaft project, which extends Blanket’s life of mine to the current time horizon of 2034, was initially slated to reach a depth of 1,089 m, however, was extended to 1,204 m.

Steve Curtis, Caledonia Chief Executive Officer, said: “Shaft sinking is widely regarded as one of the most dangerous activities in mining and I am proud to report that over more than five years the crew achieved 1,850 fatality free shifts to date with only two loss time injuries (LTI) and achieving more than one million LTI-free man hours worked since the last LTI.”

He added: “Central Shaft is one of the largest gold mining investment projects in Zimbabwe and will be transformational to our business: our target production is set to increase by 45% to 80,000 oz by 2022 while our long-term all-in sustaining costs are expected to drop to $700-$800/oz. Central Shaft will also position us to step-up our deep level exploration which, if successful, may extend Blanket’s life of mine, which is currently to 2034.”

The capital cost of the project to date is around $60 million, compared with initial sinking contractor quotes received of about $100 million. The shaft work was completed by Blanket crews with supervision from Sinking Engineering Mining Construction, Caledonia said.

BHP commits another $272 million for shaft lining at Jansen potash project

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BHP has agreed to invest another $272 million in the Jansen Stage 1 potash project in Saskatchewan, Canada, following challenges encountered with placement of the shaft lining and more recent impacts from the company’s COVID-19 response plan.

Up until this point, BHP had committed to spending $2.7 billion on the project.

BHP said in its September quarter results: “As a consequence of the challenges encountered earlier with placement of the shaft lining and then the more recent impacts from our COVID-19 response plan, the board has approved additional funding of $272 million for the completion of the shafts, resulting in a total budget of $3.0 billion (previously $2.7 billion).”

This is expected to result in the excavation and lining of the 7.3 m diameter production (975 m deep) and service (1,005 m deep) shafts – sunk by DMC Mining using Herrenknecht’s Shaft Boring Roadheader – and the installation of essential surface infrastructure and utilities.

Back in August, the company said it would not decide on an investment in the full Stage 1 project until mid-2021, a delay on the February 2021 deadline it previously advised of. This was down to the shaft lining problem.

The current Stage 1 plan, which is 86% complete and has an expected capital outlay of $5.3-5.7 billion, involves building out initial capacity of 4.3-4.5 Mt/y of potash, with expansion optionality.

BHP added: “Jansen Stage 1 remains well positioned with attractive medium to longer-term commodity fundamentals, and is set to be a high-margin, low-cost, long-life asset, with multiple, basin-wide, expansion opportunities. As always, we will be disciplined about our entry into the market and it must pass our strict Capital Allocation Framework tests.”

M&R Cementation ready to make shaft sinking transition at Palabora copper mine

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The sinking of the 1,200-m deep ventilation shaft at Palabora Copper, in South Africa, is proceeding apace, notwithstanding the COVID-19 shutdown and restrictions, contractor Murray & Roberts Cementation reports.

Work began on the 8.5 m diameter shaft early in 2019, with pre-sinking recently reaching a depth of 50 m and the changeover from pre-sink to main sink almost complete, according to Murray & Roberts Cementation Project Executive Mine Development, Graham Chamberlain.

Part of the development of Palabora Copper’s new LIFT II underground block cave mining area, the shaft will be developed to a final blind sink depth of 1,190 m, with a drop raise to its final depth. Completion is expected in the September quarter of 2022, Murray & Roberts Cementation says.

“We were required by the client and national lockdown regulations to pause our work schedule, but operations resumed as planned when restrictions were relaxed,” Chamberlain said. “The priority is to ensure that safe working conditions are maintained, and the COVID-19 infections are avoided.”

The project is using automated machinery at the shaft bottom, removing employees from high-risk contact areas. Modern, high-penetration rate hydraulic drills are deployed on robotic arms nested on the shaft sinking stage. This allows operators to conduct drilling at any position in the shaft without physically being in contact with the drills, the company says.

“We shorten our cycle times with the use of explosive delivery pods containing sensitised emulsion,” Chamberlain said. “Electronic systems deliver real-time data on blast holes numbers, volumes and pressures, improving blasting efficiency and quality.”

To reduce potential disruption from the intersection of poor ground conditions, Murray & Roberts Cementation takes the shaft lining to the bottom of the shaft during sinking. In the past, industry practice tended to carry this lining to about 20 m from the bottom.

“Our lining approach is applied with the use of a modified version of the traditional shuttering, and our specialised concrete mixes which we design for this specific purpose,” Chamberlain explained. “The mixes are prepared and delivered by our on-site batch plant.”

Chamberlain adds that the company’s focus on Zero Harm and a rigorous safety regime continues to deliver a high level of safety on the project.

Ivanhoe advances Platreef development studies after Moolmans completes sinking

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Ivanhoe Mines has announced another milestone at the Platreef platinum group metals project in South Africa, with construction complete at the 996-m level station of Shaft 1.

The achievement, completed well ahead of the contractual schedule, according to Ivanhoe, positions the company to equip Platreef’s initial production shaft, if it chooses to proceed with phased development of the mine on the Northern Limb of South Africa’s Bushveld Complex.

Sinking was carried out by contractor Moolmans, with the project remaining ‘Fall-of-Ground’ incident free since shaft sinking operations began in July 2016, the company said. On top of this, in June 2020, Moolmans and the Platreef team achieved South Africa shaft sinking industry leader status in terms of safety performance, according to Ivanhoe, which owns 64% of the project through Ivanplats.

Ivanhoe’s Co-Chairmen, Robert Friedland and Yufeng “Miles” Sun, said: “Given the flurry of recent transactions in precious metals markets, we are actively exploring a number of options that can help us unlock Platreef’s extraordinary value for the benefit of all Ivanhoe stakeholders.

“After all, Platreef is among this planet’s largest precious metals deposits.”

Platreef now has a completed shaft within a few hundred metres of the initial high-grade mining zone, according to Friedland and Sun.

“We have a mining licence, we have water and we have a team of highly-skilled employees,” they said. “The deposit has enormous quantities of palladium, platinum, rhodium, nickel and copper; and it has more ounces of gold than many leading gold mines.”

They concluded: “Given the current precious metals environment, I am confident that the pending studies will showcase the exceptional economics that one would expect from such a thick, high-grade and flat-lying deposit.”

Ivanhoe is updating the Platreef project’s 2017 definitive feasibility study (DFS) to account for development schedule advancement since 2017 when the DFS was completed, as well as updated costs and refreshed metal prices and foreign exchange assumptions.

The DFS for Platreef covered the first phase of production at an initial mining rate of 4 Mt/y, estimating Platreef’s initial average annual production rate would be 476,000 oz of platinum, palladium, rhodium and gold, plus 21 MIb (9,525 t) of nickel and 13 MIb (5,897 t) of copper.

Concurrently, Ivanhoe is finalising a preliminary economic assessment for the phased development production plan for Platreef. The plan targets significantly lower initial capital to accelerate first production by using Shaft 1 as the mine’s initial production shaft, followed by expansions to the production rate as outlined in the 2017 DFS, Ivanhoe said.

“The re-evaluation is being done in parallel with the ongoing mine development work to access the thick, high-grade, flat-lying Flatreef deposit that was discovered in 2010 and outlined in the Platreef 2017 feasibility study,” it said.

The new auxiliary winder for the 7.25 m diameter Shaft 1, which is scheduled to be delivered to Platreef later this year, will be used to assist in equipping the shaft; and thereafter for logistics, shaft examination and auxiliary functions. The auxiliary winder will provide a second means of ingress and egress from the shaft after removal of the stage winder.

Shaft 1 is around 350 m away from a high-grade area of the Flatreef orebody, planned for bulk-scale, mechanised mining.

Alamos’ Island III goes on sinking mission for more gold

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Having weighed five scenarios for a Phase III expansion at the Island gold mine, in Ontario, Canada, Alamos Gold is proceeding with a plan to carry out a blind sink down to the 1,373 m level, build a paste plant, and expand the mill and tailings facility at the operation to boost production.

The company is no stranger to shaft sinking; its Young-Davidson mine, also in Ontario, has just had its Northgate shaft commissioned after Cementation used large diameter raiseboring technology to establish it as part of an engineer, procure and construct contract.

Yet, the shaft sinking route was not a foregone conclusion, with three of the five scenarios involving ramp haulage.

The Phase III Expansion Study, carried out with assistance from Hatch, Cementation, Airfinders, Golder, Halyard, SRK and DRC Estimating, looked at these scenarios using Deswik planning software to find further growth at the mine.

Having added 900,000 oz of the yellow metal to its reserve base already this year and hit a rate of 1,240 t/d in the March quarter (ahead of the nameplate 1,200 t/d rate), the company was keen to leverage these ounces at the same time as come up with a sound economic proposition for expanding and extending the mine.

Of the five scenarios, three involved ramp haulage (two retaining the 1,200 t/d capacity and one at 1,600 t/d) and two would see a shaft installed (at 1,600 t/d or 2,000 t/d). All apart from one option included the addition of a paste plant.

The company settled on expanding throughput to 2,000 t/d, from 1,200 t/d, through a shaft and paste plant build, explaining that this option presented the best economics.

As a result, the Phase III expansion will involve an initial blind sink down to 1,373 m, that new paste plant, and an expansion of the mill and tailings facility.

These investments, which would see the mine life double to 16 years from the eight years currently outlined in the reserve base, are covered in the total capital of $1.07 billion, which the company says is offset by the lower sustaining capital and operating costs of this scenario versus all that were evaluated.

Following the completion of the shaft construction in 2025, it is envisaged the operation will transition from trucking ore and waste to skipping ore and waste to surface through the new shaft infrastructure.

Output would rise to 236,000 oz/y starting in 2025, 72% higher than the mid-point of previously issued guidance for the mine in 2020, while mine-site all-in sustaining costs would fall to $534/oz, a 30% drop on the 2020 guidance.

Combined, this made for an after-tax net present value (NPV) of $1.02 billion at a 5% discount rate, and an after-tax internal rate of return of 17%, using a base case gold price assumption of $1,450/oz.

“These are also the lowest costs of any scenario evaluated reflecting the significant productivity improvements, decreased ventilation requirements, increased automation, and higher throughput rates associated with the shaft,” the company said.

While the company did not spell out what automation elements would be included in this expansion, on a webcast discussing the results, Chris Bostwick, VP, Technical Services, included details of an LTE network underground installation at Island as one continuous improvement project for 2020.

An Alamos Gold spokesperson later confirmed to IM that the LTE network was in the process of being installed with the project expected to be completed by the end of this year. “The network is primarily being installed for voice communications and real-time data gathering,” the spokesperson said.

Asked whether it was a pre-cursor to the use of autonomous haulage at the operation ahead of the expansion, the spokesperson replied: “We don’t have any firm plans for increased automation of our mobile equipment currently, but are actively monitoring the progress with the technology and this remains a potential down the road.”

With regards to automation within the expanded mine scenario, the only aspect currently being considered is the automation or tele-remote operation of the rock breakers and skipping, the spokesperson confirmed.

“Some of the trucking requirements could be automated down the road as noted above,” the spokesperson said. “The shaft expansion will make the entire operation more automated and productive.”

John A McCluskey, President and Chief Executive Officer of Alamos Gold, reviewing the study, said Island Gold had proven to be a “tremendous acquisition” for Alamos.

“We acquired Island Gold in 2017 at a cost of approximately $600 million when it had 1.8 Moz of mineral reserves and resources,” he said. “This high-grade deposit has more than doubled to 3.7 Moz and we expect further growth yet.”

While the planned expansion would make Island more profitable through increased production and lower costs, it would also “best position the operation to benefit from additional exploration success”, he said.

Long-hole open stoping will continue to be utilised as the primary mining method at Island, however, increased development and key infrastructure changes including the addition of a paste plant and shaft will allow for mining rates to increase to 2,000 t/d, it said.

The addition of paste fill underground will allow for faster stope cycling, thereby supporting higher mining rates and providing increased geotechnical stability, according to Alamos. It will also increase mining recovery, resulting in an additional 100,000 oz of gold recovered over the life of mine (from existing pillars). This represented an in-situ value of $145 million at a gold price of $1,450/oz.

The paste plant will have a capacity of 2,000 t/d and capital cost of $34 million with the plant expected to be completed in the December quarter of 2023, Alamos said.

When it comes to the shaft options, which Alamos Gold evaluated with the help of Cementation, it was decided that a conventional blind sink methodology would be used to provide “improved schedule reliability with minimal impact on existing operations”.

A combined raisebore from the 840 m level, and blind sink option below the 840 m level was evaluated, however, this option would significantly impact existing operations, Alamos said. “The cuttings from the raisebore in the upper mine, and waste generated from the conventional sink in the lower mine, would displace underground throughput capacity and significantly reduce mining rates below 1,200 t/d by as much as 400 t/d over the next several years,” it said.

The settled-on option will see a 5 m diameter concrete-lined shaft constructed with a steel head frame. The shaft will house two 12 t skips in dedicated compartments for ore and waste movement and a double-deck service cage for the transport of personnel and materials.

The company estimated an overall shaft sinking rate of around 9.6 ft (2.9 m)/d, which included a ramp-up period.

While the shaft will be sunk to an initial depth of 1,373 m, the hoisting plant will be designed for an ultimate depth of 2,000 m providing flexibility to accommodate future exploration success, the company said.

At the initial depth of 1,373 m, the shaft has a capacity of 4,500 t/d, more than sufficient to accommodate the peak mining rates of 3,300 t/d (ore and waste), according to Alamos.

The underground ore and waste handling and loading pocket will be a conventional configuration like that of Young-Davidson, the company said.

Once skipped to surface, ore will be trucked to the expanded mill circuit.

On top of the payback being sweeter for the shaft expansion, ventilation requirements are also lower than under the ramp scenarios given the significantly smaller mobile fleet, Alamos said. This allows the shaft to serve as the only new required fresh air source.

The total construction capital for the shaft installation including all supporting infrastructure is anticipated to be $232 million.

Further, 56% of tailings will be placed underground reducing tailings dam raise requirements, a capital saving of $13 million, according to Alamos.

The mining rate ramp-up to 2,000 t/d after the shaft expansion will be supported by a total of five 42 t haul trucks. This compares with a peak of 18 haul trucks required to sustain ramp haulage at 1,200 t/d and 25 haul trucks for ramp haulage at 1,600 t/d, the company said.

“This contributes to the lower ventilation requirements with the shaft expansion, and significantly lower diesel usage and greenhouse gas emissions,” the company said.

The mill expansion will include upgrading the crushing circuit, adding a second parallel ball mill, and a new elution and carbon in pulp (CIP) circuit with carbon screens. The total cost of the mill expansion is expected to be around $40 million.

The flowsheet of the new circuit includes upgrades and expansions for the following major process operations:

  • New vibratory grizzly feeder;
  • New primary crusher;
  • New fine ore stockpile and conveyors;
  • Additional primary ball mill;
  • Primary ball mill screen for both ball mill circuits;
  • Existing thickener converted to high rate thickener;
  • Two additional leach tanks;
  • New elution plant and kiln (ADR); and
  • Tailing pumps.

Mill recoveries are expected to average 96.5% over the life of mine, consistent with the historical performance of the existing operation, it said.

To accommodate the increased electricity requirements with the larger mill and shaft, the power line to site will be upgraded at a cost of $14 million, it added.

Despite the backfill options with the envisaged paste plant, an expansion of the existing tailings impoundment area is underway and required under all scenarios to accommodate the growth in the deposit over the last several years, Alamos said.

“With two planned future raises beyond 2020 and the addition of the paste plant, the tailings facility has sufficient capacity to accommodate existing mineral reserves and resources,” it added.

Alamos Gold to hit new highs after reaching new depth at Young-Davidson

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Alamos Gold says it has completed the lower mine expansion at Young-Davidson, in Ontario, Canada, with the successful commissioning of the Northgate shaft.

The lower mine expansion project was designed to boost underground production at Young-Davidson from 6,000 t/d to 8,000 t/d as the existing mid-mine infrastructure was replaced with the new lower mine infrastructure.

The project involved Cementation using large diameter raiseboring technology to establish the new shaft at Young-Davidson as part of an engineer, procure and construct contract.

Alamos Gold says the newly constructed lower mine infrastructure is larger, highly automated and more productive, with the transition expected to drive gold production higher and costs lower starting in the second half of 2020.

John A McCluskey, President and Chief Executive Officer of Alamos Gold, said: “This marks a significant milestone for Young-Davidson and turning point for Alamos as we transition from a reinvestment phase to a period of strong free cash flow growth.

“I would like to congratulate the entire team at Young-Davidson for this historic achievement, which will unlock the full potential of the operation. With a 13-year mineral reserve life, large resource base, and significant exploration potential, Young-Davidson is well positioned to deliver solid free cash flow over the long term.”

In addition to the Northgate shaft (pictured), the underground crusher and conveyor system have also been successfully commissioned, Alamos Gold said. Mining rates are expected to ramp up through the second half of the year to 7,500 t/d by the end of 2020.

The mine produced 188,000 oz of gold in 2019 at mine site all-in sustaining costs of $1,047/oz, Alamos said.

Cementation Canada ready to inject innovation into the underground mining space

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Injection Hoisting first came to the attention of the global mining audience after Cementation Canada, the technology developers, took the top prize along with KORE Geosystems at the DisruptMining event in 2017. Back then, the concept was viewed as a potential alternative to the labour- and cost-intensive process of shaft sinking.

More than three years later, the concept has developed along with the list of potential applications. This has Cementation Canada, a pioneer in the shaft sinking market, and the man in charge of injection hoisting developments, Alun Price Jones, looking at a much wider underground market for the innovation.

The process as envisaged by Cementation Canada starts with material (ore/waste) being transported to an underground crusher and reduced to <52 mm (2 in). After this, the material is weighed and transported to a hopper, which feeds the raw material directly into a slurry mixture. This mixture is continuously fed through the injection pump and looped piping system before being injected into the flow of carrier fluid by the injector.

Ore/waste rock material is transported in a riser pipe to the surface where solid materials (ore/waste) are separated, with the former transported to the mill for further processing. The by-product fluids, meanwhile, are separated, filtered and recycled.

With the company having recently been awarded C$88,355 ($62,948) of funding from the Northern Ontario Heritage Fund Corporation (NOHFC), IM thought it was the perfect time to get an update from Price Jones.

IM: What will the funding from the NOHFC provide the company in terms of furthering its ambitions with the injection hoisting system?

APJ: Injection Hoisting (IH) offers a unique opportunity for mine operators to consider an alternative to traditional mine hoisting or trucking. The purpose of this funding is to assist Northern Ontario businesses to undertake applied research or pre-commercialisation activities required to further develop new technologies and move them to market. Our grant will be put towards patent costs, basic internal engineering costs, and peer review. The next step is to build a full-scale prototype, and Cementation is now looking to build a working installation in collaboration with mining companies.

IM: Since the IH system was introduced at DisruptMining, how has the concept/technology developed?

APJ: The concepts have been further developed, and the basic engineering advanced sufficiently for it to have been subject to formal peer review, completed by Patterson and Cooke who have worldwide experience in design of material transport systems by pipeline. The review gave a most favourable outlook on the proposed technology and considered some of our initial projected outcomes to be too conservative, and that the system is capable of higher levels of performance.

The IH system incorporates proven and effective existing technologies. The novel aspect of this system is the rock injection mechanism into the lift system, giving rise to a new hoisting methodology, which Cementation has patented. Patents have been granted in several jurisdictions, protecting the IH system for transport of ore and waste rock from deep underground to surface.

IM: What criteria was the proof of concept model built for? What scale is it at? Where was it built?

APJ: A proof of concept, small scale system was constructed at the Cementation workshops in North Bay (Ontario). It was built using clear plastic pipe to study flow, to trial different slurry injection manifolds, and observe mixing, to evaluate the effectiveness and demonstrate production rates with 50 mm (2 in) flow lines over a height of 4 m. The principal of injecting a rock slurry into a constantly moving flow of carrier fluid was verified. The system consistently moved 37.5 kg in just over two minutes, equivalent to over 1,000 kg/h (1 t/h).

The Injection Hoisting system process with the rock injection mechanism into the continuous loop, carrier fluid lift system

The results led into the next stage for an envisioned prototype attaining 24 t/h (circa-500 t/d). Further engineering indicates the IH system is capable of higher levels of performance with projections for commercial systems scaled up to 150 mm (6 in) pipe, or 200 mm (8 in) heavy pipe capable of delivery rates in the range 1,000-2,000 t/d over a vertical lift of circa-600 m (up to 2,000 ft).

Systems would be scalable to perform as mine production increases (production and/or depth increase). Applications would include ore and waste hoisting from any underground mine as an alternative to traditional skip hoisting or trucking.

IM: Which applications currently have the strongest business case/are easiest to employ?

APJ: IH is an innovative alternative approach to conventional hoisting or trucking ore/waste rock from underground mines. The benefits are many and include:

  • Capital and operating costs reductions through – reduced shaft size and headings, reduction or elimination of the headframe and surface infrastructure, reduction in shaft station and shaft bottom excavation, elimination of expensive hoisting and/or mobile equipment costs;
  • Reduction of carbon footprint through lower energy consumption especially when compared with traditional mine truck applications, reduced carbon emissions through reduction/elimination of underground mine trucks, lower ventilation demand through reduction of trucking emissions that allows for smaller excavation cross sectional areas; and
  • A safer operating environment directly related to a reduction in exposure of workers to open holes and mobile equipment. The system would be intrinsically safer in both installation and operation. There are no issues in respect of current regulations in all the jurisdictions we have reviewed, which we see as an enabler.

IM: Is there a lot of interest in combining mechanised shaft sinking and development with this type of application where rock cutting could facilitate the size distribution that the pumps require without further processing?

APJ: This could be an ‘enabling technology’ for other developments, such as mechanised development or mechanised shaft sinking, to remove cuttings from the face/bottom. It could also be linked with large diameter raiseboring to remove muck the operating mine may otherwise not have the capacity to handle.

IM: What are the timelines for the next phase of the project (to construct and fully install a fully operational system in an underground mine)?

APJ: The next step is to install at depth a working prototype system based on a capacity of circa-500 t/d, and a vertical lift of 600 m. This would be suited to run-of-mine product reduced in size to <52 mm (2 in). The trial would prove the throughput tonnage, and provide the basis for development of a system capable of 1,000-2,000 t/d.

IM: What about potential commercialisation?

APJ: Studies indicate significant opportunities for capital and operating cost savings over traditional methods. Re-purposing existing, proven technologies reduce the risk of implementing this innovation, while maintaining existing maintenance procedures and skill sets.

With potential commercialisation, initial estimates based on a representative system capable of 500 t/d, from a depth of approximately 600 m, indicate a capital reduction of 30-50%; and operating cost reduction of between 30-70%.

Along with the reduction in capital and operating cost savings, there is time saving potential to reduce the overall shaft schedule by six months. Compared with trucking, the system has the potential for emissions reductions of approximately 12,250 kg/d of CO2. Other situations can be examined using project specific details and specifications.

Future business models for this technology could be varied, and it is open for discussion with interested parties to propose, develop and implement relevant commercial models.

Herrenknecht heralds ‘game changer for shaft sinking in soft and medium-hard rock’

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Having successfully excavated two 8-11 m diameter blind shafts using Shaft Boring Roadheaders (SBRs) at the BHP-owned Jansen potash project, Herrenknecht is leveraging all the lessons it learnt in Saskatchewan, Canada, to ensure this technology proves to be a “game changer” for the sinking of shafts in soft and medium-hard rock.

Mining contractor DMC Mining Services used two SBRs to excavate the blind shafts at Jansen, with the successful project completion acting as proof of the feasibility and advantages of the Herrenknecht SBR concept for the mining industry, according to the Germany-based company.

In August 2018, the mining industry milestone was achieved with the successful completion of two blind shafts to depths of -975 and -1,005 m, respectively, at the Jansen potash project. For the first time, shafts in the mining business were sunk using only mechanical excavation for this reference project.

Two Herrenknecht SBRs excavated the ground by a partial-face cutting method, using a cutting drum mounted on a telescopic boom. The excavated rock was then conveyed from the bench by an innovative pneumatic mucking system (PNM) and transferred into muck buckets to be hoisted to surface, the company said.

An innovative laser navigation system designed by the Herrenknecht subsidiary, VMT Group, using target units mounted on the SBR and lasers connected to the shaft wall, was used to keep the machines on track.

Herrenknecht, with its experience as a technology leader in mechanised tunnelling, developed the SBR for the mechanised sinking of blind shafts in soft to medium-hard rock. Based on the proven technology of the Herrenknecht Vertical Shaft Sinking Machine (VSM), the SBR offers improved safety performance compared with conventional shaft sinking methods while also achieving higher advance rates, according to the company.

The geological conditions at Jansen, however, were anything but easy. At a depth of around 450 m, the SBR encountered a layer of extremely hard competent rock causing excessive pick wear and low rates of advance. To overcome this and some further hardness challenges, the cutting drum was upgraded to a hard-rock cutting drum and torque output was doubled.

Because an existing high-pressure underground waterway, known as the Blairmore aquifer, posed a risk for water ingress into the shaft, ground freezing was executed temporarily in 2011 by BHP to a depth of approximately 650 m.

A major success in this difficult geology was the use of a mechanical ring erector, which allowed the installation of steel tubbing segments with minimal risk to personnel and a high degree of accuracy, according to Herrenknecht. The steel liner rings were installed through the Blairmore aquifer to assist in the development of a composite steel and concrete watertight liner in both shafts.

Since the project-specific design changes at Jansen required modifications to the SBRs, Herrenknecht, together with contractor DMC Mining Services, refined the SBR technology over the long term. The result is the second generation of Herrenknecht SBR technology.

As an example, the second generation SBR is equipped with an additional stabilisation level that allows the fixation of the SBR centre pipe on both ends. This ensures a stable transfer of the reaction forces from the cutting process to the shaft wall without movement of the machine – even with fluctuating excavation diameter of 8-11 m, as encountered at the Jansen potash project.

In addition to an improved filter system, a new design of the PNM system was installed in the second-generation machine, which results in a higher degree of separation in the suction tank itself, allowing wet material and even water to be handled.

Martin-Devid Herrenknecht, General Manager Mining at Herrenknecht, said: “The technical development of the second SBR generation is based on the lessons learnt from the Jansen project.” Two SBRs of this generation are currently in operation in Belarus and achieving good performance as a result of the improvements made, Herrenknecht said. “This pioneering approach is certainly a game changer for shaft sinking in soft and medium-hard rock, impacting the whole mining industry,” he said.

After the successful excavation at Jansen, another task was to be managed: the disassembly of the huge machines in the deep shafts. To remove the SBR from the shaft bottom, it was necessary to reduce the weight of the machine from 390 t to 340 t. This was achieved by stripping all components off the SBR that were in the excavation chamber. Both SBRs were safely extracted from the two shafts at the Jansen potash project in May 2019.

The Jansen potash project, located approximately 140 km east of Saskatoon, Saskatchewan, is a BHP-owned future potential potash mine with an expected initial mining output of around 3-4.5 Mt/y with valuable expansion options.

Agnico continuing to innovate at Kittilä gold mine as shaft project progresses

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Agnico Eagle is likely to leverage more innovation at its Kittilä gold mine in northern Finland judging by André van Wageningen’s presentation at the FEM conference in Levi, this week.

In a talk titled, Building future mines through collaboration, van Wageningen, Engineering Manager of the Shaft project at Agnico Eagle Finland, said the company was testing out battery-electric equipment and could potentially apply LTE in the underground mine next year.

Much of the battery-electric machine testing the company is carrying out at the mine is in partnership with the EU-funded SIMS project, but van Wageningen said the company has also acquired two electric bolters outside of the program.

As recently as last week, Agnico tested out an Epiroc MT42 Minetruck and ST14 Scooptram at the mine (pictured), with van Wageningen saying the trials had, so far, gone well, with operators noticing less heat generation and vibrations, and better air quality within the operating environment.

“The battery capacity is of course the main concern,” he said in answer to an audience question about how the electrified equipment had so far performed. “Our mine is designed to drive up and…[the machines] have a limited capacity for [that].”

On the topic of collaboration, van Wageningen mentioned that if Agnico had decided on the use of battery-electric and electrified equipment four or five years ago, it would have likely deepened the shaft further and redesigned the mine to suit the reduced ventilation needs and required battery charging/changeout infrastructure.

“If you go for electrification, you either do it or you don’t as you have to build charging stations for this,” he said, adding that these need to be plotted around the mine in relevant locations to ensure the machines are as productive as possible.

As it stands, the company plans to go down to 1,040 m below surface as part of an expansion plan at the mine to increase production by 25% to 2 Mt/y of ore. This could see Kittilä add 50,000-70,000 oz/y of gold to its profile.

The company is building the 5.6 m diameter shaft by, first, raiseboring to 4 m diameter and then slashing to 5.6 m, van Wageningen said. The company is then concrete casting the shaft.

van Wageningen said Agnico has raisebored down to 875 m, and the 94 m headframe was likely to be finalised in the very near future.

The deepening of Kittilä and the evolution towards using autonomous underground machinery is probably behind the company’s plans to leverage LTE communications at the operation.

Agnico is already a leader when it comes to LTE, having become the first company to roll out the communications technology at an underground mine – the La Ronde Zone 5 operation in Quebec, Canada. This move was predicated on Agnico trialling autonomous equipment underground at the mine. In its June quarte results, the company said results from these trials had produced “favourable” results.

BHP’s Jansen potash project set for early-2021 investment decision

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While uncertainty remains around the construction of BHP’s Jansen potash project in Saskatchewan, Canada, the company, in its September quarter results, confirmed it is still spending money on the asset prior to making a development decision.

BHP said the Jansen Stage 1 potash project will be presented to the board for a final investment decision by February 2021. The currently Stage 1 plan, which is in the feasibility study stage, involves building out initial capacity of 4.3-4.5 Mt/y of potash, with expansion optionality.

The miner has, so far, committed to spending $2.7 billion on the project. This is expected to result in the excavation and lining of the 7.3 m diameter production (975 m deep) and service (1,005 m deep, pictured) shafts – sunk by DMC Mining using Herrenknecht’s Shaft Boring Roadheader – and the installation of essential surface infrastructure and utilities. The overall Stage 1 project is expected to have a capital outlay of $5.3-5.7 billion.

In the September quarter results, BHP said in order to make a final investment decision, work on engineering to support project planning and on finalising the port solution is required. The BHP Board has, as a result, approved $144 million of spending for these activities, with an additional $201 million in funding set aside to further de-risk the project. The latter is focused on the mine’s scope of work, advancing other engineering and procurement activities, and preparation works for underground infrastructure, it said.

“This will enable an efficient transition of the project team between the study and execution phase, should the project be approved,” BHP said, adding that the release of funding to the project will be staged over this period.

The company, meanwhile, gave an update on its South Flank iron ore development, in the Pilbara of Western Australia, with CEO Andrew Mackenzie saying the project was 50% complete, with all major items on schedule and budget.

South Flank, which is expected to cost $4.6 billion to build, is set to replace production from the existing Yandi mine, which is reaching the end of its economic life. BHP is targeting first ore extraction at the operation in 2021 and expects to ramp up to 80 Mt/y of output.