Tag Archives: Drill and blast

Minnovare and LiveMine open up to collaboration, integration

Minnovare and LiveMine have entered a collaboration that, they say, will enable their mine production clients to share data across the business’ software platforms.

The data integration will enable production drilling information logged via Minnovare’s CORE (Client Online Reporting Engine) to seamlessly sync with the LiveMine data management system.

The combination of both technologies streamlines the workflow for the drill rig operator, eliminates the potential errors and ensures accuracy at each stage in the clients drilling process, providing the confidence the client needs to make informed decisions on data they can trust, the companies said.

Chris Davidson – Underground Manager at Silverlake Resources, a customer of both companies – said: “We like to partner with businesses such as Minnovare and LiveMine who not only provide industry-leading technology but take into consideration our feedback and the specific needs of our operation. This collaboration will streamline our process and eliminate duplicate information, meaning our team can have confidence to make smarter, faster decisions on data we can trust.”

LiveMine is a data collection and management solution that integrates with existing operations to eliminate inaccurate reporting and wasted time. It eradicates hours of paperwork, unreliable spreadsheets, uncertainty in data accuracy and helps bring mining operations into the 21st century, the company says.

Coming in underground, open pit and exploration modules, LiveMine offers contractors and owner operators a way to collect and manage their operational data. Being able to use this online or offline means clients can collect crucial operational data directly at the source in real time.

Minnovare CORE is a software platform that serves as a data hub for clients’ entire drilling operations. The platform is central to Minnovare’s Production Optimiser, a drill and blast optimisation system that substantially improves production drilling accuracy and consistency, resulting in less re-work, improved dilution and recovery and an increase in stope turnover in underground mines.

“This secure cloud-based platform features digital drill plans and plods that sync seamlessly with existing mine planning software, providing accurate, reliable and real-time drilling data to mine operators,” Minnovare says. “Visibility and accountability are then ensured by displaying the recorded drilled information in the cloud.”

Live Mine Managing Director, Bud O’Shannessy, said: “This is an exciting collaboration in terms of the value and simplicity it brings to our client’s operations. Minnovare deliver an innovative solution and, when coupled with the LiveMine system, it centralises the drilling and operational data and generates a single data source and approval process. LiveMine share a large client base with Minnovare, and this collaboration is client driven. Our clients have been asking for it.”

Minnovare Managing Director, Callum McCracken, added: “We welcome the collaboration with a leading data management software company like LiveMine, as we see the strength of our joint offering for our clients in terms of immediate and downstream benefits in their operations.”

Rhino raiseborer set for work in Botswana, South Africa

Having been introduced to the southern African market only a year ago, two Rhino 100 ‘plug-and-drill’ raiseborers from Sandvik Mining & Rock Solutions are already destined for local mining sites.

One unit will soon be at work in Botswana, while the second will be delivered to a large South Africa mine later this year, according to Saltiel Pule, Sandvik Mining & Rock Solutions’ Business Line Manager for Underground Drilling in southern Africa.

“This machine has raised considerable interest in our market, and we fully expect to see five units at work in our region by the end of 2022,” Pule says.

The primary application of the Rhino 100 is for drilling of production slots, but it also makes a valuable contribution in a range of other applications – from ventilation raises and escape routes to ore passes and connections between tunnels, the company said.

“Using conventional drill and blast methods, these vertical or inclined holes can take mines three to six months to complete,” Pule says. “With the Rhino 100, we are talking about durations of less than a week.”

Drilled as relief holes in sub-level open stoping, slot raises provide the necessary void space for blasting, allowing the expansion of blasted rock into the void to improve fragmentation.

Dean Zharare, Sales Engineer for Underground Drilling at Sandvik Mining & Rock Solutions, says the conventional blasting of slot raises often creates a bottleneck for mines.

“We have encountered situations where mine personnel have to return two or three times to a slot raise before it is ready, due to misfires, for instance,” Zharare said. “This creates a bottleneck in the mining process, reducing the monthly metres achieved.”

The mobility and drilling speed of the Rhino 100 can transform this scenario, he says, with an expectation that monthly metres drilled could improve by 65%. There is even the possibility that one of the units in South Africa will be operated remotely with the operator based on surface while it drills underground stopes.

Drilling holes of 750 mm in diameter, the Rhino 100 boasts penetration rates of about 2 m/h, more than double the rate of conventional methods, Sandvik claims. As important as the speed, Zharare says, is the reliability of the result.

“These larger holes make the blast much more reliable, avoiding any time consuming and dangerous redrilling in the event of a block ‘freezing’ after an unsuccessful blast,” he says.

Underpinning the machine’s mobility is its ability to carry its own components, including rods, cables, hydraulics and the raiseboring head. It is pulled by a specially adapted double-axle John Deere tractor. To optimise the set-up time – which can take as little as 10 minutes – it has outriggers for stability rather than needing a concrete pad to be poured. No roof bolting is required either, as an inclinometer gives the operator the necessary coordinates for a surveyor to confirm before drilling operations begin.

Since the Rhino 100 was launched 2017, it has achieved a strong global footprint, with over 20 units operating worldwide. Australia has seen particularly strong take-up, with one contractor already ordering four machines. Underground expansions at almost a dozen operations around southern Africa present exciting opportunities for the future of the Rhino 100 in this region, Zharare says.

The Rhino is manufactured by TRB-Raise Borers in Finland but is equipped with Sandvik tools and is distributed by Sandvik.

Newmont’s Canada mines hit wireless initiation milestone with Oricas WebGen

Newmont has continued to leverage the benefits of fully wireless initiation in its blasting process, having initiated its 500th blast using Orica’s WebGen™ system at its Canada mines.

The milestone was achieved at three of its underground mines in Canada, which are blasting with WebGen. Each site uses different mining methods, and all have achieved improved performance and safety in their overall mining processes with the implementation of innovative WebGen-enabled mining techniques, Orica says.

“The key to Newmont’s success was its ability to think differently and to take advantage of pre-charging with ‘no strings attached’,” the company added. “Eliminating the physical connections to each blasthole and the need for re-entry allowed the blasting sequence to be arranged for optimised outcomes.”

The blasting process changes help mines deliver significantly improved ore recovery and has simultaneously reduced interactions, cycle times and rework, according to Orica. WebGen wireless blasting technology is an innovation that enables process change unlike any other, by pre-charging blasts and firing blasts after access to the area is lost, it claimed.

Newmont’s WebGen journey started at the Musselwhite mine in late 2016 following Orica’s launch of the first-generation wireless initiation system, WebGen 100. The Orica technical team identified an opportunity to use the new technology and approached the Musselwhite team with a new concept, the “Temporary Rib Pillar (TRP) Avoca Mining” method.

Over the following months, workshops, detailed design reviews, risk assessments, crew meetings and signal surveys were completed and the first TRP stope was designed and ready to be blasted.

The initial stope was drilled and loaded in November and December 2016 and fired in January 2017.

Over the next year, the Musselwhite and Orica teams continued to use and refine the TRP method.

“As confidence in WebGen 100 increased, the teams explored other opportunities where wireless blast initiation could significantly improve safety and stope performance,” Orica said. “Several other wireless enabled mining methods were developed and evaluated through these collaborative efforts throughout 2017 and 2018.”

The results so far from the WebGen collaboration include a 20% reduction in mucking time, 14% improvement in production tonnes per day and 34% reduction in ore dilution.

Following the success of Musselwhite gold mine, the team from Éléonore Mine approached Orica in late 2018 to explore the possibilities of implementing the WebGen system on-site. The team conducted a two-day face-to-face workshop where the technical and operations teams from Éléonore and Orica met and conducted an in-depth review of Éléonore’s production mining operations.

The workshop ended with a commitment to complete a joint wireless blasting optimisation project, Orica said.

“A project charter was developed, which involved a detailed 10-stope evaluation across various geometries with the primary goal to improving stope recovery,” the company explained.

“Preparation started in early 2019 with detailed design sessions, signal surveys, risk assessments and crew information sessions.”

The first stope blast was loaded in February 2019 and fired in March. The project’s scope was completed by late summer and the project delivered and exceeded all the agreed performance metrics, according to Orica.

Sill pillars at Éléonore represent a challenge for both ground control and drill and blast teams.

“WebGen technology allowed us to safely and efficiently recover side-drilled stopes by greatly reducing worker exposure and stope cycle time,” Ugo Marceau, Drill & Blast Engineer at Newmont Éléonore, said.

Results from the WebGen introduction at Éléonore include an 86% increase in ore recovery, 72% reduction in stope time and 71% increase in drilling rates.

While the Éléonore project was underway, teams from Borden and Orica had already “white boarded” various wireless enhanced stoping scenarios to increase mining efficiency in Borden’s complex geometry.

“The main goals were eliminating as much lateral development and cemented rock fill as possible while maximising ore recovery,” Orica explained. “As with both Musselwhite and Éléonore, signal surveys, risk assessments and crew information sessions were completed to prepare the first stope.”

Borden’s first stope was loaded in early April and fired later that month. Once again, the outcomes from using WebGen exceeded those expected from a conventional approach, according to Orica.

Eric Fournier, Mine Engineering Supervisor at Newmont Borden, said: “Orica have been partners with us from the very beginning. The WebGen team is very professional, knowledgeable, and easy to work with. The technology is great but the people behind it make it happen. WebGen technology allows us to be a safer and a more efficient mine. It removes the need to send people around hazardous conditions that exist after a blast.”

Results from the Borden implementation include 98% actual ore recovery and 17% actual dilution.

Orica concluded: “Wireless-enhanced production mining has been expanded across these three Newmont mines. The WebGen system has proven itself as a reliable initiation system and enables drill and blast engineers to modify existing mining methods for substantial improvements in safety, productivity and cost reduction. This has been an exceptional journey together with Newmont and highlights the results that can be achieved through innovation and collaboration.”

CSI to carry out load and haul, drill and blast work at Rio’s Brockman 2 iron ore mine

Mineral Resources Ltd’s CSI Mining Services has been awarded a mining contract by Rio Tinto to carry out work at the Brockman 2 iron ore mine in the Pilbara of Western Australia.

The scope of the contract will see CSI conduct load and haul, drill and blast, and short-term mine planning activities for Rio, the company said.

This will involve scheduling, drilling and blasting and then excavating 27 Mt of waste rock and iron ore over an approximate nine-month period, with a fleet of large-scale mining equipment, developing the Lens A/B pit for Rio.

This contract builds on a 16-year relationship with Rio, dating back to when CSI first commenced crushing services at the Nammuldi mine site. It also follows the completion of a 30 Mt load and haul contract at Rio’s Tom Price mine. CSI remains engaged at another Rio Tinto operation, Paraburdoo, where its team is carrying out 13 Mt of load and haul operations.

The Brockman 2 contract will generate around 150 jobs for CSI’s highly skilled workforce, the company said.

Mineral Resources’ Chief Executive Mining Services, Mike Grey, said: “We are delighted to have been invited by Rio Tinto to assist at another of its world-class iron ore mines. Our relationship with Rio Tinto dates back 16 years. Since then, we have been able to establish a track record of consistent project delivery for Rio Tinto, which we are very proud of.

“CSI is the world’s largest crushing contractor, so it is immensely satisfying that this latest Rio Tinto contract includes other mining activities, such as load and haul and drill and blast, to demonstrate CSI’s diverse skills set. We are confident this Brockman 2 scope of work will become the latest chapter of our ongoing association with Rio Tinto.”

Brockman 2 is one of the 16 mines that make up Rio’s world-class Pilbara iron ore operations.

The CSI team has begun mobilising to site, including delivering a new fleet of Komatsu 830E electric-drive dump trucks and a new Komatsu PC4000-11 excavator.

Barrick Hemlo boosts productivity with Orica wireless blast initiation solution

Orica says testing of its WebGen™ 100 solution at Barrick Gold’s Hemlo mine in Ontario, Canada, has shown wireless blast initiation can improve the economics of its Alimak stoping.

In early 2019, Hemlo’s management team approached Orica and Manroc to explore opportunities for improvement via the application of wireless blast initiation. Through a series of workshops, Orica and Barrick Hemlo worked together to identify opportunities to use WebGen 100 wireless through the earth initiation technology in its Blind Alimak Mining application.

This Blind Alimak Retreat (BAR) concept was aimed at improving both safety and productivity, and included:

  • Reduced exposure time related to Alimak entries;
  • Improved ore recovery from 70% to over 90%;
  • Increased recovery by maximising blast design, sequence, and available void;
  • Increased mucking rates while decreasing cycle time; and
  • Optimised crew logistics by using single pass loading.

To expand operations and aid in the longevity of mine life, both efficiency and recovery were top priorities for the Hemlo team, Orica said.

Alimak Mining is normally done either in small repetitive blasts cycles, from the bottom of the raise up to an upper sill, or, in the case of blind Alimaks, as a mass blast into the void that exists in the raise and undercut below.

Given that access is lost after the mass blast, the size of the blast (Alimak height) and recovery is often restricted by “free face” and available void. At Hemlo, the Blind Alimak blast performance was limited by underbreak in the top third of the Alimak (footwall break) due to the available void becoming choked off during blast progression. Using wireless blasting technology, the team was able to eliminate all void limitation, Orica said.

The solution was to develop a blast design with optimised burden and spacing as well as timing and blast sequencing, allowing well-defined portions of the Alimak stope to be taken at the appropriate time. Single-pass loading was used to achieve the safety and productivity benefits.

Breaking the Alimak stope into five pre-loaded portions (each increasing in size to capitalise on void created during the excavation process) allowed for flexible blast management throughout the mining process, Orica said.

“With the ability to merge and increase blast sizes based on in-field results, the operation had unprecedented control and was able to operate outside of the traditional constraints of mining cycles,” it added.

With three days of continuous loading, Hemlo was able to achieve a month-and-a-half worth of blasting while freeing up the Alimak crews to move on to the next stope, according to Orica. To maximise the blasting sequence, the first blast (wall slash and five rings) was blasted with Orica’s i-kon™ III Electronic Blasting System. The next three blasts (two merged) were fired with WebGen 100 units when ready, with performance verified with bucket counts and CMS.

The results of the project stope were extremely positive and proved that wireless blast initiation can improve the economics of the Alimak stoping, according to Orica. Key benefits included significantly reduced personal exposure (reduced by over 50%), increased stope recovery and cycle time. The success of the Alimak has also led to the introduction of wireless blasting into large blind up-hole patterns at Barrick Hemlo, solving similar issues to that of the Alimaks, Orica said.

The outcomes of this project delivered a 40% improvement in productivity through decreased cycle time, faster mucking rates, improved ore recovery from 70% to over 90%, and increased safety by eliminating countless re-entries and hookups, while stripping rail and logistically simplifying the operations process.

Recovery improvement and productivity gains delivered significant value and increased revenue for the customer, Orica added.

“The project has also shown the ability to increase the height of blind Alimak stopes without concern for available void, thereby eliminating the need of top sill development moving forward,” it said.

This successful trial has led to full-time technical collaboration with Barrick Hemlo mine since the end of 2019. Including this evaluation at Hemlo, Orica has successfully fired more than 50 wireless initiating system blasts loaded with over 2,700 WebGen 100 units.

SRG Global to help Red 5 blast off at Great Western gold mine

SRG Global has been awarded a term contract with Pit N Portal Mining Services to provide specialist production drill and blast services and explosives supply at Red 5 Ltd’s Great Western gold mine in Western Australia.

The term contract is expected to start immediately for an initial 12-month term.

Pit N Portal, a division of Emeco, was awarded the contract mining gig at Great Western back in October.

A satellite deposit located around 55 km from Red 5’s Darlot gold mine and processing facility, Great Western comes with a measured, indicated and inferred resource of 870,000 t grading 2.5 g/t Au for 70,300 oz of contained gold. The maiden proven and probable reserve totalled 437,500 t at 2.5g/t Au for 35,424 oz of contained gold.

Based on a proposed mining rate of between 30,000-40,000 t/mth of ore, the open pit is expected to be completed over a period of around 13 months, with plans to then access the underground orebody via a portal at the base of the pit, Red 5 said at the time.

In addition to the work on Great Western, SRG Global was also awarded a new three-year contract (with option for a further two years) with GFG Liberty OneSteel to provide engineered access solutions at the Liberty Steelworks site in Whyalla, South Australia.

David Macgeorge, Managing Director of SRG Global, said: “We are very pleased to have secured these two term contracts, adding to our recurring annuity earnings.

“The Pit N Portal contract was specifically targeted as it builds upon our mining services portfolio of high-quality growth commodities whilst diversifying SRG Global’s customer base.”

Thiess cuts probe drilling costs by leveraging advanced void management system

Thiess says its mine planning team is pioneering the development and use of an advanced void management system that is informing probing, drill pattern and blasting design.

The holistic system gives the contractor’s office and field-based teams immediate access to a central database of void information to support better, faster decision making and task optimisation.

Thiess General Manager WA/SA (Acting), Matt Henderson, said the system focuses on capturing, monitoring and understanding existing voids to help the project team manage and backfill where required.

“It gives us and our client a clear understanding of the geological and geotechnical risks associated with the project and how to best address them,” Henderson said. “This flows from mine design into operations, enabling our project team to manage and mitigate risk to our people and delivery.”

Thiess Mine Planning Manager, Ravi Achari, said the system, designed to enable verticle mining through extensive networks of underground voids (drives, development workings, workings, vertical rises and large slopes), was developed to improve safety and provide greater certainty in the company’s delivery.

“The system was developed using insights and learnings from a number of technologies currently available on the market, but without integration were unable to provide the required outcome,” Achari said. “We also leveraged insight from our void officers and surveyors, and drill and blast, geotechnical and mine planning engineers.”

Achari confirmed the new system enables his team to determine the right solution specific to each void.

“The system uses historical plans, probing and drilling data to survey the position and size of the old workings,” he said. “This includes checking the location and attributes of the voids we find against the recorded data to verify any changes in size or shape.

“Our findings will then inform our safety zone and backfilling requirements.”

Incorporating over five-years of proven void management processes and procedures, the system delivers client benefits by enabling Thiess’ team to mine additional tonnes.

“The system gives a precise delineation of the voids informing a more tailored drill and blast design that allows additional recovery of the commodity,” Achari said. “It has also enabled a reduction of probe drilling costs by up to 25%, representing a substantial cost saving.”

To date the system has helped manage and treat over 25 km of underground voids and stopes in Western Australia, and is currently being leveraged to develop an integrated drill and blast reporting system for Thiess globally.

Hexagon adds colour to drill and blast process with HxGN Split HSL

Hexagon has, once again, looked to improve fragmentation analysis within the drill and blast process by adding split colour features to its offering.

HxGN Split provides technologically advanced image-analysis techniques to help mines optimise fragmentation, saving significant costs while improving drill and blast processes, the company says.

New to Split’s solution suite is HSL (Hue, Saturation and Luminance), a colour analysis feature that empowers mine operators with real-time detection of ore types.

“Real-time tracking of product types allows for immediate decision making to optimise rock-size reduction and product-type treatments,” Hexagon says. “The new feature further supports operational efforts to improve product throughput and ore recovery.”

This is important when mining operations are continuing to maximise existing resources, using value-added technologies.

HSL’s key benefits include:

  • The ability to monitor product type blending for optimum processing;
  • Reduce ore dilution by tracking product source mining;
  • Maximise throughput with consistent product delivery to the plant; and
  • Immediately adjust ore recovery treatments based upon product type.

“Hue, Saturation and Luminance values are measured during live plant production and provide a statistically relevant sample required to aid decision making,” Hexagon says. “A colour wheel is applied to the images to provide calculated HSL values for every processed iteration. Evaluation of the Split HSL values are correlated to the mine geologic product types to find the unique image property signatures.”

The HSL values are measured for the image samples to be trended on live operator screens. Step changes in the Split results provide immediate indicators for product type changes that signal the need for operational responses, Hexagon says.

Timely decisions surrounding the operating conditions lead to improved plant throughput and product recovery, while additional detailed measurements for individual rock particles can be measured using the same Split HSL measurements to find the ratios of the product type blends.

The company concluded: “Drill and blast is a notoriously complex, multi-layered process. HxGN Split’s image processing technology delivers high-quality information, ensuring the key step of fragmentation analysis is managed from drill to mill, thus improving mine profits.”

Orica leverages MWD data, AI to create new blast loading design benchmark

Orica is looking to set a new benchmark for blast loading designs in Latin America after deploying its Design for Outcome solution in the region.

The company, focused on integrating its digital blasting tools to improve outcomes, is leveraging its BlastIQ digital blast optimisation platform within this new solution, Angus Melbourne, Chief Commercial and Technology Officer of Orica, told delegates at Massmin 2020 last week.

In a presentation titled, ‘Blasting’s Critical Role in Extracting Ore’, Melbourne mentioned Design for Outcome as an example of where the company was delivering integrated digital solutions in Latin America.

“Design for Outcome is an automated continual optimisation solution that sets a new benchmark for blast loading designs,” he said. “It utilises data science to process both upstream and downstream data to automate blast designs. This produces tailored and optimised blast designs by reducing blast variability and explosive consumption while increasing productivity.”

Using machine-learning algorithms, Design for Outcome processes measured-while-drilling data to classify ground hardness throughout each blast hole and then match explosives energy to hardness domains to automatically generate tailored blast loading designs, Melbourne explained.

Through artificial intelligence, these algorithms are trained with the data received from the fleet control systems (FMS) and previous blast results. This enables final automation of the blasting design process and its execution in the field with Orica’s smart control systems and programming interfaces, loading the blast accurately according to the generated design. These elements combine to ensure the desired outcomes are achieved, Melbourne said.

“Digitally-enabled blasting solutions such as Design for Outcome are allowing us to work with customers in different ways, to think and act differently and expand our role in the mining value chain,” he said.

Such a solution is part of the company’s plans to automate its segment of the mining process. This goal was strengthened last month with the launch of the Orica and Epiroc jointly developed Avatel™ semi-automated explosives delivery system.

A key enabling technology of Avatel, which is built on the foundation of Epiroc’s Boomer M2 carrier, and Orica’s automation vision is WebGen™, the company’s fully wireless initiation system. When combined with Orica’s LOADPlus™ smart control system, specifically designed on-board storage, assembly, digital encoding capability and Subtek™ Control bulk emulsion, Avatel provides customers with complete and repeatable control over blast energy from design through to execution, Orica says.

While referencing the second key pillar in Orica’s digital strategy, Melbourne highlighted the use of the company’s Bulkmaster™ 7 smart, connected explosives delivery system in Latin America during the virtual event.

The new delivery systems not only improve productivity but begin to digitise critical workflows between design and execution in drill and blast operations, according to Melbourne.

The Antamina copper mine in Peru, a joint venture between BHP, Glencore, Teck and Mitsubishi, will soon be leveraging such a system, with Melbourne confirming seven Bulkmaster 7 units had been shipped to the mine and were undergoing commissioning.

Orica’s third digitalisation pillar is the measurement of downstream impacts of the drill and blast process, which is where FRAGTrack™, the company’s automated rock fragmentation measurement device comes into play.

This device captures, analyses and reports real-time data for optimising blast operations, improving downstream productivity and tracking overall operational performance in mining and quarrying, Melbourne explained.

This system is active across several key customer sites in Latin America, with Teck’s Carmen de Andacollo operation in Chile being one of the first to adopt the technology in the world, according to Melbourne. He said the copper operation is using the insights to deliver efficiencies across the value chain through digitally enabled optimised blasting.

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.