Modern Mining: Featured News

The Venetia Underground Project (VUP) of De Beers will not only extend the life of Venetia – South Africa’s biggest diamond producer – into the 2040s but it will also result in the mine emerging as a world leader in terms of the automation of mining operations. Modern Mining’s Arthur Tassell recently visited Venetia and spoke to Gerrie Nortje, Venetia’s General Manager, and Christoff Kϋhn, Head of the Venetia Underground Project (VUP), who confirmed that the decision had been taken to deploy autonomous trackless mobile machinery (TMM) in the new underground mine, which will start producing ore in 2021.

The Venetia processing plant.

In essence, the VUP involves creating a state-of-the-art underground mine underneath the existing open-pit operations at Venetia. The two kimberlite pipes to be mined are K01 and K02, with the mining methods selected being Sub Level Caving (SLC) for the bigger K01 ore body and a modified SLC system for K02. The K01 cave will produce 4 Mt/a and the K02 cave 2 Mt/a.

To access the ore bodies, two concrete-lined vertical shafts, each 7 m in diameter, are being sunk to a depth of 1 040 m, and a decline system for trackless equipment with a total length of 7 km is being developed. As of late November 2017, the vertical shafts were both down about 600 m from surface and on course to reach their full depth in 2019 while approximately 2 600 m of the decline system had been completed.

As has been widely reported, the US$2 billion VUP ranks as the biggest ever investment made by De Beers in South Africa and it certainly ranks as one of the biggest mining projects currently in execution anywhere in the world. Approved in 2012 with construction starting in 2013, the VUP is running on schedule. It will be the primary source of Venetia’s ore supply by the end of 2023 and by 2026 will have ramped up to steady-state ore production of 5,9 Mt/a. On present planning, the underground mine will have a life through to 2045 although there is scope to extend this as the K01 ore body continues at depth.

As Nortje explains, the VUP is essentially a life extension project for Venetia rather than an expansion. “The current open-pit operation is producing just over 5,1 Mt/a, which translates into around 4,5 million carats (Mct) of diamonds a year,” he says. “This represents approximately 30 % of South Africa’s annual diamond production and 3 % of world production. Once the VUP is commissioned and in steady state, Venetia will continue to produce 4,5 Mct/a despite the higher ore production the underground mine will deliver. This might seem puzzling – at least to the layman – but it reflects the greater ore dilution associated with underground caving operations.”

He adds that there is a “significant opportunity” for the VUP to produce at a higher rate than currently planned. “The K01 and K02 kimberlite pipes are each capable of supporting a mining rate of 4 Mt/a and we have sized much of the infrastructure of the VUP with this in mind,” he notes. “So the option is available to increase production at some time in the future although this would require a plant expansion.”

On the subject of automation, Kühn says that the Venetia underground mine will undoubtedly be a pacesetter. “We have decided to go for autonomous loading, hauling and long-hole drilling. All these technologies have been used at other mines around the world but we will almost certainly be the first diamond mine – and possibly the first mine of any type – to implement all three simultaneously. We will be engaging with the various OEMs who produce autonomous trackless mining machinery over the next year or two to determine which of them can best meet our needs,” he states.

Kühn points out that De Beers is no stranger to autonomous technology. “We put in a fleet of driverless trucks at the Finsch mine roughly 12 years ago in what was a pioneering move at the time – certainly in South Africa. The mine has since been sold to Petra but that fleet is still working today, hauling ore from the ore passes to the crusher stations.”

The primary motivation for going the autonomous route, says Kühn, is safety. “There is a huge reduction in ‘machine-to-man’ interfaces,” he explains. “The majority of the machines will be operated from a high-tech, air-conditioned control room on surface so clearly there will be far fewer people employed underground than would be the case with a conventional operation – in fact, we estimate a reduction of between 40 and 50 % of personnel underground. Of course, we also eliminate the problems associated with manual operation – such as driver fatigue – which are major contributors to accidents.”

Another benefit that Kühn points to is an improvement in asset utilisation. “Put simply, we’re going to have less equipment working over longer hours. In addition, we’re going to extend machine life. As has been proven at operations such as Finsch, autonomous operation leads to far less wear and tear on machines and can result in total run hours being extended by up to 50 %.”

Nortje emphasises that the reduced number of people required underground as a result of automation will only have a minimal impact on the size of the workforce at Venetia. “The potential – and I stress the word ‘potential’ – reduction in the total number of employees is just 5 %. What will change, however, is the profile of employees. There will be a greater need for people with technical qualifications as opposed to craftsman or artisan-type skills.

“One of the benefits, incidentally, of automation is that it will support Venetia’s drive to increase women in mining,” he continues. “Venetia is already doing well on this particular metric, as it has over 300 female employees in a total workforce – excluding contractors – of around 1 350 people. But our aim is to do much better and automation will undoubtedly help in this respect.”

Apart from autonomous operation, the VUP is pioneering in another key area. For the sinking of the vertical shafts, the mining and shaft-sinking contractor, Murray & Roberts Cementation, has deployed – for the first time in Africa – a new shaft-sinking methodology derived from its sister company, Cementation Canada.

As Modern Mining has explained in a previous article on the VUP, the new system involves the use of ‘sling down’ vertical drill rigs (VDRs) and vertical shaft muckers (VSMs) accommodated in the sinking stage. The VDRs, apart from dramatically reducing the number of workers required on the shaft floor during drilling, offer greater drilling precision than the jumbo rigs used in the past. As for the VSMs, they are equipped with long, extendable booms with jaws on the end and are operated from the stage in a remote-controlled manner. They clean the shaft floor faster and more effectively than conventional cactus grabs, at the same time providing far greater safety. The VSMs are also able to manoeuvre the kibbles – which can weigh a ton or more – into position, eliminating the potentially dangerous practice of handling them manually.

Both the drill rigs and the VSMs being used at Venetia were originally developed by a Canadian company, MTI, which later became part of Joy Global (now Komatsu). Each shaft at Venetia is served by two VDRs and two VSMs.

Delivery of explosives has also changed in the new method, with pumpable bulk emulsions being used – a more efficient way of charging holes than the stick-type explosives previously employed. For the VUP, the explosives are being supplied by AEL
Mining Services.

Kühn says that the primary reason for using the Canadian-shaft-sinking system for the VUP is its inherent safety. “It eliminates all concurrent activities, so you never have a situation where one team is working above another,” he explains. “Moreover, there are far fewer people required compared to conventional sinking. Typically, we have between seven and nine people working in each shaft at any one time, which is probably about a quarter the number you would need using traditional methods. We are very impressed by the system. It is clearly the correct strategy and we can see the results – for example, in the main production shaft, we have now worked for more than 500 days without an LTI.”

While the Canadian method may be safer, it is not necessarily faster and Kühn acknowledges that the average daily rate of advance of about 1,5 m is somewhat slower than expected. “In practice, this has not been a problem and we’ve been able to work around it,” he says.

Turning to the 6 x 5 m decline system, Kühn reports that progress has been excellent. “In 2016, we achieved a 55 % improvement in development rates and this year we’ve recorded another 15 to 20 % increase. We’ve built up real momentum and in October 2017 we achieved close to 175 m of development, which is a record. We have a single crew on site but with lateral development now underway we are mobilising a second crew, with a third crew to follow in March this year. Ultimately, we will peak at six capital development crews.”

The primary mining fleet deployed for the decline comprises Sandvik machines. Two Sandvik DD421 twin boom electro-hydraulic jumbos are used for drilling the face and for rock support and work in conjunction with Sandvik LH514 LHDs and Sandvik 40-t capacity underground haul trucks. All the equipment is owned by De Beers but operated and maintained by Murray & Roberts Cementation.

In all (and including the vertical shafts), Venetia Underground requires 50 km of development (and 234 km over the life of mine). Currently, just over 5 km have been completed.

The fact that the VUP will start delivering ore in 2021 is a feather in the cap of the VUP team. As Nortje points out, this is over a year earlier than originally anticipated. “As initially planned, there was very little overlap between open-pit and VUP production. The problem with this is it would have entailed a significant drop in production at the changeover point. We’ve now largely eliminated this. We’ll be bringing on stream the K2 cave in 2021 while open-pit mining of the K1 ore body continues until late 2023, at which point all open-pit mining ceases and Venetia becomes a 100 % underground operation.”

While the VUP focuses primarily on the development of the underground mine, some work will also have to be done on Venetia’s processing plant to ensure that it has the capacity to handle the 5,9 Mt/a of ore that the underground operations will generate. “The capacity of the plant very much depends on the characteristics of the material it receives, which can vary considerably depending on where we are in the ore body and we have, in the past, been able to process up to 6 Mt/a,” states Nortje.

“Realistically, however, we are going to have to carry out some modifications to ensure that plant capacity is not a constraint once the VUP is fully commissioned. Much of this will be debottlenecking but we have also taken the decision to install an XRT circuit after the DMS as a further concentration stage prior to final recovery. The technology we’re using has been developed in house by De Beers Technologies (DebTech) and has produced excellent results in trials in Johannesburg. We believe that the installation of this circuit will, on its own, get us up to 5,5 Mt/a capacity for more challenging ore types.”

He adds that the processing plant at Venetia is currently turning in an outstanding performance, with 22 run hours a day being achieved on a regular basis.

Finally, it is worth pointing out that implementing a project of the scale and complexity of the VUP is no easy task. To address the many challenges involved, the key parties to the project – De Beers, the EPCM contractor, WorleyParsons RSA, and the shaft-sinking and mining contractor, Murray & Roberts Cementation – work together in a ‘tripartite alliance’ in which the emphasis is on collaborative problem-solving.

“The three parties are united in their determination to deliver a complex world-class project on time, on budget and to the highest safety standards,” says Kühn. “We still have a long way to go but all the indications are that we are achieving these objectives and that the VUP will rank, once commissioned, as a truly major accomplishment, not only for De Beers but also South Africa’s mining industry.”

Photos (unless otherwise acknowledged) courtesy of De Beers.

Contact Modern Mining

Title: Editor
Name: Arthur Tassell
Email: mining@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

Title: Advertising Manager
Name: Bennie Venter
Email: benniev@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

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