Modern Mining: Featured News

While the spotlight has in recent years favoured the underground project at De Beers’ Venetia diamond mine, the open-pit operation has quietly been producing the goods; it is now further raising the bar in operational standards as it heads into its ‘final straight’ of just five years.

According to Russel Horak, Venetia’s Senior Mining Manager, the current focus is firmly on driving efficiencies and applying best practice principles to ensure that operations remain optimal even as the production tails off between now and the planned closure of open-pit mining in 2023.

“The mining team has been boosted with key staff who have the experience and passion required, and who take huge pride in their work,” says Horak. “With our focus on constantly improving mining practices, we achieved 36 million tonnes (Mt) in 2017 – an increase of 25 % on our 2016 levels.”

                      The K2 pit with the new shafts in the background.

This contributed substantially to diamond production in 2017 of 4,6 million carats, a 27 % increase on the 2016 total of 3,6 million carats. Venetia is targeting 27 Mt total tonnes for 2018 as it gradually ramps down towards the start of underground mining. After that, production drops off steeply year on year to 3,2 Mt in 2023.

Horak emphasises the importance of ensuring that spatial and operational constraints in the pit are identified and minimised to allow mining to continue efficiently.

“This means optimising the utilisation of equipment and expertise of the workforce, with a focus on applying good mining practices that avoid any rework as far as possible,” he says.

Venetia’s Acting Section Manager Mining, Stephanie Bleker, points to the key role of quality drilling and blasting techniques in facilitating efficient loading and maintaining high production levels.

“We pay close attention to drill and blast quality to achieve good fragmentation and diggability for increased loading rates,” says Bleker. “As importantly, this also results in more stable highwalls that require less scaling, allowing us to optimise our slope angles thereby mining more kimberlite.”

The appropriate sizing of the blasted material in turn provides benefits to the downstream ‘customer’ – the 6 Mt/a process plant – which can in turn operate its crushing and processing facilities at high efficiencies.

Bleker also emphasises the importance of conducive conditions in the pit provided by the mining staff – such as maintaining good haul roads so that truck speeds are not compromised and equipment life is maintained.

Safety and health continue to rate as priorities in terms of De Beers’ Zero Harm philosophy, and Venetia invests regularly in technology upgrades that help mitigate incidents in the pit. One such recent advance has seen the capacity of the pit mesh network expanded to carry greater levels of video, radar data and fatigue data from the trucks and other equipment to the central control centre. This is part of the mine’s ever-improving proximity detection system and fatigue management system to prevent incidents.

To make the best use of the in-pit equipment over the next five years, the role of contractors will be important to even out the capacity where necessary. While the mine had 38 of its own haul trucks in operation last year, this is down to 35 trucks this year. Similarly, the number of shovels is down from six last year to four Cat 6060 units with a 28 m3 bucket configuration. Five large mine-owned drills conduct the production drilling in the pit, while there are seven smaller drills operated by a contractor to conduct the trim and pre-splitting drilling.

“By reducing the equipment fleet we are also achieving better efficiencies, with some machines being put on care and maintenance while others take on more hours,” says Horak. “Careful analysis of the benches to be mined, the dump deposition strategy, the cycle times and all relevant data allows us to forecast our primary equipment requirements year on year; we then align our ancillary equipment to these plans.”

With approximately 1 288 employees at Venetia, he says the future integration of the open pit with underground operations is already in the planning stages, with the mine considering the range of implications for staff, infrastructure and other issues. The intention is to absorb as many employees as possible into the new phase of the mine, in order to retain as much of the company’s valuable skills base as possible.

The environmental rehabilitation work – conducted on a concurrent basis – has been particularly successful, he says, with rock dumps being covered with topsoil, seeded and grassed on the northern side of the property. As the mine itself will not be closing, the end of the open pit will not necessitate a closure certificate, but rehabilitation work will be ongoing.

Water management remains a focus at Venetia, especially since significant floods in 2013 caused major disruption. Facilities are now in place to mitigate a 1-in-200-year flood event, with pumping facilities in place at Bench 15 to dewater the pit’s main sump. The mine conserves large quantities of water by re-using rainwater from the pit. There are three dams in place as well as a circulation system that allows this water to be used for non-potable purposes like dust suppression and in the plant.

Report by Paul Crankshaw.

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