As openpit mines reach their economic end of life, mine owners are considering the viability of transitioning their opencast mining operations to underground, says global engineering firm Worley.
Using its deep-level mining expertise in South Africa, Worley assists mine owners around the world in exploring the feasibility of underground life-of-mine extensions and identifying the most efficient and safe underground mining methods.
Among the driving factors in the transition to underground mining are declining ore grades, deeper ore deposits, and an increase in demand for minerals required for the global energy transition, such as copper, lithium, manganese and nickel.
Worley’s centre of excellence for copper in Chile has been supporting openpit copper mine customers for nearly three decades. The company is gearing up its underground capability as these mines shift their operations to below surface to access deeper ore reserves.
Going Deep in South Africa
It stands to reason that Worley’s South African operation is one of the company’s mining centres of excellence with niche experience in deep-level mining. The first deep underground mines were built in South Africa. The country is known to have some of the world’s deepest mines, including the world’s deepest gold mine, descending over four kilometres.
Mining has been the mainstay of South Africa’s economy for well over a century, and a major source of employment as well as foreign investment. Consequently, Worley has grown its South African mining team, with a collective experience of over 120 years in deep-level mining and process expertise.
Worley Mining, Minerals & Metals in Africa VP Robert Hull says that its South African operation is recognised for its deep-level shaft experience, and the company also has experience across most commodities including base metals, coal, platinum, gold, diamonds and ferrous metals.
Hull says that Worley has a strong global workshare philosophy and culture of collaboration. The specialist skills in South Africa gained from working on some of the biggest underground projects in the world are an integral part of Worley’s global project delivery offering.
Deep-level Mine Skills
Some of South Africa’s specialist deep underground skills include shaft design, ventilation and refrigeration shafts, high pressure pumping, and deep level hoisting.
Worley is one of the few companies in the world that has the expertise to design hoisting systems for mass hoisting, such as at the Venetia Underground Project, which will hoist about 6-million tonnes of rock a year.
The firm explains that De Beers’ Venetia mine, in South Africa, is the biggest source of rough diamonds in the country, and that the mine is in the process of transitioning from openpit to underground, to extend its life by some 25 years.
“As [engineering, procurement and construction management] contractor for South Africa’s largest mining execution project, Worley is utilising three-dimensional (3D) designs for the project infrastructure to provide 3D models for the entire project’s surface and underground infrastructure.”
Hull says that Worley is leading the way in developing digital solutions for the planning, design and execution of mining projects. “The South African office has played a key role in the design and development of much of the group’s digital technology in mining and minerals processing.”
He cites the Wafi Golpu, Papua New Guinea feasibility study update where the South African team drew on SmartPlant design technology, which uses rapid prototyping and Building Information Modelling. The technology allowed the entire project team to visualise project objectives “as never before”, thereby improving operational efficiency in a dynamic time- and cost-saving environment.
“The Wafi Golpu project is ranked as a world-class deposit in terms of its size and the grade of gold and copper within it. If developed, it will be the largest, deepest and most complex underground mine in Papua New Guinea, with a mine life of 28 years,” Hull notes.
Worley’s South African team is also supporting its Australian counterparts to project manage the delivery of the deepening and expansion of an underground gold mine. This includes construction of a 1 460 m shaft, additional capacity in the processing plant, and supporting infrastructure to enable profitable recovery of ore at depth to 2 140 m below surface.
Hull says that every underground project that Worley has executed has drawn on the company’s large materials handling capabilities. “In South Africa, we have a dedicated materials handling department that has the latest tools, including discrete element modelling and finite element analysis, and advanced simulation tools for conveyer design.”
Coenie Mynhardt, who is part of the winder engineering team at Worley, adds that mine payloads have increased dramatically in the last two decades in pursuit of higher productivity rates.
“Mines such as Impala and Phalaborwa in South Africa, with an [estimated] 12 t per skipload, were considered ‘mega mines’ in their day. The mines of the future are more than double that size.
“The mega mines of the future need mega machines to be able to handle such big payloads,” says Mynhardt. “Materials handling technology for such deep, high tonnage operations will test current technology for capacity and reliability to bring the ore from the production levels to surface. We have the skills and expertise to find the solutions to these challenges.”
Global Project Delivery
“Countries such as Chile have immense potential for transitioning from openpit to underground if the geology supports it,” comments Hull. “With the wealth of experience across locations and over 4 000 staff in our mining, minerals and metals business line, we can safely and successfully deliver our customers’ underground mine assets through collaborative development of the mine and associated infrastructure anywhere in the world.”
Worley is a networking sponsor for the 2020 Joburg Indaba, which will be hosted as an online event on October 7 and 8.