A Mineweb Op-Ed exclusive by Dr Declan Vogt from the Wits School of Mining Engineering.
Johannesburg: Our deep level gold and platinum mines are in trouble. At today’s prices, most are not profitable. There are many explanations for the high cost: mines are getting deeper, infrastructure is old, and energy and labour costs exceed inflation. Given that we have little control over the price of the commodities, the only solution is improved productivity.
In many other industries, technology has enabled huge strides in productivity. Even in South Africa, almost all underground coal mining is now mechanised. So what about deep-level hard rock?
Technically, our orebodies present a challenge. Both the Witwatersrand and the Bushveld orebodies are hosted in very hard rock – quartzite and shales, or norites and anorthosites. The ore itself is also hard and abrasive, so rock cutting is not economic at present.
Conventional drill-and-blast mining can be mechanised, but orebody geometry is a challenge. The metal-bearing reefs are narrow, varying from centimetres to about a metre in thickness. The reefs dip at between about 10° and 30°, too steep for easy use of wheeled vehicles, but too level for broken rock to flow on its own.
Despite the challenges, there are extra-low profile (XLP) and ultra-low profile (ULP) machines available to mechanise the tasks of drilling, cleaning and supporting the face. They have started to be used in platinum mines, and roughly 30% of current underground production now comes from mechanised areas.
They have not yet been widely deployed in older mines that were designed for hand-held drill and blast techniques, for reasons mainly related to labour costs.
Witwatersrand gold mines are very large, relatively predictable orebodies, but have low ore grades. To make them payable, they must be operated on a large scale. At a time when labour was the only way of mining, they were only viable because of the low cost of labour.
For the rest of this column, click here: http://www.mineweb.com/news/platinum-group-metals/how-technology-is-going-to-impact-on-deep-level-mining-in-south-africa/