|MadSci Network: Science History|
The deepest mine - at least the deepest I can find any record of - is the Western Deep Levels gold mine operated by the Anglogold company in South Africa. It's depth is 12,300 feet, or 2.33 miles. The gold ore is recovered by actual miners at this depth, so they would be the deepest anyone has been in the earth.
A particular problem in deep mining is that the earth gets hotter as you dig deeper. Mining companies use giant air conditioning units on the surface to send cool air down to miners at these depths. Anglogold has located a lucrative gold deposit at a depth of 3.0 miles, but the temperature at this level is estimated to be about 160 degrees, and they are trying to determine if there is an economic way to mine it. Obviously, to make the kind of investment needed for this sort of mine, you must be mining something very valuable, like gold. Most underground coal mines are less that 1000 feet deep.
The trend in underground mining is toward increased automation. Work is being done on developing robot machines with computer guidance - even to the point of operating the machinery from the surface.
Following is a copy of an article that has more detail about the Anglogold deep mining operations and plans.
From the Birmingham Post (a UK newspaper)- 5/30/98 GOLD MINES REACH NEW DEPTHS - INDUSTRY CONSIDERS SPACE AGE METHODS Miners in spacesuits. Robots digging round the clock. Colonies of men living and working for days under three miles of solid rock. These are a few of the ideas floating around South Africa's gold industry as it sets out to explore a 21st century frontier - ultra- deep mining. South Africa has the deepest mines in the world, but many shallower areas are mined out and the industry is probing previously unthinkable depths of three miles. The challenge has drawn mine executives, union leaders, government officials and scientists into a massive research project called Deepmine. "We'll be looking at everything from rock engineering to things that are real science fiction," Deepmine chairman Mr Keith Spencer said. The prize for going deeper than ever before is a vast reserve of gold at least equal to what has been mined already. It would extend the life of South Africa's mines well into the next century and Deepmine's expertise could be exported overseas. But getting to three miles and working there presents an enormous challenge. Deepmine has just approved several projects to tackle issues like shaft design, geology, financing, health and safety. The temperature at three miles is a blistering 70 degrees Celsius, while the pressure could pose other health problems for miners. Most mines use huge refrigeration units to pump cool air into tunnels as deep as 2.3 miles. But cooling costs at three miles may be too high, prompting experts to consider outfitting miners in climate-controlled suits. Others suggest using robots operated by remote control from the surface, able to mine 24-hours a day. Some futuristic thinkers have even proposed underground living quarters where miners could work and live for several days, much like an oil rig at sea. "We'll look at everything, but probably nine of out every ten science fiction ideas we'll throw away," said Mr Spencer, who is also technology chief at Gold Fields. Deep level mining is not new in South Africa. Anglogold, Gold Fields and Durban Roodepoort - the three gold companies in Deepmine - currently operate mines at more than 1.8 miles. Anglogold's Western Deep Levels is the world's deepest mine at 12,300 ft. Anglogold chief executive Mr Bobby Godsell kicked off the ultra- deep drive two years ago when he challenged his engineers to find a way to mine at three miles. Mr Godsell had his eye on a vast, lucrative gold reef called Western Ultra Deep Levels(WUDLS) . "I was the project manager at Western Deep south wondering how the heck we were going to get to four kilometres and here's my boss telling me we're on our way to five kilometres. It came as a bit of a surprise," said Mr Dave Diering, a deep mine experta t Anglogold. Anglogold has spent pounds 4.3 million on a 3-D surface seismic survey of WUDLS and plans a pounds 4.5 million drilling program. The area could hold up to 50 million ounces of gold. The National Union of Mineworkers, fearing job losses due to technology, is keeping a wary eye on the Deepmine project. Slumping gold prices have forced painful restructurings at the country's once-mighty gold firms, including thousands of retrenchments. Some experts believe today's labour-intensive operations would be too costly at ultra depths. "We are entering this whole exercise very cautiously," said NUM spokesman Mr Devan Pillay."It has not been shown yet that ultra-deep mining can be done with machines only."
While Deepmine's research may lead to new high-tech jobs for South Africa, the reality is ultra-deep mining will need fewer workers. "We cannot carry on with shafts that have 6,000 people. If that's the case, then South African gold mining has a finite life," Mr Diering said. He is confident the technology hurdles can be overcome without science fiction solutions, but the massivecostof building an ultra-deep mine may scare off investors. A five kilometre mine built from scratch could cost up to pounds 858 million and take 16 years before shareholders see a return. A cheaper option would be to use an existing mine, but that would still require billions of rand to develop. Ultimately, the gold price may have the final say on whether South Africa's mines break the five kilometre barrier.
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