Depth and Death for South Africa's Gold Mines
Source: Reuters, Ed Stoddard (6/6/11)
"The bottom has not yet been hit. . ."
The massive drill is deafening as it bores into the rock of the world's deepest mine, where heat and humidity sap the strength of gold miners who never know when the next rock fall might kill or maim.
At 3.8 km (2.4 miles) underground, it feels like the bottom of the world.
Toil and blood have brought humans to this spot, the lowest in AngloGold Ashanti's Mponeng mine, 60 kms (35 miles) southwest of Johannesburg.
Tremors can be fatal, and the following day a rock fall in the mine killed a workerthe first death in 2011 at Mponeng.
Mining was halted while it was investigated, which has become standard procedure since South Africa set out to cut the heavy death toll in mines, chiefly among black workers, that the authorities tolerated before white minority rule ended in 1994.
Reaching the bottom of Mponeng is an ear-popping journey down a shaft in a massive, cramped and dark cage. It involves travelling to one level, switching cages, then descending again.
Ray Durrheim, who holds the research chair in seismology at Johannesburg's University of the Witwatersrand and formerly headed a project called the DeepMine Research Programme, said as you go deeper there are safeguards that can be put in place.
"You try to compensate for the depth by introducing stiffer backfill like cement," he said. You can also shorten the distance between support pillars and use bigger pillars.
The bottom has not yet been hit. "Technically, we don't see why you can't go down to five kilometres," Durrheim said.
Is the industry goal of "zero harm" attainable?
"When you have over 5,000 men working at such depths and with so much heavy equipment and explosives and things like that it is very difficult to guarantee zero harm," Durrheim said.