Quote:
Going Deep
As the shallower and more accessible gold deposits were mined out, mining companies were forced to dig deeper and deeper. Some of the deepest mines in the world are found in South Africa, where gold is mined at depths up to four kilometers (2.4 miles). This presents a host of operational problems, such as ambient underground temperatures of 50 degrees Celsius or more, occasional rock bursts, groundwater seepage and ever present danger of flooding.
The logistics of mining at ultra-deep levels necessitated development of a raft of new technologies. These include sturdier cables, mammoth air refrigeration systems capable of cooling hundreds of kilometers of underground tunnels, and devices to detect seismic activity, allowing miners to be evacuated before a rock burst.
At the Beatrix Gold Mine in South AfricaOs Free State province, owned by Gencor, South Africa's second largest mining house, thousands of miners must be conveyed each day to working areas as deep as one kilometer beneath the surface. From there, they proceed along tunnels and Ûstopes,Ó exposing new gold-bearing rock seams for blasting and clearing. The blasted rock is conveyed to the central shaft by locomotive-driven hoppers, where it is hoisted to the surface for processing into raw gold.
A massive underground infrastructure is required to keep this mine functioning safely 24 hours a day. Huge surface fans blow refrigerated air through the latticework of tunnels below, keeping temperatures to a workable range between 17 and 29.5 Celsius. The mine comprises two shafts at depths of 960 meters and 912.5 meters, while a third shaft currently under construction will descend to nearly 1.5 kilometers (almost 1 mile). Tunnels radiate from the shafts at various depths. Scores of ÛdrivesÓ and stopes branch out from these tunnels, providing access to the gold-bearing seam, often just a few feet thick. As the gold is mined out, the tunnels and stopes stray farther from the shaft. The shaft is the lifeline of the mine, delivering men and materials to the working areas below - and gold-bearing ore to the surface, all by way of large lifts.
