Gold mining technology
The application of mining technology in South African gold mining has two main aims: to assist the industry and its employees to work safely and to work efficiently.
A great deal of attention is currently being focused by gold mining companies on the development of processes and technologies that will remove – as far as possible – individuals from the rockface, in order to minimise the threat of injury. This technology includes remotely-controlled machines to mine narrow veins. Such equipment is currently being tested.
DRILLING, BLASTING AND HAULING
Hydro-powered rock drills are faster and quieter than conventional drills powered by compressed air. Drillers spend less time at the rock face. In development ends, wholly-mechanised drills can do the hard work.
New water-based emulsions can be loaded quickly and safely into blast holes, to be detonated electronically from surface.
Trains that haul broken rock are operated by an electronic control system which incorporates remote sensing.
SEISMIC MONITORING AND RESEARCH
Seismicity occurs in the natural environment as the earth's continental plates continually move but is intensified by deep-level mining. A seismic event in the mining context is known as a rockburst. As the depth of mining increases, the stresses from the overhead rock mass intensify. Mining also causes stresses in these rock masses leading to a build-up of energy and then drastic release.
All seismic activity in South Africa is monitored and recorded by the Council for Geoscience, which is part of a global seismic monitoring network. In the past 20 years, the South African gold mining industry has spent more than R150 million on research, resulting in a greater understanding of seismicity, which has led to better ways of mitigating and avoiding incidents. Many mines now have comprehensive monitoring networks in place.
ICE PLANTS UNDERGROUND
Virgin rock temperatures can reach up to 60ºC at the depths mined in the South African gold mining industry. Sophisticated cooling methods and equipment, involving some of the largest refrigeration plants in the world, use ice and chilled water to reduce ambient temperatures to reasonable working temperatures.
Eight of the 10 deepest mines in the world are gold mines in South Africa. AngloGold Ashanti's Mponeng gold mine, located southwest of Johannesburg, is currently the deepest mine in the world. It extends over four kilometres below the surface.
Sinking shafts – or excavating a vertical or near-vertical tunnel from the top down – to such depths to access orebodies requires extraordinary expertise and knowledge. Shaft sinking is one of the most difficult of all development methods: restricted space, gravity, groundwater and specialised procedures make the task quite formidable.
Where the shaft is to be used for hoisting it is frequently split into multiple compartments. The largest compartment is typically used for the mine cage, a conveyance used for moving workers and supplies below the surface, which is suspended from the hoist on steel wire rope. Steel wire rope is a type of cable that gets its strength and durability from its helix design, which is achieved by twisting several strands of metal wire together. While a metal strand may deteriorate, the load will still be supported by the other strands in the cable. Wire ropes therefore provide greater peace of mind and additional safety when handling a heavy load.
Smoke inhalation may occur when there is an underground fire and the ventilation infrastructure is unable to clear the working areas. All employees have at their disposal self-contained self-rescue equipment – essentially a breathing apparatus that can be donned and which provides at least 30 minutes of oxygen, while the individual makes his/her way to a place of refuge. All underground working places are also equipped with refuge bays, which are protected chambers located within 30-minutes of all working places, and which are equipped with fresh air, water and communication devices.