New drilling method boosts gold mining efficiency
A local drilling contractor based in South Africa may have developed an alternate gold mining process, dramatically increasing the efficiency of current mining practices. The method was discovered in 1974 but development of it lost traction and was eventually abandoned after failing to find investment.
The decline in South African gold production has become an increasing problem over the past 10 years, the depth at which the gold is buried makes it difficult to extract. Blasting at such immense depths damages ground conditions and also creates seismicity, a looming catalyst for mine cave ins; because of this shaft pillars are used to ensure stability. Unfortunately shaft pillars lock up a significant amount of the precious metal, making the extraction of it all but impossible.
The new method of drilling proves significantly safer both to the seismic stability and to the workers, as the traditional blasting method is abandoned. Currently for an often significant time period after blasting a mine cannot be entered due to the level of dust and consequent low visibility; this creates dead time during which work is suspended and productivity plummets.
The new method allows for constant gold mining with an increased gold take. The process uses conventional rasie-bore equipment to drill 26 meters from one sublevel to another at a 26 degree angle. Previously the idea of drilling from one sub level to another had not properly been explored or appreciated. The method is being tested by AngloGold whose executive VP Mike Macfarlane is excited by the technical advancement and can see its potential to drill further still.
The AngloGold Ashanti team has almost completed the new mine design using this method and a ‘harder-than-concrete’ backfill of up to 100 MPa (a stabilization method to ensure the mines structural rigidity) is en-route.
The team is prototyping a series of other mining projects such as reverse-circulation drilling, which involves threading a camera through the hole to locate and capture the environment. The data collected is then processed and used to produce a 3D model of the reef. The success rate of this process has been impressive as the resolution captured by the camera has been higher than was initially expected.
AngloGold says 2012 and 2013 will continue to be years dedicated to prototyping, finding the most cost effective, sustainable, and lucrative method to bore and extract as much gold as possible.
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