24 November 2017

Reef Boring : Innovative Mining

12 February 2014

South African gold reserves form part of substantial supply of the world's gold supply. In 2002, SA constituted 15% of the world's gold production. This is a severe decline from the 30% mark that was experienced in 1993. Through innovation and advances in techniques, nations with a smaller ore deposit are managing to extract more of the metal from their deposits and slowly seceding SA as one of the world's leading producers of gold. Today, SA rates as the 6th producer of gold in SA due to the decline in safe working environments for the miners.

Gold mining uses different techniques in accordance to the depth of the ore deposit as well as the exposure to the elements. The rock is studied for its ore content as well as it mechanical and geological compositions. The mechanical structure of the rock is of grave importance as this determines the manner with which the metal will be extracted. A weaker rock structure requires that reinforcement be installed which can lead to a costly and unsafe environment for the miners. South African ore deposits required that drilling and blasting be the method of choice for the extraction of ore from the rock. This meant that cumbersome boring machines would bore tunnels, miners would then drill the rocks and blasting would then take place. The nature of these processes creates an uncontrolled environment due to the nature of blasting. Once an area is mined, packs are then inserted to support the structure and fill the voids created by the removal of ore. Where a rock face was incorrectly characterised, a weakening of the structure would be created which would then lead to rock falls and geological faults. This culminates into an unsafe environment for workers.

Manual drilling to enable insertion of dynamite into the core

It is with this in mind that industry is looking to leave the old drill and blast technique of old. It is in this respect that AngloGold Ashanti is making strides with its reef boring machines. This technique eliminates the need for packs to be installed once an area is mined. The technique requires that parallel tunnels are bored using tunnel boring machines and traverse to these tunnels, holes are drilled using the reef boring machines. These machines then punch out the gold containing reef. The holes are then filled by cement which hardens to rock strength within 21 days. The strength of this cement is rated at 170 megapascals, which is 5 times stronger than the concrete used in buildings and bridges. This relieves the structure of any geological and mechanical defects created by voids as well as completely removing the risk created should the packs fail.

This is a very practical and a well thought out manner of extracting gold from the land. Its aim is to make the working environment safer whilst increasing production within the shaft. In 2003, the mining industry experienced a total of 270 deaths related to mining activities. This number decreased dramatically in 2013 when only 29 deaths were reported for the same period. In 2003, the mining industry created and implemented a plan to reach a state of Zero Fatalities for the year 2013. This unfortunately was not reached due to the lack of enforcement by the Mine Health and Safety Inspectorate.

Compliance to the imperatives set at the 2003 summit

The truest effect of this technology will be felt when full scale commission is commenced. Current extraction methods can only extract 30 million of the 230 million ounces available in SA. As it stands, more than 50% of the mine running costs is attributed to labour costs as well as the costs of improving the safety rating of a mine. Previous strikes in the mining sector have exposed the level to which these costs are set to rise as the output of the mines are directly related to the labour input and effective use. AngloGold Ashanti aims to increase their output by between 10-20% using these machines. This, coupled with the current operating model will see rejuvenation in the industry that has since been stagnant due to rising labour and capital costs. A fear created within the industry by the appearance of these machines is that jobs would be lost within the labour intensive mining sector. Reports released by AngloGold show that labour will not be lost as the core activities of removing the rock still require manual labour. Furthermore, labour will be required to service the increased number of sections that will now be exposed due to the safer extraction methods availed by this technology.

"If we don't find a new mining method there will be no jobs in 30 years from now. This process creates jobs. You can't just switch off the labour-intensive drill-and-blast type mining we do now - Shaun Newberry, senior vice-president in charge of AngloGold's projects and technology division.

The underlying effect of this technology will be to create a sustainable long term mining model that will create more reserves as opposed to the current supply-demand model in use. This will allow businesses to predict future prices of the commodity as well as creating a reserve to sustain businesses during costly strikes.

"We will be able to open ore bodies that we are not mining because they're not viable. It will create a technical and financial model to convert more resources into reserves which means more mining over a longer period of time," The viability of the method is quite certain and its effectiveness can be seen clearly from the results under testing. The use of the technology will alleviate safety concerns industry wide as well as putting pressure on other companies to follow suit and find innovative ways to remain productive, sustainable and enhance the safe operational nature that the industry wants to foster.


Vhukhudo Nemanashi
vmnemanashi@gmail.com

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