The mining industry relies on blasting as a means of breaking rock, which means that mining is stopped for two to three hours a day to dissipate the toxic fumes and stabilize the rock mass after blasting.

The non-explosive rock breaking (NERB) research program in the Mandela mining area aims to find a solution to overcome this very inefficient mining method and find a mining method that allows zero dilution, zero risk, and zero downtime. CHANTELLE KOTZE wrote.

This article was first published in the 12th issue of the African Mining Review in 2019, please read the full text here or subscribe here to receive the printed version

The coral reef deposits in South Africa, especially those containing gold and platinum, are narrow and flat.

Although the law stipulates that the minimum operating height in areas where people work is 800 mm, the thickness of some narrow reef mines in the country is less than 500 mm, which leads to ore dilution because waste ore with zero economic value is also mined.

"The mining industry is the only major industry that uses this stop/start method and high dilution - the mining industry is a rock factory - we need to figure out more effective ways to break the rock and move the rock - but only what we want There is no risk to the rock and mine employees," commented Navensingh, director of the Mandela mining area.

The NERB project initially studied a total of six non-explosive rock fragmentation methods, including:

Among the six technologies initially identified and evaluated, studies have shown that there are currently no feasible technologies or solutions available for chemical, pore expansion, and electromagnetic methods.

Therefore, the focus is on the remaining three technologies, including mechanical cutting (dark drilling), heat (thermal spalling) and abrasives (diamond wire), all of which have been tested-the first two technologies are by AngloGold Ashanti and 1900 In the late 1980s, Anglo American Group conducted experiments on the latter technology in Welkom, Free State, South Africa.

As a result of the first year of the program, after evaluating the applicability of the three technologies based on a series of criteria, the industry representatives who oversaw the NERB program in the Mandela mining area approved what to be done in terms of hot spalling and diamond wire Further work cutting.

Hot spalling is a process in which rocks rupture and rupture due to changes in the temperature of a heat gun. It is working with MaXem, a provider of underground drilling and blasting solutions, to conduct further research in the NERB program.

MaXem is the South African distributor of Canadian Nippon's exclusive patented pyrolysis technology.

Singh explained that although thermal spalling has proven to be an effective method of breaking rocks, additional work will be required and will be completed on support tasks, such as clearing holes in flat impregnated ore bodies, which has been proven in the past. It is challenging.

The University of South Africa has developed a total of 12 cleaning solutions for impregnation and more challenging flat impregnated ore bodies. Three of the 12 selected solutions will be further investigated and tested on UG2 and Melensky Reef. The open-pit platinum mine owned by Sibanye-Stillwater, and possible future trials at Lonmin’s Baobab underground shaft in Limpopo (which has been acquired by Sibanye-Stillwater).

At the same time, a small test rig was built in the Mandela mining area to test the exfoliability of PGM rock samples using the hot exfoliation method. The results will be announced in March 2020.

Research on the best cleaning methods (including spiral suction, water extraction, and a combination of water and vacuum suction) is still ongoing.

Diamond wire cutting is a commonly used cutting method in quarries, especially for granite and marble. Over the years, diamond wire technology has also been improved.

In the case of underground mining, AngloGold Ashanti successfully used this technology in one of its deep gold mines, but the challenge was to overcome the high closure rate in the coral reef, which would cause the wire to get stuck on the overhang and the reef.

The results of the AngloGold Ashanti diamond wire cutting test prompted the Mandela mining area to consider the use of this technology in shallow platinum mines not exceeding 1,000 meters, where the closure rate is the lowest or even zero.

The current research project is studying the best mine layout of diamond wire cutting as a mining method. It is expected that by March 2020, the NERB research program will complete the financial evaluation of diamond wire cutting.

The NERB plan is currently studying the use of diamond wire cutting for column extraction, if the stress environment allows extraction.

This will see the extraction of pillars in the bord and pillar or room and pillar mining method as a means of extracting the coral reefs left behind by this mining method.

The current investigation will consider the pillar stress and the best extraction mode, the best way to support the pillar during and after extraction, and other parameters such as time and cost in order to develop the value proposition of pillar extraction using the following methods.

The focus of the NERB plan is still to promote the development of these three technologies through laboratory-scale trials and final prototype development, and then trials in operating mines. 

At the same time, the Mandela mining area is developing a mine design laboratory where various scenarios, simulations and economic models will be applied to new mining methods based on this extraction method to prove its feasibility.

“After a solution is found,” Singh emphasized, “then the South African mining industry will be able to use these new mining methods to unlock and reopen areas that were abandoned due to economic reasons or geotechnical issues as part of the revitalization of the mining industry. This way. At home. This creates more jobs in the mining and manufacturing industries to support these new mining methods.

 "The advantage of this is that we can mine more mines without having to sink new mines. Most importantly, we can now solve the problems of old mines and abandoned mines, which are currently burdening the environment and due to illegal mining. And flooding.

"For the future, this means that we can eliminate the need to set up tailings dams on the surface and further reduce the impact on the environment. It is vital that we will be able to mine safely without risking mine employees," Singh concluded.

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