Going Super Deep
The Zhelezny open pit mine in the Murmansk region is developing super deep mining, requiring extraordinary control of drilling and blasting on near vertical benches. In Russia it is described as a breakthrough technique and with the right equipment, the mine management is more than optimistic.
Mining company Kovdorsky GOK is confidently developing a ?super deep? mine at its Zhelezny open pit. As a result, the company, owned by the fertilizer giant Eurochem, will be able to gain access to an additional 300?400 millio¬n tonnes of ore and extend its life by a further 30 years, from 2015 to 2049.
Iron ore is the primary production at Zhelezny but the pit also produces valuable apatite which is used in the fertilizer industry as well as baddeleyite, a zirconium oxide, used in the industrial minerals sector.
The orebody is vertical and the pit measures 2.3 km in length, 1.7 km wide and is currently 170 m deep. It will eventually becom¬e 900 m deep without any significant enlargement of the pit rim.
According to the plan, the first target will be to maintain the ore output at 23 Mt/y until the year 2032, after which production will gradually decrease.
The entire project has been preceded by several years of highly advanced and extensive studies using some of the most sophisticated methods of testing, calculation and analysis in the industry.
From the results obtained it is clear that the project will depend heavily on the performance of the Atlas Copco drilling equipment at the site.There are two fleets involved, the first owned and operated by Kovdorsky GOK, the other by mining contractor Technobur. These include large-hole rotary drill rigs, down-the-hole crawlers and rock drilling tools from Secoroc.
It is also clear that extraordinarily careful drilling and blasting in order to maintain maximum stability of the 12?15 m high benches, is, and will continue to be, the key to success.
The studies resulted in a set of parameters for the engineering geologists and a 3D model of the deposit which was used to forecast areas where slopes might fail. Five different geological zones were selected for testing and for each one, the bench slope angles, heights and the required width of safety berms were defined.
This information led to a list of specifications for the excavation of the ?new? pit including extra-careful blasting techniques involving pre-splitting, relief of wate¬r pressur¬e in the benches, stabilization of weak rock masses using rock bolts and cement injection, as well constant slope stabilit¬y monitoring.
Epiroc operated under the trademark “Atlas Copco” prior to January 1, 2018.