Modern Mining April 2016

COVER STORY

months in 2014 while Ivanplats awaited the formal execution of its 30-year mining right. Since then it has been all systems go with the main focus of activity being the 7,25 m inter- nal diameter, 975 m deep, concrete-lined No 1 shaft, one of the cornerstones of phase one. When Modern Mining was on site recently, the pre-sink had been completed to 54 m and the shaft-sinking contractor, Aveng Mining Shafts & Underground, was preparing for the slow sink stage (the preliminary to the main sink) with the 40 m high steel sinking headgear erected, the five-deck stage in position in the shaft and the final installation of the double-drum kibble winder and four-drum stage winder underway. According to Mouton, the shaft-sinking will employ tried and tested traditional methods using conventional jumbo drill rigs and cactus grabs. “We would expect Aveng to achieve an advance rate of 2,5 m a day once in full sink mode and at this stage we are anticipating inter- secting the Flatreef at a depth of 777 m in late 2017 with shaft bottom being reached in 2018,” he says. “Although Shaft 1 is designated as the primary ventilation intake shaft, we will be hoisting through it as it will be used for early underground development and this hoisting role might become permanent as we move into phase two.” He adds that development work will include three stations at depths of 450 m, 750 m and 850 m below surface. Shaft 1 is the smaller of the two main shafts required for the full implementation of the phase one Platreef project. The main pro- duction shaft will be Shaft 2, which – once completed – will rank as one of the biggest shafts in the platinum mining field in South Africa. Located just 100 m from Shaft 1, it will have an internal diameter of 10 m and be sunk to a depth of 1 250 m below surface. Capable of hoisting 6 Mt/a, it will be equipped with two high-speed 40-tonne skips running at 18 m/s and will also be capable of conveying 225 persons in a single deck using a cage and coun- ter-weight arrangement. At this stage, Ivanplats is expecting to start early works for Shaft 2 in 2017, including civils work for the boxcut and hitch foundation. The headgear of Shaft 2 will be an impos- ing concrete structure, 100,5 m high, making it similar in size to the concrete headframe of Impala’s No 16 shaft near Rustenburg. It will accommodate two Koepe winding sys- tems which will be positioned 82 m above ground and – at a lower elevation – a single drum auxiliary winder. The contract for the design of the headframe – now complete – was awarded to Murray & Roberts Cementation in

2014. Interestingly, the company has produced a 1:260 scale model of the headgear using 3D printing technology (see our photo), represent- ing its first use of this technology. The model was printed using ceramics as opposed to plas- tics for aesthetic purposes, with the printing process taking just 17 hours. One of the reasons for the generous dimen- sions of Shaft 2 is the fact that it will be used to transport large trackless equipment under- ground. Explains Mouton: “Based on the recommendations of the PFS, we’ll be using highly mechanised mining methods requiring the use of some very large mining equipment – for example, 40 and 50-tonne capacity min- ing trucks and 14 and 17-tonne LHDs. These machines will ‘live’ underground where we will have workshops initially but, of course, we have to get them down there in the first place and also occasionally bring them to surface for complete rebuilds. The dimensions of Shaft 2 will allow us to do this, although the bigger machines will still have to be broken down to allow them to fit within the cage.” Transverse longhole stoping on a retreat basis will the mining method applied to ore zones with vertical thicknesses greater than or equal to 18 m while thinner ore zones will be mined using mechanised drift-and-fill or drift- and-bench methods. Paste backfill will be used for post-mining support although in the first two years of production (prior to the startup of the mill and the paste backfill plant) cemented rock fill will be used as the fill system. Most of the cemented paste fill (CPF) preparation sys- tem will be located on surface with the only underground components being the pipeline distribution to the stopes. Commenting on the use of longhole stop- ing, Mouton says that the method – which is

The stage and bank steel be- ing lowered into Shaft 1.

“Although Shaft 1 is designated as the primary ventilation intake shaft, we will be hoisting through

it as it will be used for early underground

development and this hoisting role might become permanent as we move into phase two.”

April 2016  MODERN MINING  25