Mining contractor Murray & Roberts (M&R) Cementation’s shaft sinking team, responsible for sinking a new ventilation shaft at the Palabora copper mine, in Phalaborwa, Limpopo, have celebrated reaching a depth of 800 m – two-thirds of the shaft’s final depth of 1 200 m.
The ventilation shaft forms part of the copper mine’s Lift II project, which will extend the life-of-mine (LoM) by more than 15 years.
Originally an openpit mine, the Palabora mine transitioned to being an underground block cave operation in the early 2000s when Lift I was commissioned.
The extension of the LoM is expected to increase the mine’s value and continue sustaining livelihoods in the surrounding communities.
M&R Cementation’s contract to sink the 8.5-m-diameter shaft was awarded in February 2019. Senior project manager Fred Durand says the shaft sinking is making good progress, with at least 40 m of progress being made on average each month.
“Shaft sinking operations should be completed by the end of this year with final handover of the shaft to our client . . . at the end of the first quarter of 2024,” he says.
Ground conditions have presented a challenge on the project, which resulted in the shaft lining being taken right down to the blasted face, M&R Cementation on-site project manager Jas Malherbe reports.
“Normally, we would line the shaft to within 12 m to 18 m of shaft bottom and support the sidewalls temporarily with split sets and mesh. In practice, this did not prove viable, prompting us to change our approach. The method we’ve adopted is unconventional but has proven to be highly effective,” he explains.
Drilling is being carried out by two twin-boom Komatsu electro-hydraulic jumbo drill rigs. These are slung down the shaft from surface and nested in the four-deck stage for drilling the shaft bottom, a procedure which is repeated for each 48-hour blast-to-blast cycle.
Another key piece of equipment is a Komatsu excavator with a 0.3 m3 bucket. It is lowered from surface through the stage to shaft bottom and is used for lashing. All the waste rock is loaded into an 11 t kibble, which transports it to surface.
The ground conditions at the shaft are such that blasting tends to produce large rocks, which can be difficult to handle.
“We break these up using the excavator, which has a quick coupler which allows it to be fitted with a hydraulic breaker within a few minutes,” Malherbe says.
The methods being used at Palabora are based on the Canadian shaft-sinking method that M&R Cementation has pioneered in South Africa at its Venetia mine contract for diamond mining company De Beers.
“We have adapted the method because of the very different conditions we’re facing but many elements remain the same or are very similar. In particular, the high degree of safety offered by the Canadian method has not in any way been compromised,” Malherbe says.
The number of M&R Cementation personnel deployed per shift is 25. The total labour complement on site is currently just over 120 people, with 46% of them being recruited from local communities.
M&R Cementation’s corporate social investment programme is being run in conjunction with its contract. The programme is being implemented in close association with the Palabora copper mine and has mainly focused on supporting local schools in the Phalaborwa area with infrastructure such as ablution facilities, fences, water storage tanks and boreholes.
“In addition, we have trained nearly 80 youths from local communities at our Bentley Park Training Academy near Carletonville. Another 20 are currently undergoing training. This programme is giving them skills which are in high demand in mining and which could lead to them securing permanent employment within the mining industry,” Durand says.