Murray & Roberts Cementation reported the new ventilation shaft at Palabora Copper mine (PMC) passed the 800-m mark, which is two-thirds of the shaft’s planned depth of 1,200 m. According to Fred Durand, the company’s senior project manager, the shaft sinking is currently making good progress, with 40 or more lined m of advance being completed 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, PMC, taking place at the end of the first quarter of 2024,” he said.
Ground conditions have been challenging thus far, resulting in the shaft lining being taken right down to the blasted face, said Jas Malherbe, project manager. “Normally, we would line the shaft to within 12 to 18 m of shaft bottom and support the sidewalls temporarily with split sets and mesh,” he said.
“In practice, this did not prove viable, prompting us to change our approach,” Malherbe said. “The method we’ve adopted is unconventional but has proven to be highly effective.”
Two twin-boom Komatsu electro-hydraulic jumbo drill rigs are lowered down the shaft from surface and nested in the four-deck stage for drilling the shaft bottom, a procedure that is repeated for each 48-hour blast-to-blast cycle. Also, a Komatsu excavator with a 0.3-m3 bucket is lowered from surface through the stage to shaft bottom and is used for lashing.
So far, blasting has produced large rocks, which can be difficult to handle, Malherbe said. “We break these up using the excavator which has a quick coupler that allows it be fitted with a hydraulic breaker within a few minutes.”
All the waste rock is brought to the surface by an 11-metric ton (mt) kibble.
The methods used at Palabora are based on the Canadian shaft-sinking method that Murray & Roberts Cementation pioneered in South Africa at its Venetia mine project for De Beers Group.
“We have adapted the method because of the very different conditions we’re facing, but many elements remain the same or are very similar,” Malherbe said. “In particular, the high degree of safety offered by the Canadian method has not in any way been compromised.”
Murray & Roberts Cementation’s contract to sink the 8.5-m-dia. shaft was awarded in February 2019.
The ventilation shaft forms part of the copper producer’s Lift II project which will extend mine life by more than 15 years. Originally an open pit mine, the Palabora mine transitioned to an underground block cave operation in the early 2000s when Lift 1 was commissioned.
PMC is located within Phalaborwa in the Limpopo province in South Africa
