The sinking of the 1,200-m deep ventilation shaft at Palabora Copper, in South Africa, is proceeding apace, notwithstanding the COVID-19 shutdown and restrictions, contractor Murray & Roberts Cementation reports.
Work began on the 8.5 m diameter shaft early in 2019, with pre-sinking recently reaching a depth of 50 m and the changeover from pre-sink to main sink almost complete, according to Murray & Roberts Cementation Project Executive Mine Development, Graham Chamberlain.
Part of the development of Palabora Copper’s new LIFT II underground block cave mining area, the shaft will be developed to a final blind sink depth of 1,190 m, with a drop raise to its final depth. Completion is expected in the September quarter of 2022, Murray & Roberts Cementation says.
“We were required by the client and national lockdown regulations to pause our work schedule, but operations resumed as planned when restrictions were relaxed,” Chamberlain said. “The priority is to ensure that safe working conditions are maintained, and the COVID-19 infections are avoided.”
The project is using automated machinery at the shaft bottom, removing employees from high-risk contact areas. Modern, high-penetration rate hydraulic drills are deployed on robotic arms nested on the shaft sinking stage. This allows operators to conduct drilling at any position in the shaft without physically being in contact with the drills, the company says.
“We shorten our cycle times with the use of explosive delivery pods containing sensitised emulsion,” Chamberlain said. “Electronic systems deliver real-time data on blast holes numbers, volumes and pressures, improving blasting efficiency and quality.”
To reduce potential disruption from the intersection of poor ground conditions, Murray & Roberts Cementation takes the shaft lining to the bottom of the shaft during sinking. In the past, industry practice tended to carry this lining to about 20 m from the bottom.
“Our lining approach is applied with the use of a modified version of the traditional shuttering, and our specialised concrete mixes which we design for this specific purpose,” Chamberlain explained. “The mixes are prepared and delivered by our on-site batch plant.”
Chamberlain adds that the company’s focus on Zero Harm and a rigorous safety regime continues to deliver a high level of safety on the project.