c. 2020 pitt & sherry

Palabora Mining Company SRB1 and SRB2 Shaft Excavation

South Africa

The Palabora Copper Mine is an underground cave mining operation located in the Limpopo Province of South Africa. Mining is currently underway to set up the second lift of caving operations, a part of which involves the excavation of ventilation shafts from 1,200 m depth to surface.

Several potential locations for the shafts had been chosen and geotechnical drilling had been conducted. However, large faults were encountered in most areas. pitt&sherry was commissioned to re-evaluate the geotechnical assessments and propose an excavation strategy for the shafts. Ultimately a site was chosen where pre-support (semi-contiguous piles) down to approximately 20 m depth and raise-boring two 1,200 m long, 6.2 m diameter shafts to surface was recommended.

Because of the scale of the excavation, its importance to the project and the potential issues, pitt&sherry facilitated a detailed risk assessment workshop with all concerned parties. As a result, innovative risk mitigation techniques are to be employed in the excavation of the shafts. These include the close monitoring of shaft stability and development (by the raise-boring contractor) of a world-first system for the remote application of shotcrete at such depths. Raise-boring of the shafts is still ongoing.

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