South Deep gold mine - Mining

3D schematic illustration of the South Deep gold mine
Mining methods

Current production is sourced from two primary mining areas, Current Mine (CM) and North of Wrench (NoW). CM is characterised by selective mining methods scattered over a large area whereas the NoW area focuses on six corridors migrating southwards with bulk non-selective mining methods.

The CM area is defined by the previously conventionally mined area that serves as destress for mechanised massive mining above and below these horizons in the remaining Elsburg reefs. Mining activities are largely scattered over the whole of the CM area. These areas are accessed with normal development from existing ramps and extracted with drifts, benches and long-hole stopes. Due to the nature of mining here and risks associated with mining between other old excavations, the resource to reserve conversion is generally low, however, feasible mining and extraction methods have the potential to mine these areas, and will be further assessed and developed where appropriate.

The NoW area is largely unmined, and an improved mining method is applied here designed for the efficient extraction of the thick ore body without being impacted by historical excavations, backfilled areas or old pillars. Applying an optimal bulk extraction method here maximises the gold ounce extraction and reduces mining complexity. Owing to South Deep's depth, a destress cut is required to lower the in-situ stress, such that mechanised bulk mining can be conducted. This cut also serves as access for bulk long-hole stoping. The 5.5 metre high destress cut is mined horizontally into the ore body with mechanised equipment similar to a room and pillar layout. From the destress cut, a long-hole stoping method is applied to extract the remainder of the Elsburg reefs to the cut above or the limit of the target zone. Thinner target areas for stoping above and below the destress cuts are mined with drifts and benches similar to CM. The combination of these methods, applied in NoW, significantly improves the resource to reserve conversion rate and forms the basis of South Deep's future.

All stoping areas are backfilled after completion to increase geotechnical stability of surrounding rock mass.

Mine planning and scheduling

Geotechnical consideration and interdependent activity cycles dictate the sequence and geometry in which South Deep can advance its mining activities. Detailed planning and sequencing of the combined development and destress access activities is required prior to commencing stoping. These critical path activities are resourced and scheduled to ensure that sufficient stoping areas are made available at the right time with a level of flexibility, to support the production build-up programme. Mining equipment and activity efficiency estimates were adjusted to be aligned with current performance. Improvements in efficiency over time are based on design enhancements and enablers that include:

  • Dual access to the working faces allowing for a smoother flow of equipment and improved fleet logistics
  • Satellite workshops on every cut to improve fleet maintenance, reliability and performance
  • Additional ore-passes per cut that will remove dump trucks from the stoping horizon
Mining sequence diagram

Innovation and technology (I&T)

South Deep will initiate I&T technical solutions, by implementing and trialling for further expansion, across the mine:

  • A new mine management system will collect live production data, including the spatial location of equipment, enabling real-time production reporting and short interval management control
  • An integrated 3D spatial data base in mine technical services integrating activities and creating seamless workflows
  • Deployment of tele-remote capabilities to remove employees from potential hazards and improve equipment effectiveness and productivity