The geotechnical evolution of deep-level mechanized destress mining at South Deep mine

Abstract

The South Deep mine is a deep-level mine that is actively mining between 2600 m and 3000 m below surface, with expectations to mine to 3400 m depth. The The orebody lends itself to a fully mechanized mining method. The main geotechnical challenges for successfully mining the South Deep orebody were to destress and then cost-effectively extract the massive, low-grade orebody. Since Gold Fields acquired South Deep in 2007, several mining methods have been used to date, but destressing was done conventionally using traditional South African narrow-reef gold mining methods. In 2015, the mine moved to high-profile (5.5 m high) horizontal destress development with mechanized installation of ground support, and crush pillars were replaced with yield pillars. This has resulted in a safer working environment with industry best-practice support standards and less seismic energy release, while still allowing appropriate productivity rates This paper outlines the geotechnical processes used to overcome issues as they were encountered, including ground support, seismicity, and rock mass conditions, and highlights the key leanings of a deep-level massive mine's evolution over time.