As South Africa expands renewable energy and grid infrastructure across Mpumalangas coalfields, transmission planners and developers increasingly face a difficult engineering problem: how to design powerline pylons on ground affected by historic or active underground mining. A new technical paper presented at CIGRE Southern Africa 2025 on October 15 proposes a practical, risk-based methodology to assess these geotechnical hazards early in the design process, helping prevent costly failures and project delays.
The study, authored by ENERTRAG, Jones Wagener and RKS Innovation, highlights that subsidence and ground tilt remain two of the most significant risks for overhead line infrastructure in the Highveld region. Underground mining, particularly bord-and-pillar workings and high-extraction methods such as longwall or stoping, can create voids that deform over time. These deformations can compromise tower foundations, alter ground clearances, induce differential settlement or misalign conductors all with major implications for safety, reliability and power transfer capability.
According to the paper, different mining methods produce distinct surface effects: