Mine Access and Development

Mine Access and Development

• Underground mine access is vital for safe, efficient, and economical ore extraction. Access is categorized into primary (main), secondary (level/orebody), and tertiary (lateral/panel) openings.
• Primary openings, like shafts, adits, and declines/slopes, are crucial and must be carefully planned early in the mine life.
• Key decisions include type, number, shape, and dimensions of primary openings, which are greatly affected by:
  • Deposit size, shape, and depth
  • Surface terrain
  • Geology (orebody and surrounding rock)
  • Mining method and production rate
  • Climate
  • Infrastructure
  • Regulations
  • Environmental concerns
• Size of main openings is influenced by:
  • Ventilation needs
  • Daily tonnage hoisted
  • Mobile equipment size
  • Number of personnel
  • Required services (power, water, air).
• Primary openings can serve an explorative function, offering crucial information before full-scale mining. Exploration often precedes mining
• Underground mines are preferred when open-pit mining is uneconomical due to depth or when ore bodies were previously mined at surface.
• Raise Boring: A method for creating vertical or inclined shafts between levels. Access is required at both ends.
  • A pilot hole is initially drilled downwards using a raise boring machine.
  • The raise-boring machine is then used to ream the hole to the required diameter, rotating the reaming head upwards towards the fixed machine at the start of the pilot hole.
  • Cuttings fall to the lower level and are removed by safe methods (e.g., remote control).
  • Raise boring is advantageous due to capital cost (which is relatively high), but it has a good ROI for longer shafts. Other benefits include no miner presence during the excavation process, continuous operation, no explosives, smooth and stable profile, and reduced manpower. However, the most critical advantage is safety.
• Alimak Raising: An alternative to raise boring, safer than conventional raise development. Suitable for ore-passes, short raises, and short shafts, especially with only bottom access. Requires vertical or steep dipping excavations.
  • Developed in 1957 for high-rise building construction.
  • Applications include ventilation raises, stope slot raises (for longhole open stopes), ore/waste pass systems, raise bore rehabilitation, ventilation shafts, manway raises, and emergency ladder way installations.
  • Alimak Raise Climbers are available with air, electric, or diesel/hydraulic drive units. A 1,050m-long shaft was driven in one step in Norway.
  • Platforms can vary in shape and size, with the largest supplied exceeding 30m².
  • A movable working platform running on a monorail beam. Improves productivity and safety. The monorail track lengthens with sections added and bolted to excavation sidewalls.
  • Five production steps, using a raise climber:
    • Scale: Make safe area around personnel cage (with canopy).
    • Drill: From the drill deck on top of the climber, sized for the raise.
    • Charge: After drilling, charge the face with explosives.
    • Blast: Lower climber to the bottom, into a station for protection, before remotely triggering the blast. Rail remains protected.
    • Ventilate and remove: Effectively ventilate and remove broken ore from the excavation bottom, preparing for re-entry.

Explore the critical aspects of underground mine access and development in this quiz. Understand the importance of primary, secondary, and tertiary openings, and the key factors influencing their design and functionality. Test your knowledge on decision-making related to mine infrastructure and regulations.