Overview
This lecture explains the block caving mining method, detailing its process, requirements, and operational considerations for extracting large ore bodies efficiently.
Block Caving Process
- Block caving enables efficient extraction of large volumes of rock but has a longer development time before production begins.
- The process relies on drawing rock from a lower extraction level, creating a gap that causes the overlying rock to cave due to gravity and rock stress.
- Drilling and blasting of ore are minimized, but the ore body must be large and the rock conditions suitable for natural breakage.
- An undercut level is first developed and blasted to initiate caving in the lower part of the ore body.
- Below the undercut, an extraction level is constructed for ore removal throughout the production phase.
- Draw bells are formed between the undercut and extraction levels to channel caved rock downward.
Safety and Operational Considerations
- Accurate drilling is essential to avoid misfires during undercut development.
- Significant rock reinforcement is necessary, using steel arches, sprayed concrete, cable bolts, rock bolts, steel mesh, and straps.
- Reinforcement is required due to extreme rock stress changes and an extended production timeframe.
Ore Handling and Transport
- Ore is loaded from draw points and moved to ore passes connected to a haulage level or directly to a crusher.
- Various transportation methods may be used, depending on ore fragmentation and crushing needs.
Advantages and Impacts
- Block caving offers high productivity, low operating costs, and supports mechanization and automation.
- Ore extraction eventually leads to surface subsidence as surrounding rock caves in.
- Effective block caving depends on successful rock breakage and even ore extraction across draw points.
Key Terms & Definitions
- Block Caving — A large-scale underground mining method that causes rock to collapse under its weight for ore extraction.
- Undercut Level — The initial mined level where blasting breaks the base of the ore body to start caving.
- Extraction Level — The level where ore is collected during mine production.
- Draw Bells — Passages connecting the undercut and extraction levels, allowing caved rock to flow through.
- Subsidence — The sinking or settling of the ground surface due to underground mining.
Action Items / Next Steps
- Review block caving diagrams and process flow in the assigned reading.
- Study reinforcement techniques used in underground mining.