The efficiency of mechanical rock breaking underground is not determined by a single method but depends on a complex interplay of rock mass properties, excavation design, economic factors, and safety and environmental constraints (Epiroc, 2020). No single method is universally most efficient; the optimal choice requires a site-specific assessment.
Key mechanical methods and their efficiencies include:
- Hydraulic Impact Hammers/Breakers: These offer high flexibility and lower capital costs, suitable for secondary breaking, scaling, and primary excavation in softer or fractured rock, or where blasting is restricted. Their efficiency in hard rock primary excavation is limited, with operational costs rising due to tool wear and energy consumption (Epiroc, 2020).
- Rotary Drum Cutters (Roadheaders, Rockwheels):
- Roadheaders: These are efficient for excavating various profiles in soft to medium-strength rock (typically UCS < 120 MPa, up to 160 MPa in favorable conditions). They offer good flexibility and produce smoother profiles than blasting (MDPI, 2019).
- Rockwheels: Excavator-mounted attachments that provide precise cutting with low noise and vibration, suitable for soft to medium-hard rock and sensitive areas. They can be more productive than hydraulic hammers in suitable conditions and produce reusable material (RockZone Americas, n.d).
- Tunnel Boring Machines (TBMs): TBMs offer the highest advance rates for long, straight tunnels in a wide range of ground conditions, from soft ground to very hard rock (The Robbins Company, n.d.). They are most efficient for large-scale projects where their high capital and mobilization costs can be amortized (The Robbins Company, n.d.).
- Hydraulic Rock Splitters: Efficient for controlled, precise breaking in sensitive areas or for oversized boulders, with minimal environmental impact, but not suited for bulk excavation (GMD Large Rock Splitter, 2024).
Selecting the “most efficient” method involves a systematic approach: comprehensive geotechnical investigation, defining project objectives and constraints, preliminary method screening, detailed comparative evaluation (including production rates, operational costs, flexibility, and stability impacts), and risk assessment (Epiroc, 2020).
Which factors do you think matter most when choosing the best rock-breaking method underground: rock type, cost, or safety? Share your thoughts!
References:
Epiroc. (2020). Underground. Mechanical rock excavation equipment. https://www.epiroc.com/content/dam/epiroc/hydraulic-attachment-tools/brochures/en/Epiroc_Underground_Leaflet_9864010101.pdf
GMD Large Rock Splitter. (2024, March 13). Working Principle Of Hydraulic Rock Splitter. https://www.gmd-eqpt.com/info/working-principle-of-hydraulic-rock-splitter-93380703.html
MDPI. (2019, September 17). Methods of Mechanical Mining of Compact-Rock—A Comparison of Efficiency and Energy Consumption. https://www.mdpi.com/1996-1073/12/18/3562
RockZone Americas. (n.d.). Excavation Equipment for Precise Rock & Concrete Cutting. https://rockzoneamericas.com/applications/excavation
The Robbins Company. (n.d.). TBMs in Mining. https://www.robbinstbm.com/about/advancements/tbms-in-mining/
