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Block Caving Instead of Open Pit
Mining – A way to decrease waste rock
production
Mahdi Shabanimashcool
Associate professor in Rock Mechanics and Mining
UiT – Narvik
Mining Education in Narvik
• Started since 2013• 4 graduated in 2014• 8 is going to graduate 2016• ---
Projects• New coal products in corporation with
SNSK, 2013 to 2014• Smart Mining Technology, 2015 to 2016.
Mining – Supply and Demand
Mineral Processing ConcentrateGangue
Terminology
Block Caving
https://www.youtube.com/watch?v=wb9RPgs7oAQ
Production in surface and underground mines
Har
tman
& M
utm
ansk
y2
00
6.
Waste to Ore tonnage
Ore and waste production in surface and underground mines, USA.
Har
tman
& M
utm
ansk
y2
00
6.
Overall stripping ratio for surface mining : 2 to 12Overall stripping ratio for underground mines: 0 to 0.1
Mining Method selection
Factors to determine mining methods:
• Spatial characteristics of the deposit• Geologic and hydrologic conditions • Geotechnical properties • Economical factors • Environmental concerns
Mining Method selection
Hartman & Mutmansky 2006.
Mining method selection
Characteristics Open Pit Block Caving
Production rate Large-scale Large-scale
Productivity High High
Capital investment Large Large
Development rate Rapid Slow
Depth capacity Limited Moderate
Selectivity Low Low
Recovery High High
Dilution Moderate Moderate
Flexibility Moderate Low
Stability of openings High Moderate
Environmental risks High High
Water disposal Extensive Moderate
Health and safety Good Good
Mining method selection
Capital and operation costs for open pit and caving mines, Australia
Mining method selection – Deposit condition
Factor Open Pit Block Caving
Ore strength Any Weak to Moderate, Cavable
Rock Strength Any Weak to Moderate, Cavable
Deposit shape Massive, pref. tabular Massive, tabular
Deposit dip Any Fairly steep
Deposit size Large, thick Large, thick
Ore grade Low Low
Ore uniformity Uniform Uniform to fairly uniform
Depth Shallow to moderate Moderate
Block Caving
Block Caving
𝑁 = 𝑄 × 𝐴 × 𝐵 × 𝐶
Fragmentation
Primary fragmentation: In situ block size
Secondary:
• Extension of pre-existing discontinuities
• Opening of filled and healed discontinuities
• Opening along bedding or schistocity planes
• Crushing under superimposed weight
• Failure of blocks under arching stress
• Abrasion of block corners
Artificial fragmentation – Shaped charges
M. Shabanimashcool 19
Artificial fragmentation – Shaped charges
Artificial fragmentation – Shaped charges
Avoid the intensive pulverization
Use the pressure efficiently before it vents to atmosphere
Subsidence
Subsidence
Subsidence control
Conclusions and Recommendations
• Block caving instead of open pit mining • Waste rock production is eliminated • Better drilling technique, example from LKAB• Shaped charge and guided fragmentation • Pre-fracturing and controlling of subsidence • Better site investigations and ore modelling technique • Trying an experimental case
• Big demand for R&D programs • 70% of solution is technical not political
