Underground Mining Methods
by Dr. Arcady Dyskin & Mr. Paul Duplancic
A.V. Dyskin, UWA UWA
Learning objectives Basic
mining methods within the classification
Basic
principles of selection of the mining method
A.V. Dyskin, UWA UWA
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Underground Mining Methods
Schematic layout underground mine (Brady & Brown, 1993). A.V. Dyskin, UWA UWA
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Mining Terminology Deposit
and Spatial Terms
Excavation
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Terms
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Deposit and Spatial Terms • Back: roof, top or overlying surface of an underground excavation. • Country rock : waste material adjacent to a mineral deposit; also host rock. • Crown pillar: portion of the deposit overlying an excavation and left in place as a pillar • Footwall wall: rock under the deposit • Hanging wall: wall rock above a deposit • to the roof or hanging wall. • Rib: Side wall of an excavation; also rib pillar • Sill pillar: portion of the deposit underlying an excavation and left in place as a pillar A.V. Dyskin, UWA UWA
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Excavation Terms • Adit: Main horizontal or near-horizontal underground opening, with single access to surface • Decline: Inclined opening driven downward to connect levels; also declined s a t an ramp • Drawpoint: Loading point beneath a stope, utilizing gravity to move bulk material downward and into a conveyance, by a chute or LHD (Load-HaulDump vehicle) • Drift: Horizontal or near horizontal opening; also drive, entry • Incline: Inclined opening driven upward to connect levels • Level: System of horizontal openings connected to a shaft; comprises an • Orepass: Vertical or near-vertical opening through which bulk material flows by gravity • Portal: Opening or connection to the surface from an underground excavation • Raise: Vertical or near-vertical opening driven upward from one level to another A.V. Dyskin, UWA UWA
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Excavation Terms (Cont) • Room: Horizontal exploitation opening, usually in a bedded deposit • Shaft: Primary vertical or near-vertical opening connecting the surface with underground workings • Slot: Narrow vertical or inclined opening excavated in a deposit at the end of a stope to provide a bench face • Stope: Large exploitation opening, usually inclined or vertical • Sublevel: secondary or intermediate level between main levels or horizons • Transfer point: Location in the materials-handling system, either haulage or hoisting, where bulk material is transferred between conveyances • Tunnel: Main horizontal or near-horizontal opening, with access to the surface at both ends • Undercut: Low horizontal opening excavated under a portion of a deposit, usually a stope, to induce breakage and caving of the deposit • Winze: Vertical or near vertical opening driven downward from one level to another
A.V. Dyskin, UWA UWA
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A more insightful representation...
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I. Naturally Supported Methods A mining method based on natural support seeks to control the rock mass displacements through the zone of influence of mining, while mining proceeds. This implies maintenance of the local stability of thee ro th rock ck ar arou ound nd in indi divi vidu dual al ex exca cava vati tion onss an and d more general control of displacements in the near-field domain (Brady & Brown 1993). A.V. Dyskin, UWA UWA
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Room and Pillar
(Bord and Pillar mining in the coal industry) A.V. Dyskin, UWA UWA
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Room and Pillar Mining (2)
A.V. Dyskin, UWA UWA
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Conditions Host
rock strength: moderate to strong
Deposit
shape: tabular
Deposit
dip: low (<15 degrees), preferably
Depos Deposit it
size: large large extent extent – not thick thick
Ore
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grade: moderate Slide 12
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Features
Generally low recovery of resource as pillars need to be left (4060%)
Recovery can be improved with pillar extraction (60-80%) but caving and subsidence will occur
Suitable for total mechanisation, not labour intensive
High capital cost associated with mechanisation
Versatile for variety of roof conditions
Applications • Bord and pillar – Coal mining region of Ipswich, Queensland • Room and pillar pillar mining mining – MacA MacArther rther River River – North Queensla Queensland nd • Variation: Stope and pillar mining
A.V. Dyskin, UWA UWA
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Sublevel Stoping
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Sublevel Stoping (2)
A.V. Dyskin, UWA UWA
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Conditions Ore
strength: moderate to strong
Ho Host st
rock roc k stre stren n th th:: stro stron n
Deposit
shape: tabular or lenticular, regular dip and defined boundaries
Deposit
dip: steep (>45-50 degrees, preferably 60-90 degrees)
Deposit
size: 6-30m wide, fairly large
extent Ore A.V. Dyskin, UWA UWA
grade: moderate Slide 16
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Features Moderate Not
to high production rate
labour intensive labour intensive – can be mechanised mechanised
Low
breakage and handling cost
Inflexible
and non-selective non-selective (Recovery ~70%, dilution ~ 20%)
High
development costs
Limited
exposure to unsafe working conditions
Applications
• Mt Isa Mines, Queensland A.V. Dyskin, UWA UWA
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II. Artificially Supported Excavations to control local stope wall behaviour and mine near-field displacements: • Support is provided through devices such as rock-bolts, cable-bolts or grouted tendons. • Support is provided through an artificial support medium known as backfill.
A.V. Dyskin, UWA UWA
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Cut-and-Fill Stoping
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Conditions Ore
strength: moderate to strong
Ho Host st
rock ro ck st stre ren n th th:: wea weak k to to fai fairl rl we weak ak
Deposit
shape: tabular, can be irregular, discontinuous
Deposit
dip: steep(>45-50 degrees) can accommodate flatter deposits
Deposit Ore
size: 2-30m wide, fairly large extent
grade: fairly high
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Features Low
development cost
High
mining cost, due to backfilling operations
Permits
good selectivity, is versatile, flexible and adaptable
Backfilling Labour
can disrupt mining operation
intensive
Applications
• Mt Isa Mines, Queensland
A.V. Dyskin, UWA UWA
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Shrinkage Stoping
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Conditions Ore
strength: strong (other characteristics important impor tant – shoul should d not pack, oxidise oxidise or spon aneous y co com us
Host
rock strength: strong to fairly strong
Deposit
shape: tabular or lenticular, defined boundaries repose)
Deposi Depositt Ore
size: 1-30m 1-30m wide – fairl fairly y large extent extent
grade: fairly high
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Features
Suited to smaller scale operations –moderately low production ,
Low capital investment
Moderately selective
Majority of ore tied up in the stope
Ore subject to oxidation, packing and spontaneous combustion in stope
Applications • Limited modern modern use – was used at Broken Hill Hill
Variations: Vertical Crater Retreat
A.V. Dyskin, UWA UWA
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III. Unsupported Mining Methods distinguished from other mining methods by the fact that that near-field rock undergoes large displacements so that mined voids become self filling. In caving methods the far-field rock may also undergo large displacements (Brady & Brown, 1993).
A.V. Dyskin, UWA UWA
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Longwall Mining (1)
A.V. Dyskin, UWA UWA
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Longwall Mining (2)
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Longwall Mining (3)
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Conditions Ore
strength: any, preferably weak and can be cut by continuous miner
Host
rock strength: weak to moderate strength, must break and cave, floor must be non plastic
Deposit
shape: tabular
Deposit
dip: low (<12 degrees)
Deposit
size: large extent, thin bedded and of uniform thickness
Ore
grade: moderate and uniform
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Features
Extremely high productivity, low labour requirements
Low mining cost, high capital cost
Highly mechanised
Method inflexible and rigid in layout and execution, no selectivity
Surface subsidence will occur
A
lications
• Used in both coal and hardrock mines • Coal - Gordonstone, Oakey Oakey Creek and and German Creek, Creek, Bowen Basin Central Queensland. • Metaliferous – most deep level gold mines. mines. A.V. Dyskin, UWA UWA
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Sublevel Caving
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Conditions Ore
strength: moderate to fairly strong, should competent to stand without support
Host
rock strength: weak to strong, should be cavable.
Deposit
shape: tabular or massive
Deposit
dip: steep(>60 degrees), can be flat if the deposit is fairly thick.
Deposit Ore
size: large, extensive vertically
grade: moderate
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Features
High production rate, large scale method
High recovery, high dilution
Suitable for full mechanization
Caving and subsidence occurs
Draw control important
High development costs
Applications • Kiirunavaara iron ore mine, Kiruna, Sweden
Variations: Top slicing
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Block Caving
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Conditions Ore
strength: weak to strong, must be fractured or jointed and cave freely
Host
rock strength: weak-moderate, similar to ore in characteristics
Deposit
shape: massive or thick tabular, fairly
regular Deposit
dip: steep(>60 steep(>60 degrees degrees or vertical)
Deposit
size: very large
Ore
grade: low, uniform
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Features
High productivity, low mining cost (comparable to open pit mining)
Lar e scale method hi h roduction rates
High recovery and potentially high dilution
Rock breakage breakage by caving – no blasting costs costs
Large scale caving and subsidence, wholesale damage to surface
Good draw control essential
Slow, extensive and costly development
Highly mechanised
Inflexible
Applications • Northparkes mine, Central NSW, El teniete, Chile
A.V. Dyskin, UWA UWA
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Conclusions deposit is a function of • orebody geometry • size • geomechanical setting • orebody value and spatial distribution • engineering environment
A.V. Dyskin, UWA UWA
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