Underground Mining Methods

Two Main Methods
- Room and Pillar

• Mostly with continuous miners

- Longwall – Develop longwall panels with room and pillar using continuous miners

- About 10% of underground production

• still comes from drilling and blasting

- Total underground output = 421mt (1997 data)

FIRST, MUST ACCESS THE MINE

- Drift (Adit)

• Seam outcrops, access from ground level

- Slope

• Drive incline in rock at up to 16 degrees
• Allows belt haulage

- Shaft

• Use: elevators/skips, for: people/coal
• Use shaft if >1500 feet, economics dictate

LIKE A CITY, OR LARGE BUILDING, SERVICES MUST BE PROVIDED

• Transport people (rail, rubber tired) - Transport supplies (materials / maintenance)
• Transport product (coal)
• Support roof
• Provide electrical power
• Provide fresh air (& suppress dust)
• Provide fresh water
• Get rid of waste water
• Dispose of trash

ROOM And PILLAR

• Mine “streets & avenues” (entries and crosscuts)
• Leave pillars to support roof (may mine later)

– Designed by formula

• Plan view-looks like city with “greenbelts”

– “Greenbelts” are large barrier pillars left to separate work areas

• Use continuous miner

MINE PLAN

• Main entries (7-9 openings)
• Submains (5-7 openings)
• Panels (panel entries, butt entries)
• Rooms (at times)
• Openings limited to 20-ft width

– Openings serve as air ducts and travelways – Return air is isolated from fresh air, two escapeways must be provided from face

• Longwall panels are solid coal blocks, usually 1000 ft by 10,000 ft, accessed by “gate” roads

ALL SERVICES EXIST TO SUPPORT MINING AT FACE
Continuous miner

- rips coal, using tungsten carbide bits

- miner mines at 4-25 t/m and conveys coal into shuttle cars

• Shuttle cars are electric (cable) “trucks” which haul for up to 600 feet or so (usual = 300-400 feet)

– Haul to feeder-breaker which acts as surge bin/crusher and feed coal onto belt

– Hold 3-25 tons/load, depending on seam thicknesss and amount of rock mined

FEEDER-BREAKER FEEDS COAL ONTO BELT CONVEYORS

• Conveyors transport coal to surface or into skips for shaft access

– Usual sizes - 42” to 72”

– Speeds - 500 - 800 fpm

• Longwall requires largest conveyors

– 54”-60” usual from face

ROOF BOLTS INSTALLED BY ROOF BOLTING MACHINE

• Roof supported by inserting reinforcing rods
• No one may work under unsupported roof – Cut depths limited to position of shuttle car operator (35’ to 40’ with remote control miner)
• When miner place changes, bolter moves in

– Bolt 3-6 min/row or 0.75-1.50 min/ft

– Use two bolter operators, twin-boom bolter

• A few operations attach bolters to miners, bolt as they advance

ROOF SUPPORT

• Insert bolts into the roof on regular pattern (3’-8’ length, usually)

– 4’ x 4’ or 5’ x 5’ most common

• Either “glue” (resin) a re-bar bolt in, or
• Use expansion bolt anchors or � Glue in the anchor only

– Anchors allow pre-tensioning of bolts

ROOF BOLTS GENERALLY WORK WELL

• Form “reinforced” rock, strong beam
• Or, may “hang” weak rock from stronger overlying rock layer
• Roof fall fatalities are now at 8 -12 per year

– Half are in violation of the law, under non-bolted roof

– Roof fall fatalities exceeded 100 per year around 1970

VENTILATION

• Provides oxygen, dilutes methane & dust

– Methane explosive when at 5-15% concentration Most coninuous miners have dust scrubber

– Draw air into ducts at front of miner

– Efficiency up to 96-97%

• Air directed to working face with brattice cloth (plastic curtains)
• Alternatively, hang tubing & use fan to draw air to face
• Fresh air ventilates one face only, then it is “return” air

– Separate air streams with concrete block walls or “stoppings”

• Maximum allowable methane content is 1%
• Control major flow with adjustable doors in airways (“regulators”)
• 150 - 400 ft/shift usual, tonnage depends on seam thickness

– 500 - 2000 tons/shift (usual)

• New miners load at 10 - 25 tpm
• Most continuous miners load only 60-120 min/shift

– Load only 12

– 10-25% of shift time

LONGWALL

• More nearly continuous method
• Analogous to “deli meat slicer” (shearer)
• Shearer mounted on chain conveyor
• – Coal cut falls onto conveyor
• Width of face usually 850 - 1100 ft
• – Depth of slice is 30 - 42 inches
• Behind face supported for 20’ or so by steel supports
• - each 1.50 or 1.75 m wide
• – Each support holds up to 600-1200 tons
• Supports connected to conveyor – By pushing, lowering & pulling
• - can walk conveyor and selves forward
• Panels (solid block of coal)
• – Usually 850’ - 1100’ wide & 7500’ - 15,000’ long
• – Contain 1.5 - 4 mm tons per panel
• Shearers cut at 35 - 65 t/min (2000-4000 tph)
• Output per year = 2 - 6 mm tons
• 6,000 - 20,000 t/day (max = 40,000)
• Cut 200-500 min/day
• – 20% - 45% of time (???)
• Capital intensive
• – $30M for face equipment only
• – $50-80M additional for mine / processing
• Require large, regularly shaped reserve
• – 50M ton minimum
• – Prefer 100-200M tons
• Mine-specific design / limited ability to move to other reserves

CONTINUOUS MINER SUMMARY

• Capital for section is $3-5 million
• Flexible, can move readily to other reserves
• One longwall usually requires three continuous miners for development
• Annual output for miner section is 0.3 - 0.8 million tpy

ENVIRONMENTAL

Longwall strata caves behind supports

– Surface subsides to maximum of 50-70% of seam thickness

– “Tilt” area may damage structures, so must provide special support methods at the structures to minimize damage

– Subsidence trails face position by a few days to a week or two, about 95% occurs in a few weeks

LONGWALL SUBSIDENCE

• Ground water flow is altered
• Some wells lose flow, temporarily or permanently; a few gain
• May need to drill wells deeper
• Connection from near surface to mine is possible if depth to aquifer is less than 40 x seam thickness (240 ft for 6-ft seam)

SUMMARY

Longwall (45% of UG output from only 60 faces -- average of 3 million tpy each)

– High output, high capital

– Low operating cost, 70-80% (?) reserve recovery

– Low flexibility

Continuous Miners

– Medium output, low-medium capital

– Moderate operating cost, 40-60% reserve recovery

– High flexibility

• Can use underground methods in +100 ft of overburden (actual minimum depth depends on whether strip ratio favors surface mining)
• – Roof subject to surface cracks when shallower
• Use longwall in large, thick (mine 6-ft min.), regularly-shaped reserves
• – Only economic method if seam is >1500 ft deep
• Else, use continuous miner and room & pillar
• While best walls far exceed cm productivity, on average, tons per manhour are close

Underground Mining Methods

Two Main Methods
- Room and Pillar

• Mostly with continuous miners

- Longwall – Develop longwall panels with room and pillar using continuous miners

- About 10% of underground production

• still comes from drilling and blasting

- Total underground output = 421mt (1997 data)

FIRST, MUST ACCESS THE MINE

- Drift (Adit)

• Seam outcrops, access from ground level

- Slope

• Drive incline in rock at up to 16 degrees
• Allows belt haulage

- Shaft

• Use: elevators/skips, for: people/coal
• Use shaft if >1500 feet, economics dictate

LIKE A CITY, OR LARGE BUILDING, SERVICES MUST BE PROVIDED

• Transport people (rail, rubber tired) - Transport supplies (materials / maintenance)
• Transport product (coal)
• Support roof
• Provide electrical power
• Provide fresh air (& suppress dust)
• Provide fresh water
• Get rid of waste water
• Dispose of trash

ROOM And PILLAR

• Mine “streets & avenues” (entries and crosscuts)
• Leave pillars to support roof (may mine later)

– Designed by formula

• Plan view-looks like city with “greenbelts”

– “Greenbelts” are large barrier pillars left to separate work areas

• Use continuous miner

MINE PLAN

• Main entries (7-9 openings)
• Submains (5-7 openings)
• Panels (panel entries, butt entries)
• Rooms (at times)
• Openings limited to 20-ft width

– Openings serve as air ducts and travelways – Return air is isolated from fresh air, two escapeways must be provided from face

• Longwall panels are solid coal blocks, usually 1000 ft by 10,000 ft, accessed by “gate” roads

ALL SERVICES EXIST TO SUPPORT MINING AT FACE
Continuous miner

- rips coal, using tungsten carbide bits

- miner mines at 4-25 t/m and conveys coal into shuttle cars

• Shuttle cars are electric (cable) “trucks” which haul for up to 600 feet or so (usual = 300-400 feet)

– Haul to feeder-breaker which acts as surge bin/crusher and feed coal onto belt

– Hold 3-25 tons/load, depending on seam thicknesss and amount of rock mined

FEEDER-BREAKER FEEDS COAL ONTO BELT CONVEYORS

• Conveyors transport coal to surface or into skips for shaft access

– Usual sizes - 42” to 72”

– Speeds - 500 - 800 fpm

• Longwall requires largest conveyors

– 54”-60” usual from face

ROOF BOLTS INSTALLED BY ROOF BOLTING MACHINE

• Roof supported by inserting reinforcing rods
• No one may work under unsupported roof – Cut depths limited to position of shuttle car operator (35’ to 40’ with remote control miner)
• When miner place changes, bolter moves in

– Bolt 3-6 min/row or 0.75-1.50 min/ft

– Use two bolter operators, twin-boom bolter

• A few operations attach bolters to miners, bolt as they advance

ROOF SUPPORT

• Insert bolts into the roof on regular pattern (3’-8’ length, usually)

– 4’ x 4’ or 5’ x 5’ most common

• Either “glue” (resin) a re-bar bolt in, or
• Use expansion bolt anchors or � Glue in the anchor only

– Anchors allow pre-tensioning of bolts

ROOF BOLTS GENERALLY WORK WELL

• Form “reinforced” rock, strong beam
• Or, may “hang” weak rock from stronger overlying rock layer
• Roof fall fatalities are now at 8 -12 per year

– Half are in violation of the law, under non-bolted roof

– Roof fall fatalities exceeded 100 per year around 1970

VENTILATION

• Provides oxygen, dilutes methane & dust

– Methane explosive when at 5-15% concentration Most coninuous miners have dust scrubber

– Draw air into ducts at front of miner

– Efficiency up to 96-97%

• Air directed to working face with brattice cloth (plastic curtains)
• Alternatively, hang tubing & use fan to draw air to face
• Fresh air ventilates one face only, then it is “return” air

– Separate air streams with concrete block walls or “stoppings”

• Maximum allowable methane content is 1%
• Control major flow with adjustable doors in airways (“regulators”)
• 150 - 400 ft/shift usual, tonnage depends on seam thickness

– 500 - 2000 tons/shift (usual)

• New miners load at 10 - 25 tpm
• Most continuous miners load only 60-120 min/shift

– Load only 12

– 10-25% of shift time

LONGWALL

• More nearly continuous method
• Analogous to “deli meat slicer” (shearer)
• Shearer mounted on chain conveyor
• – Coal cut falls onto conveyor
• Width of face usually 850 - 1100 ft
• – Depth of slice is 30 - 42 inches
• Behind face supported for 20’ or so by steel supports
• - each 1.50 or 1.75 m wide
• – Each support holds up to 600-1200 tons
• Supports connected to conveyor – By pushing, lowering & pulling
• - can walk conveyor and selves forward
• Panels (solid block of coal)
• – Usually 850’ - 1100’ wide & 7500’ - 15,000’ long
• – Contain 1.5 - 4 mm tons per panel
• Shearers cut at 35 - 65 t/min (2000-4000 tph)
• Output per year = 2 - 6 mm tons
• 6,000 - 20,000 t/day (max = 40,000)
• Cut 200-500 min/day
• – 20% - 45% of time (???)
• Capital intensive
• – $30M for face equipment only
• – $50-80M additional for mine / processing
• Require large, regularly shaped reserve
• – 50M ton minimum
• – Prefer 100-200M tons
• Mine-specific design / limited ability to move to other reserves

CONTINUOUS MINER SUMMARY

• Capital for section is $3-5 million
• Flexible, can move readily to other reserves
• One longwall usually requires three continuous miners for development
• Annual output for miner section is 0.3 - 0.8 million tpy

ENVIRONMENTAL

Longwall strata caves behind supports

– Surface subsides to maximum of 50-70% of seam thickness

– “Tilt” area may damage structures, so must provide special support methods at the structures to minimize damage

– Subsidence trails face position by a few days to a week or two, about 95% occurs in a few weeks

LONGWALL SUBSIDENCE

• Ground water flow is altered
• Some wells lose flow, temporarily or permanently; a few gain
• May need to drill wells deeper
• Connection from near surface to mine is possible if depth to aquifer is less than 40 x seam thickness (240 ft for 6-ft seam)

SUMMARY

Longwall (45% of UG output from only 60 faces -- average of 3 million tpy each)

– High output, high capital

– Low operating cost, 70-80% (?) reserve recovery

– Low flexibility

Continuous Miners

– Medium output, low-medium capital

– Moderate operating cost, 40-60% reserve recovery

– High flexibility

• Can use underground methods in +100 ft of overburden (actual minimum depth depends on whether strip ratio favors surface mining)
• – Roof subject to surface cracks when shallower
• Use longwall in large, thick (mine 6-ft min.), regularly-shaped reserves
• – Only economic method if seam is >1500 ft deep
• Else, use continuous miner and room & pillar
• While best walls far exceed cm productivity, on average, tons per manhour are close

Underground Mining Methods

Two Main Methods
- Room and Pillar

• Mostly with continuous miners

- Longwall – Develop longwall panels with room and pillar using continuous miners

- About 10% of underground production

• still comes from drilling and blasting

- Total underground output = 421mt (1997 data)

FIRST, MUST ACCESS THE MINE

- Drift (Adit)

• Seam outcrops, access from ground level

- Slope

• Drive incline in rock at up to 16 degrees
• Allows belt haulage

- Shaft

• Use: elevators/skips, for: people/coal
• Use shaft if >1500 feet, economics dictate

LIKE A CITY, OR LARGE BUILDING, SERVICES MUST BE PROVIDED

• Transport people (rail, rubber tired) - Transport supplies (materials / maintenance)
• Transport product (coal)
• Support roof
• Provide electrical power
• Provide fresh air (& suppress dust)
• Provide fresh water
• Get rid of waste water
• Dispose of trash

ROOM And PILLAR

• Mine “streets & avenues” (entries and crosscuts)
• Leave pillars to support roof (may mine later)

– Designed by formula

• Plan view-looks like city with “greenbelts”

– “Greenbelts” are large barrier pillars left to separate work areas

• Use continuous miner

MINE PLAN

• Main entries (7-9 openings)
• Submains (5-7 openings)
• Panels (panel entries, butt entries)
• Rooms (at times)
• Openings limited to 20-ft width

– Openings serve as air ducts and travelways – Return air is isolated from fresh air, two escapeways must be provided from face

• Longwall panels are solid coal blocks, usually 1000 ft by 10,000 ft, accessed by “gate” roads

ALL SERVICES EXIST TO SUPPORT MINING AT FACE
Continuous miner

- rips coal, using tungsten carbide bits

- miner mines at 4-25 t/m and conveys coal into shuttle cars

• Shuttle cars are electric (cable) “trucks” which haul for up to 600 feet or so (usual = 300-400 feet)

– Haul to feeder-breaker which acts as surge bin/crusher and feed coal onto belt

– Hold 3-25 tons/load, depending on seam thicknesss and amount of rock mined

FEEDER-BREAKER FEEDS COAL ONTO BELT CONVEYORS

• Conveyors transport coal to surface or into skips for shaft access

– Usual sizes - 42” to 72”

– Speeds - 500 - 800 fpm

• Longwall requires largest conveyors

– 54”-60” usual from face

ROOF BOLTS INSTALLED BY ROOF BOLTING MACHINE

• Roof supported by inserting reinforcing rods
• No one may work under unsupported roof – Cut depths limited to position of shuttle car operator (35’ to 40’ with remote control miner)
• When miner place changes, bolter moves in

– Bolt 3-6 min/row or 0.75-1.50 min/ft

– Use two bolter operators, twin-boom bolter

• A few operations attach bolters to miners, bolt as they advance

ROOF SUPPORT

• Insert bolts into the roof on regular pattern (3’-8’ length, usually)

– 4’ x 4’ or 5’ x 5’ most common

• Either “glue” (resin) a re-bar bolt in, or
• Use expansion bolt anchors or � Glue in the anchor only

– Anchors allow pre-tensioning of bolts

ROOF BOLTS GENERALLY WORK WELL

• Form “reinforced” rock, strong beam
• Or, may “hang” weak rock from stronger overlying rock layer
• Roof fall fatalities are now at 8 -12 per year

– Half are in violation of the law, under non-bolted roof

– Roof fall fatalities exceeded 100 per year around 1970

VENTILATION

• Provides oxygen, dilutes methane & dust

– Methane explosive when at 5-15% concentration Most coninuous miners have dust scrubber

– Draw air into ducts at front of miner

– Efficiency up to 96-97%

• Air directed to working face with brattice cloth (plastic curtains)
• Alternatively, hang tubing & use fan to draw air to face
• Fresh air ventilates one face only, then it is “return” air

– Separate air streams with concrete block walls or “stoppings”

• Maximum allowable methane content is 1%
• Control major flow with adjustable doors in airways (“regulators”)
• 150 - 400 ft/shift usual, tonnage depends on seam thickness

– 500 - 2000 tons/shift (usual)

• New miners load at 10 - 25 tpm
• Most continuous miners load only 60-120 min/shift

– Load only 12

– 10-25% of shift time

LONGWALL

• More nearly continuous method
• Analogous to “deli meat slicer” (shearer)
• Shearer mounted on chain conveyor
• – Coal cut falls onto conveyor
• Width of face usually 850 - 1100 ft
• – Depth of slice is 30 - 42 inches
• Behind face supported for 20’ or so by steel supports
• - each 1.50 or 1.75 m wide
• – Each support holds up to 600-1200 tons
• Supports connected to conveyor – By pushing, lowering & pulling
• - can walk conveyor and selves forward
• Panels (solid block of coal)
• – Usually 850’ - 1100’ wide & 7500’ - 15,000’ long
• – Contain 1.5 - 4 mm tons per panel
• Shearers cut at 35 - 65 t/min (2000-4000 tph)
• Output per year = 2 - 6 mm tons
• 6,000 - 20,000 t/day (max = 40,000)
• Cut 200-500 min/day
• – 20% - 45% of time (???)
• Capital intensive
• – $30M for face equipment only
• – $50-80M additional for mine / processing
• Require large, regularly shaped reserve
• – 50M ton minimum
• – Prefer 100-200M tons
• Mine-specific design / limited ability to move to other reserves

CONTINUOUS MINER SUMMARY

• Capital for section is $3-5 million
• Flexible, can move readily to other reserves
• One longwall usually requires three continuous miners for development
• Annual output for miner section is 0.3 - 0.8 million tpy

ENVIRONMENTAL

Longwall strata caves behind supports

– Surface subsides to maximum of 50-70% of seam thickness

– “Tilt” area may damage structures, so must provide special support methods at the structures to minimize damage

– Subsidence trails face position by a few days to a week or two, about 95% occurs in a few weeks

LONGWALL SUBSIDENCE

• Ground water flow is altered
• Some wells lose flow, temporarily or permanently; a few gain
• May need to drill wells deeper
• Connection from near surface to mine is possible if depth to aquifer is less than 40 x seam thickness (240 ft for 6-ft seam)

SUMMARY

Longwall (45% of UG output from only 60 faces -- average of 3 million tpy each)

– High output, high capital

– Low operating cost, 70-80% (?) reserve recovery

– Low flexibility

Continuous Miners

– Medium output, low-medium capital

– Moderate operating cost, 40-60% reserve recovery

– High flexibility

• Can use underground methods in +100 ft of overburden (actual minimum depth depends on whether strip ratio favors surface mining)
• – Roof subject to surface cracks when shallower
• Use longwall in large, thick (mine 6-ft min.), regularly-shaped reserves
• – Only economic method if seam is >1500 ft deep
• Else, use continuous miner and room & pillar
• While best walls far exceed cm productivity, on average, tons per manhour are close

Underground Mining Methods

Two Main Methods
- Room and Pillar

• Mostly with continuous miners

- Longwall – Develop longwall panels with room and pillar using continuous miners

- About 10% of underground production

• still comes from drilling and blasting

- Total underground output = 421mt (1997 data)

FIRST, MUST ACCESS THE MINE

- Drift (Adit)

• Seam outcrops, access from ground level

- Slope

• Drive incline in rock at up to 16 degrees
• Allows belt haulage

- Shaft

• Use: elevators/skips, for: people/coal
• Use shaft if >1500 feet, economics dictate

LIKE A CITY, OR LARGE BUILDING, SERVICES MUST BE PROVIDED

• Transport people (rail, rubber tired) - Transport supplies (materials / maintenance)
• Transport product (coal)
• Support roof
• Provide electrical power
• Provide fresh air (& suppress dust)
• Provide fresh water
• Get rid of waste water
• Dispose of trash

ROOM And PILLAR

• Mine “streets & avenues” (entries and crosscuts)
• Leave pillars to support roof (may mine later)

– Designed by formula

• Plan view-looks like city with “greenbelts”

– “Greenbelts” are large barrier pillars left to separate work areas

• Use continuous miner

MINE PLAN

• Main entries (7-9 openings)
• Submains (5-7 openings)
• Panels (panel entries, butt entries)
• Rooms (at times)
• Openings limited to 20-ft width

– Openings serve as air ducts and travelways – Return air is isolated from fresh air, two escapeways must be provided from face

• Longwall panels are solid coal blocks, usually 1000 ft by 10,000 ft, accessed by “gate” roads

ALL SERVICES EXIST TO SUPPORT MINING AT FACE
Continuous miner

- rips coal, using tungsten carbide bits

- miner mines at 4-25 t/m and conveys coal into shuttle cars

• Shuttle cars are electric (cable) “trucks” which haul for up to 600 feet or so (usual = 300-400 feet)

– Haul to feeder-breaker which acts as surge bin/crusher and feed coal onto belt

– Hold 3-25 tons/load, depending on seam thicknesss and amount of rock mined

FEEDER-BREAKER FEEDS COAL ONTO BELT CONVEYORS

• Conveyors transport coal to surface or into skips for shaft access

– Usual sizes - 42” to 72”

– Speeds - 500 - 800 fpm

• Longwall requires largest conveyors

– 54”-60” usual from face

ROOF BOLTS INSTALLED BY ROOF BOLTING MACHINE

• Roof supported by inserting reinforcing rods
• No one may work under unsupported roof – Cut depths limited to position of shuttle car operator (35’ to 40’ with remote control miner)
• When miner place changes, bolter moves in

– Bolt 3-6 min/row or 0.75-1.50 min/ft

– Use two bolter operators, twin-boom bolter

• A few operations attach bolters to miners, bolt as they advance

ROOF SUPPORT

• Insert bolts into the roof on regular pattern (3’-8’ length, usually)

– 4’ x 4’ or 5’ x 5’ most common

• Either “glue” (resin) a re-bar bolt in, or
• Use expansion bolt anchors or � Glue in the anchor only

– Anchors allow pre-tensioning of bolts

ROOF BOLTS GENERALLY WORK WELL

• Form “reinforced” rock, strong beam
• Or, may “hang” weak rock from stronger overlying rock layer
• Roof fall fatalities are now at 8 -12 per year

– Half are in violation of the law, under non-bolted roof

– Roof fall fatalities exceeded 100 per year around 1970

VENTILATION

• Provides oxygen, dilutes methane & dust

– Methane explosive when at 5-15% concentration Most coninuous miners have dust scrubber

– Draw air into ducts at front of miner

– Efficiency up to 96-97%

• Air directed to working face with brattice cloth (plastic curtains)
• Alternatively, hang tubing & use fan to draw air to face
• Fresh air ventilates one face only, then it is “return” air

– Separate air streams with concrete block walls or “stoppings”

• Maximum allowable methane content is 1%
• Control major flow with adjustable doors in airways (“regulators”)
• 150 - 400 ft/shift usual, tonnage depends on seam thickness

– 500 - 2000 tons/shift (usual)

• New miners load at 10 - 25 tpm
• Most continuous miners load only 60-120 min/shift

– Load only 12

– 10-25% of shift time

LONGWALL

• More nearly continuous method
• Analogous to “deli meat slicer” (shearer)
• Shearer mounted on chain conveyor
• – Coal cut falls onto conveyor
• Width of face usually 850 - 1100 ft
• – Depth of slice is 30 - 42 inches
• Behind face supported for 20’ or so by steel supports
• - each 1.50 or 1.75 m wide
• – Each support holds up to 600-1200 tons
• Supports connected to conveyor – By pushing, lowering & pulling
• - can walk conveyor and selves forward
• Panels (solid block of coal)
• – Usually 850’ - 1100’ wide & 7500’ - 15,000’ long
• – Contain 1.5 - 4 mm tons per panel
• Shearers cut at 35 - 65 t/min (2000-4000 tph)
• Output per year = 2 - 6 mm tons
• 6,000 - 20,000 t/day (max = 40,000)
• Cut 200-500 min/day
• – 20% - 45% of time (???)
• Capital intensive
• – $30M for face equipment only
• – $50-80M additional for mine / processing
• Require large, regularly shaped reserve
• – 50M ton minimum
• – Prefer 100-200M tons
• Mine-specific design / limited ability to move to other reserves

CONTINUOUS MINER SUMMARY

• Capital for section is $3-5 million
• Flexible, can move readily to other reserves
• One longwall usually requires three continuous miners for development
• Annual output for miner section is 0.3 - 0.8 million tpy

ENVIRONMENTAL

Longwall strata caves behind supports

– Surface subsides to maximum of 50-70% of seam thickness

– “Tilt” area may damage structures, so must provide special support methods at the structures to minimize damage

– Subsidence trails face position by a few days to a week or two, about 95% occurs in a few weeks

LONGWALL SUBSIDENCE

• Ground water flow is altered
• Some wells lose flow, temporarily or permanently; a few gain
• May need to drill wells deeper
• Connection from near surface to mine is possible if depth to aquifer is less than 40 x seam thickness (240 ft for 6-ft seam)

SUMMARY

Longwall (45% of UG output from only 60 faces -- average of 3 million tpy each)

– High output, high capital

– Low operating cost, 70-80% (?) reserve recovery

– Low flexibility

Continuous Miners

– Medium output, low-medium capital

– Moderate operating cost, 40-60% reserve recovery

– High flexibility

• Can use underground methods in +100 ft of overburden (actual minimum depth depends on whether strip ratio favors surface mining)
• – Roof subject to surface cracks when shallower
• Use longwall in large, thick (mine 6-ft min.), regularly-shaped reserves
• – Only economic method if seam is >1500 ft deep
• Else, use continuous miner and room & pillar
• While best walls far exceed cm productivity, on average, tons per manhour are close

Gold Mining with Cyanide

Repeal of the Ban on Cyanide Heap Leaching in Gold Mining
 

WHAT IS CYANIDE AND WHAT DOES IT DO IN THE ENVIRONMENT
Cyanide is a general term, referring to various specific cyanide compounds. Cyanide (CN) itself is a simple, organic anion (negatively charged ion) consisting of carbon and nitrogen. Despite often-heard references to “pure cyanide,” it actually exists only as an anion, so is only a component of other compounds.

Even though cyanide is a poison, trace amounts of cyanide compounds occur naturally in our bodies and in many foods. Even over a lifetime of exposure, trace amounts pose no threat to human health. Cyanide does not build up in the body. The liver removes it. As one might expect, cyanide compounds are used in certain herbicides. But some common drugs—including the pain reliever ibuprofen and the anti-inflammatory agent naproxen—also contain cyanide compounds, or are derived directly from them.

Today, U.S. chemical manufacturing industries consume more than 10 times the amount of cyanide compounds than are used in domestic gold mining to manufacture products like nylon and other polyamides, acrylics and certain plastics. Cyanide compounds are also used to harden steel and to electroplate copper and precious metals.

Cyanide heap leach solutions are very alkaline because at a ph of 8 or below CN vaporizes into the air. In the air, the poison is quickly dispersed and would only be dangerous in a very small area close to the vaporizing solution. Therefore if these solutions do escape into surface water, they will be diluted by the lower ph surface water and soon dissipate into the air, becoming harmless.

Other natural elements including sunlight also degrade cyanide into harmless compounds:
“Various species of bacteria, fungi, algae, yeasts and plants, along with their associated enzymes and amino acids, are known to oxidize cyanide naturally.”

HOW DOES CYANIDE LEACHING WORK
A weak solution containing a quantity of sodium cyanide (0.015 percent average) is percolated over crushed ore to dissolve the gold. The leach solutions are carefully buffered with an alkali (usually lime) to prevent the possible generation of hazardous hydrogen cyanide gas. The gold bearing solution is collected and the gold removed. The leaching solution is then reused. The whole process takes place on top of an impermeable, double or triple layered liner to collect all of the valuable gold and prevent the escape of dangerous CN.

POLITICAL HISTORY OF CYANIDE LEACHING
In 1996, environmental groups headed by MEIC from Missoula launched an attack on mining through the initiative process. Miners defended their industry and I-122 was defeated. A great deal of out of state money was spent on this campaign by both sides. There was another ballot issue that year: I-125, sponsored by MontPIRG which is a Nader group that percolated up from the Univerity of Montana campus at Missoula. I-125 prevented businesses spending ANY money to defend themselves against ballot issues. In the heated battle over I-122, this seemingly innocuous ballot issue was overlooked by business and the public. I-125 did not put any limitations on spending by non-profit groups on Montana ballot issues. I-125 passed in 1996.

After the passage of the business spending ban, I-125, MEIC decided that they had a good chance to pass an anti-mining bill in the next election because the miners could not fight back. They said as much on their website. This time they sensationalized the issue by concentrating on cyanide. Just two weeks before the election the Montana Supreme Court ruled that the ban on business spending in ballot issue elections was unconstitutional but it was too late for the miners to mount an effective defense. I-137 passed in 1998. No other state in America bans the use of cyanide in mining.

BENEFITS
Mining in Montana has rapidly declined in recent years due to the regulatory climate in the state. Since cyanide leaching is the only economic means of recovering many of Montana’s most important gold and silver deposits, repealing the cyanide ban will go a long way towards improving that climate thus helping to diversify our economy. Canyon Resources lists the economic losses to Montana from the passage of the cyanide ban just related for their projects alone.

“The imposition of I-137, with its total ban on the use of the only economically viable technology to recover gold and silver from the McDonald and Seven-Up Pete deposits, has deprived the citizens of Montana, local communities and their workers, and the State of Montana of the following otherwise available assets:
a. Royalty payments of more than $89 million ($6,357,142 annually for 14 years) to the State School Trust System, primarily designated for Montana Tech
b. Long-term jobs at wages approximately twice the current average income in Montana
c. Severance and local taxes of at least $56 million
d. More than $1 billion (average of $75 million/year) in purchases of goods and services during operations
e. More than $40 million in site construction work at startup”

With the lifting of the ban Canyon and other companies would resume exploration in Montana and new projects as well as old ones that have been put on hold will strengthen our economy with royalties, taxes, jobs and sales for related businesses. The $ 89 million royalty from the Seven Up Pete project alone spread over 14 years will amount to 10% of the total current yearly income for Montana schools from state trust lands

DRAWBACKS
There are no drawbacks - only risks that can be managed. Like bleach and gasoline, Cyanide (CN) is a deadly poison when a toxic amount is present in the blood of mammals and fish. Therefore extra care must be taken in the handling and containment of cyanide solutions. I-147 mandates a high level of environmental protection.

Since cyanide degrades into non-toxic substances fairly easily and is quickly dispersed and diluted in the natural environment the damage from escaped cyanide though it can be significant is thankfully short term. Humans who ingest a non-fatal dose of cyanide quickly recover and there is no evidence of long-term consequences or buildup of cyanide in the body. There has never been a human fatality in Montana caused by cyanide used in mining.

There have been fish kills due to accidental releases of cyanide from mining. Most of these incidents have been minor and none of them have long lasting effects. Our research found no major fish kills in Montana. The fish stocks are repopulated from unaffected downstream fisheries. The mining industry and the agencies that regulate them have learned from these incidents and are better equipped to prevent them.

Gold Mining with Cyanide

Repeal of the Ban on Cyanide Heap Leaching in Gold Mining
 

WHAT IS CYANIDE AND WHAT DOES IT DO IN THE ENVIRONMENT
Cyanide is a general term, referring to various specific cyanide compounds. Cyanide (CN) itself is a simple, organic anion (negatively charged ion) consisting of carbon and nitrogen. Despite often-heard references to “pure cyanide,” it actually exists only as an anion, so is only a component of other compounds.

Even though cyanide is a poison, trace amounts of cyanide compounds occur naturally in our bodies and in many foods. Even over a lifetime of exposure, trace amounts pose no threat to human health. Cyanide does not build up in the body. The liver removes it. As one might expect, cyanide compounds are used in certain herbicides. But some common drugs—including the pain reliever ibuprofen and the anti-inflammatory agent naproxen—also contain cyanide compounds, or are derived directly from them.

Today, U.S. chemical manufacturing industries consume more than 10 times the amount of cyanide compounds than are used in domestic gold mining to manufacture products like nylon and other polyamides, acrylics and certain plastics. Cyanide compounds are also used to harden steel and to electroplate copper and precious metals.

Cyanide heap leach solutions are very alkaline because at a ph of 8 or below CN vaporizes into the air. In the air, the poison is quickly dispersed and would only be dangerous in a very small area close to the vaporizing solution. Therefore if these solutions do escape into surface water, they will be diluted by the lower ph surface water and soon dissipate into the air, becoming harmless.

Other natural elements including sunlight also degrade cyanide into harmless compounds:
“Various species of bacteria, fungi, algae, yeasts and plants, along with their associated enzymes and amino acids, are known to oxidize cyanide naturally.”

HOW DOES CYANIDE LEACHING WORK
A weak solution containing a quantity of sodium cyanide (0.015 percent average) is percolated over crushed ore to dissolve the gold. The leach solutions are carefully buffered with an alkali (usually lime) to prevent the possible generation of hazardous hydrogen cyanide gas. The gold bearing solution is collected and the gold removed. The leaching solution is then reused. The whole process takes place on top of an impermeable, double or triple layered liner to collect all of the valuable gold and prevent the escape of dangerous CN.

POLITICAL HISTORY OF CYANIDE LEACHING
In 1996, environmental groups headed by MEIC from Missoula launched an attack on mining through the initiative process. Miners defended their industry and I-122 was defeated. A great deal of out of state money was spent on this campaign by both sides. There was another ballot issue that year: I-125, sponsored by MontPIRG which is a Nader group that percolated up from the Univerity of Montana campus at Missoula. I-125 prevented businesses spending ANY money to defend themselves against ballot issues. In the heated battle over I-122, this seemingly innocuous ballot issue was overlooked by business and the public. I-125 did not put any limitations on spending by non-profit groups on Montana ballot issues. I-125 passed in 1996.

After the passage of the business spending ban, I-125, MEIC decided that they had a good chance to pass an anti-mining bill in the next election because the miners could not fight back. They said as much on their website. This time they sensationalized the issue by concentrating on cyanide. Just two weeks before the election the Montana Supreme Court ruled that the ban on business spending in ballot issue elections was unconstitutional but it was too late for the miners to mount an effective defense. I-137 passed in 1998. No other state in America bans the use of cyanide in mining.

BENEFITS
Mining in Montana has rapidly declined in recent years due to the regulatory climate in the state. Since cyanide leaching is the only economic means of recovering many of Montana’s most important gold and silver deposits, repealing the cyanide ban will go a long way towards improving that climate thus helping to diversify our economy. Canyon Resources lists the economic losses to Montana from the passage of the cyanide ban just related for their projects alone.

“The imposition of I-137, with its total ban on the use of the only economically viable technology to recover gold and silver from the McDonald and Seven-Up Pete deposits, has deprived the citizens of Montana, local communities and their workers, and the State of Montana of the following otherwise available assets:
a. Royalty payments of more than $89 million ($6,357,142 annually for 14 years) to the State School Trust System, primarily designated for Montana Tech
b. Long-term jobs at wages approximately twice the current average income in Montana
c. Severance and local taxes of at least $56 million
d. More than $1 billion (average of $75 million/year) in purchases of goods and services during operations
e. More than $40 million in site construction work at startup”

With the lifting of the ban Canyon and other companies would resume exploration in Montana and new projects as well as old ones that have been put on hold will strengthen our economy with royalties, taxes, jobs and sales for related businesses. The $ 89 million royalty from the Seven Up Pete project alone spread over 14 years will amount to 10% of the total current yearly income for Montana schools from state trust lands

DRAWBACKS
There are no drawbacks - only risks that can be managed. Like bleach and gasoline, Cyanide (CN) is a deadly poison when a toxic amount is present in the blood of mammals and fish. Therefore extra care must be taken in the handling and containment of cyanide solutions. I-147 mandates a high level of environmental protection.

Since cyanide degrades into non-toxic substances fairly easily and is quickly dispersed and diluted in the natural environment the damage from escaped cyanide though it can be significant is thankfully short term. Humans who ingest a non-fatal dose of cyanide quickly recover and there is no evidence of long-term consequences or buildup of cyanide in the body. There has never been a human fatality in Montana caused by cyanide used in mining.

There have been fish kills due to accidental releases of cyanide from mining. Most of these incidents have been minor and none of them have long lasting effects. Our research found no major fish kills in Montana. The fish stocks are repopulated from unaffected downstream fisheries. The mining industry and the agencies that regulate them have learned from these incidents and are better equipped to prevent them.

Gold Mining with Cyanide

Repeal of the Ban on Cyanide Heap Leaching in Gold Mining
 

WHAT IS CYANIDE AND WHAT DOES IT DO IN THE ENVIRONMENT
Cyanide is a general term, referring to various specific cyanide compounds. Cyanide (CN) itself is a simple, organic anion (negatively charged ion) consisting of carbon and nitrogen. Despite often-heard references to “pure cyanide,” it actually exists only as an anion, so is only a component of other compounds.

Even though cyanide is a poison, trace amounts of cyanide compounds occur naturally in our bodies and in many foods. Even over a lifetime of exposure, trace amounts pose no threat to human health. Cyanide does not build up in the body. The liver removes it. As one might expect, cyanide compounds are used in certain herbicides. But some common drugs—including the pain reliever ibuprofen and the anti-inflammatory agent naproxen—also contain cyanide compounds, or are derived directly from them.

Today, U.S. chemical manufacturing industries consume more than 10 times the amount of cyanide compounds than are used in domestic gold mining to manufacture products like nylon and other polyamides, acrylics and certain plastics. Cyanide compounds are also used to harden steel and to electroplate copper and precious metals.

Cyanide heap leach solutions are very alkaline because at a ph of 8 or below CN vaporizes into the air. In the air, the poison is quickly dispersed and would only be dangerous in a very small area close to the vaporizing solution. Therefore if these solutions do escape into surface water, they will be diluted by the lower ph surface water and soon dissipate into the air, becoming harmless.

Other natural elements including sunlight also degrade cyanide into harmless compounds:
“Various species of bacteria, fungi, algae, yeasts and plants, along with their associated enzymes and amino acids, are known to oxidize cyanide naturally.”

HOW DOES CYANIDE LEACHING WORK
A weak solution containing a quantity of sodium cyanide (0.015 percent average) is percolated over crushed ore to dissolve the gold. The leach solutions are carefully buffered with an alkali (usually lime) to prevent the possible generation of hazardous hydrogen cyanide gas. The gold bearing solution is collected and the gold removed. The leaching solution is then reused. The whole process takes place on top of an impermeable, double or triple layered liner to collect all of the valuable gold and prevent the escape of dangerous CN.

POLITICAL HISTORY OF CYANIDE LEACHING
In 1996, environmental groups headed by MEIC from Missoula launched an attack on mining through the initiative process. Miners defended their industry and I-122 was defeated. A great deal of out of state money was spent on this campaign by both sides. There was another ballot issue that year: I-125, sponsored by MontPIRG which is a Nader group that percolated up from the Univerity of Montana campus at Missoula. I-125 prevented businesses spending ANY money to defend themselves against ballot issues. In the heated battle over I-122, this seemingly innocuous ballot issue was overlooked by business and the public. I-125 did not put any limitations on spending by non-profit groups on Montana ballot issues. I-125 passed in 1996.

After the passage of the business spending ban, I-125, MEIC decided that they had a good chance to pass an anti-mining bill in the next election because the miners could not fight back. They said as much on their website. This time they sensationalized the issue by concentrating on cyanide. Just two weeks before the election the Montana Supreme Court ruled that the ban on business spending in ballot issue elections was unconstitutional but it was too late for the miners to mount an effective defense. I-137 passed in 1998. No other state in America bans the use of cyanide in mining.

BENEFITS
Mining in Montana has rapidly declined in recent years due to the regulatory climate in the state. Since cyanide leaching is the only economic means of recovering many of Montana’s most important gold and silver deposits, repealing the cyanide ban will go a long way towards improving that climate thus helping to diversify our economy. Canyon Resources lists the economic losses to Montana from the passage of the cyanide ban just related for their projects alone.

“The imposition of I-137, with its total ban on the use of the only economically viable technology to recover gold and silver from the McDonald and Seven-Up Pete deposits, has deprived the citizens of Montana, local communities and their workers, and the State of Montana of the following otherwise available assets:
a. Royalty payments of more than $89 million ($6,357,142 annually for 14 years) to the State School Trust System, primarily designated for Montana Tech
b. Long-term jobs at wages approximately twice the current average income in Montana
c. Severance and local taxes of at least $56 million
d. More than $1 billion (average of $75 million/year) in purchases of goods and services during operations
e. More than $40 million in site construction work at startup”

With the lifting of the ban Canyon and other companies would resume exploration in Montana and new projects as well as old ones that have been put on hold will strengthen our economy with royalties, taxes, jobs and sales for related businesses. The $ 89 million royalty from the Seven Up Pete project alone spread over 14 years will amount to 10% of the total current yearly income for Montana schools from state trust lands

DRAWBACKS
There are no drawbacks - only risks that can be managed. Like bleach and gasoline, Cyanide (CN) is a deadly poison when a toxic amount is present in the blood of mammals and fish. Therefore extra care must be taken in the handling and containment of cyanide solutions. I-147 mandates a high level of environmental protection.

Since cyanide degrades into non-toxic substances fairly easily and is quickly dispersed and diluted in the natural environment the damage from escaped cyanide though it can be significant is thankfully short term. Humans who ingest a non-fatal dose of cyanide quickly recover and there is no evidence of long-term consequences or buildup of cyanide in the body. There has never been a human fatality in Montana caused by cyanide used in mining.

There have been fish kills due to accidental releases of cyanide from mining. Most of these incidents have been minor and none of them have long lasting effects. Our research found no major fish kills in Montana. The fish stocks are repopulated from unaffected downstream fisheries. The mining industry and the agencies that regulate them have learned from these incidents and are better equipped to prevent them.