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Highwall mining

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Safdar Ali

This document discusses highwall mining systems and methods. It outlines key topics like highwall mining systems, geotechnical issues and stability rating, guidance control, failures and their causes. Highwall mining involves using remote controlled machinery to drive parallel roadways up to 500 meters into a highwall or coal seam. Proper geotechnical assessment and guidance control are important for ensuring stability and preventing failures of the unsupported roof, pillars and entire panels. The conclusions state that highwall mining provides high productivity but is best suited to certain conditions and depths less than 500 meters.

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Highwall mining
Highwall Mining
Presentation outline Highwall mining systems Geotechnical issues & rating Guidance Control Failures and causes Conclusions Highwall Mining
Highwall Mining Driving parallel roadways into highwall/ coal seam using remote controlled mining machinery 200 - 500 m depth Highwall Mining
Highwall Mining System (1) Addington Highwall Mining system Addcar system Highwall Mining
Highwall Mining Systems (1) cont. Addcar System Launch vehicle Conveyor cars Highwall Mining
Highwall Mining Systems (2) Archveyor system Highwall Mining
Highwall Mining Highwall Mining Systems (3) Auger system
Geotechnical Issues & Rating Unsupported span stability Pillar stability Panel Stability Case studies Design guidelines Highwall Mining
Highwall Mining Unsupported Span Stability Typical failure mechanism delamination & snap-through Simple analytical thickness of roof plate, Y, Probabilistic approach Realistic prediction Geology, rock properties
Highwall Mining Pillar Stability Lab testing of coal strength Empirical approach Pillar stability modelling Applications and verification in field P illa r S tre n g th v . W id th /H e ig h t 0 5 1 0 1 5 2 0 2 5 0 1 2 3 4 5 P il la r W id th /H e ig h t PillarPeakStress(Strength) P ro p o s e d H W M W a g n e r B ie n a w s k i A ve ra g e Tre n d lin e 0.36W/h)(0.64*6.00 Strength 0.36w/h)(0.64*6.00 Strength 0.44w/h]w[0.69W
Highwall Mining Panel Stability Panel stability depends on local mine stiffness Panel factor of safety One pillar failure may lead to total panel failure Roadways to be driven in perfect parallel
Design Guidelines 15 key factors are considered, e.g. roof condition; mine reserve etc.; Key factors are weighted differently in HMI; Uncertainty on judgement is incorporated. A given site has two index values: HMI rating, confidence level. Recommendation is given for any HMI/Confidence ratings. 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Highwall Mining Index (HMI) ConfidenceLevel(%) 1 Good site for CHM mining 2 Possibly a good site for CHM mining. More information is need. 3 Site apparently unsuitable for CHM mining. Further evaluation may be needed if new information is available 4 Site unsuitable for CHM mining. Transition zone Example pit 1 Highwall Mining Index (HMI) has been developed Highwall Mining
Guidance Control (1) Driving parallel roadways remote miner 200 to 500 m depth Problems Cut-throughs connection Pillar failure - frequent roof falls Limited penetration depth 7424250 7424300 7424350 7424400 7424450 7424500 7424550 7424600 7424650 7424700 7424750 707000 707100 707200 707300 707400 707500 panel 4 #41-67 panel 3 #21-40 panel 2 #11-20 panel 1 #1-10 Cracks on top of the highwall -Survey data Cracks on the face of the highwall - Observation North Highwall Mining
Guidance Control (2) Problems to solve Uncertainty in pillar size Frequent cut-throughs Reduced penetration depth pillar/panel failure Guidance system Military grade Inertial Navigation System Independent odometer Controlling computers Operator displace and interface Achievements Used in every HWM system in Australia No mining equipment lost due to collapse Penetration depths increased - 350m to 510m Highwall Mining
Failures (1) Panel failure Highwall Mining Before After
Local panel failure at Yarrabee MinePanel failure at Ulan Mine Highwall Mining Failures (2) Panel failure
Lack of site investigation Poor knowledge on span stability Inadequate pillar design Poor guidance control Critical panel width Lack of knowledge on insitu stresses No monitoring and feedback Factors contributing to pillar/panel failures Highwall Mining
Production Production ~ 1 million tonnes per year Employees 50 (High productivity main advantage) Continuous inert gas injection @ 150 l/s Penetration depth varies 100 to 500 m (Av 300m) Gas issues Stability issues Each roadway driven almost in one day (or less) Production share in Australia 1% Highwall Mining
Conclusions Main attraction high productivity and low cost Suitable for certain conditions 500 m boundary May lead to more fires and collapses Around 50% of extraction Creates problems for deeper reserves Production share in Australia 1% Punch longwall preferred for large reserves High production and longer term view Highwall Mining

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Highwall mining

  • 3. Presentation outline Highwall mining systems Geotechnical issues & rating Guidance Control Failures and causes Conclusions Highwall Mining
  • 4. Highwall Mining Driving parallel roadways into highwall/ coal seam using remote controlled mining machinery 200 - 500 m depth Highwall Mining
  • 5. Highwall Mining System (1) Addington Highwall Mining system Addcar system Highwall Mining
  • 6. Highwall Mining Systems (1) cont. Addcar System Launch vehicle Conveyor cars Highwall Mining
  • 7. Highwall Mining Systems (2) Archveyor system Highwall Mining
  • 8. Highwall Mining Highwall Mining Systems (3) Auger system
  • 9. Geotechnical Issues & Rating Unsupported span stability Pillar stability Panel Stability Case studies Design guidelines Highwall Mining
  • 10. Highwall Mining Unsupported Span Stability Typical failure mechanism delamination & snap-through Simple analytical thickness of roof plate, Y, Probabilistic approach Realistic prediction Geology, rock properties
  • 11. Highwall Mining Pillar Stability Lab testing of coal strength Empirical approach Pillar stability modelling Applications and verification in field P illa r S tre n g th v . W id th /H e ig h t 0 5 1 0 1 5 2 0 2 5 0 1 2 3 4 5 P il la r W id th /H e ig h t PillarPeakStress(Strength) P ro p o s e d H W M W a g n e r B ie n a w s k i A ve ra g e Tre n d lin e 0.36W/h)(0.64*6.00 Strength 0.36w/h)(0.64*6.00 Strength 0.44w/h]w[0.69W
  • 12. Highwall Mining Panel Stability Panel stability depends on local mine stiffness Panel factor of safety One pillar failure may lead to total panel failure Roadways to be driven in perfect parallel
  • 13. Design Guidelines 15 key factors are considered, e.g. roof condition; mine reserve etc.; Key factors are weighted differently in HMI; Uncertainty on judgement is incorporated. A given site has two index values: HMI rating, confidence level. Recommendation is given for any HMI/Confidence ratings. 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Highwall Mining Index (HMI) ConfidenceLevel(%) 1 Good site for CHM mining 2 Possibly a good site for CHM mining. More information is need. 3 Site apparently unsuitable for CHM mining. Further evaluation may be needed if new information is available 4 Site unsuitable for CHM mining. Transition zone Example pit 1 Highwall Mining Index (HMI) has been developed Highwall Mining
  • 14. Guidance Control (1) Driving parallel roadways remote miner 200 to 500 m depth Problems Cut-throughs connection Pillar failure - frequent roof falls Limited penetration depth 7424250 7424300 7424350 7424400 7424450 7424500 7424550 7424600 7424650 7424700 7424750 707000 707100 707200 707300 707400 707500 panel 4 #41-67 panel 3 #21-40 panel 2 #11-20 panel 1 #1-10 Cracks on top of the highwall -Survey data Cracks on the face of the highwall - Observation North Highwall Mining
  • 15. Guidance Control (2) Problems to solve Uncertainty in pillar size Frequent cut-throughs Reduced penetration depth pillar/panel failure Guidance system Military grade Inertial Navigation System Independent odometer Controlling computers Operator displace and interface Achievements Used in every HWM system in Australia No mining equipment lost due to collapse Penetration depths increased - 350m to 510m Highwall Mining
  • 16. Failures (1) Panel failure Highwall Mining Before After
  • 17. Local panel failure at Yarrabee MinePanel failure at Ulan Mine Highwall Mining Failures (2) Panel failure
  • 18. Lack of site investigation Poor knowledge on span stability Inadequate pillar design Poor guidance control Critical panel width Lack of knowledge on insitu stresses No monitoring and feedback Factors contributing to pillar/panel failures Highwall Mining
  • 19. Production Production ~ 1 million tonnes per year Employees 50 (High productivity main advantage) Continuous inert gas injection @ 150 l/s Penetration depth varies 100 to 500 m (Av 300m) Gas issues Stability issues Each roadway driven almost in one day (or less) Production share in Australia 1% Highwall Mining
  • 20. Conclusions Main attraction high productivity and low cost Suitable for certain conditions 500 m boundary May lead to more fires and collapses Around 50% of extraction Creates problems for deeper reserves Production share in Australia 1% Punch longwall preferred for large reserves High production and longer term view Highwall Mining