Recent Secondary Extraction Experience at Cook Colliery in a Multiseam Environment
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Recent Secondary Extraction Experience at Cook Colliery in a Multiseam Environment William Lawrence Geowork Engineering 1
description
Recent Secondary Extraction Experience at Cook Colliery in a Multiseam Environment . William Lawrence Geowork Engineering. Castor Seam Workings. Argo Seam Workings (Castor superimposed). N. Argo Seam Major Structure. Lithology. CMRR – South Argo. CMRR – North Argo. - PowerPoint PPT Presentation
Transcript of Recent Secondary Extraction Experience at Cook Colliery in a Multiseam Environment
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Recent Secondary Extraction Experience at Cook Colliery in a
Multiseam Environment
William LawrenceGeowork Engineering
BBUGS Blackwater February 2011 - Recent secondary extraction experience at Cook Colliery in a multi-seam environment
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Castor Seam Workings
BBUGS Blackwater February 2011 - Recent secondary extraction experience at Cook Colliery in a multi-seam environment
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Argo Seam Workings (Castor superimposed)
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Argo Seam Major Structure
N
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Lithology
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CMRR – South Argo
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CMRR – North Argo
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North Argo – 305 Panel
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Continuous Haulage System
• ABM25 with nominal 5.5 m x 3.8 m roadway profile
• Flexiveyor continuous haulage
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Roadway Development Authority To Mine
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Trigger Action Response Plan (TARP)
Triggers Level 1 Code Green/Grey/Purple Level 2 Code Yellow Level 3 Code Blue Level 4 Code Red
Roof Conditions
No delamination or slabbing of immediate roof in unsupported cutout
Joints or structure with no disturbed strata
Solid ring when sounding roof Dry conditions or isolated
drippers No partings while drilling holes Bolts installed to standard and
tensioned after recommended chemical set time
No weight showing on roof bolt plates
Roadway width >5.5 m Normal isolated and localised
delamination or slabbing of roof in unsupported cutout
Centreline crack forming above or behind miner in Level 1 support
Greasy surface in the roof Solid ring when sounding roof Dry conditions or isolated drippers No partings while drilling holes Bolts installed to standard and
tensioned after recommended chemical set time
No weight showing on roof bolt plates
Dry conditions or isolated drippers
Roadway width >6 m Persistent and extensive roof
slabbing in unsupported cutout, particularly if greasy surfaces are exposed
Dull or drummy sound when sounding roof
Open or infilled structure Near-vertical (>70°) fault, dyke
or shear with no disturbed strata
Partings within bolt horizon while drilling holes
Bolt chemical slower to go off and bolt taking longer to tension
Initiation of roof cracking or guttering
Wet roof or numerous localised drippers
Roadway width >6.5 m Fall of roof material >300 mm
in unsupported cut-out Any fault, dyke or shear with
disturbed strata, or mid to low-angled (<70°) structure
Open or infilled structure in intersection
Soft strata repeatedly bogging drill bits
Initial and replacement bolt not tensioning
Roof cracking or guttering not controlled by Level 3 support
Weight showing on roof supports and plates
Water seeping from roof or extensive drippers
Wet roof or numerous drippers in intersection
Rib Conditions
Normal cleat orientation and density, ie no noticeable change in rib conditions
Cleat is not near-parallel (>10°) to roadway
No other structure such as rib slip planes (leaners)
No rib spall at face or alongside continuous miner
Solid ring when sounding rib
Normal cleat orientation and density, ie no noticeable change in rib conditions
Cleat is not near-parallel (>10°) to roadway
No other structure such as rib slip planes (leaners)
No rib spall at face or alongside continuous miner
Leaner identified in face or rib Deterioration in rib conditions
after development, due to change in cleat, seam dip, stress, overlying workings, etc.
Cleat near-parallel (<10°) to roadway
Bar-down slabby rib as required
Any rib slip or fall of rib at face or alongside continuous miner
Persistent rib spall between bolts alongside continuous miner not controlled by Level 3 support
Monitoring Triggers
Tell-tale movement <15 mm, total Tell-tale movement <15 mm, total Tell-tale movement >15 mm,
total Tell-tale movement >40 mm,
total
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Method of Secondary Extraction
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Strata Conditions After Sumping
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Pillar Design
Primarily Empirical
• UNSW empirical pillar strength formulation
• Minimum remnant pillar FoS of 1.5
• Fenders do not contribute to pillar strength
• Assume pillar side has been stripped
• Fender stability can not be assessed using this empirical formula
Numerical modelling also required for certain situations
• Odd shaped pillars• Castor abutment• Extent of roof falls• Relatively simple models
are usually sufficient
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Displacement Discontinuity Numerical Modelling (LaModel)
Vertical pillar stress with no overlying Castor workings
Vertical pillar stress with overlying Castor workings
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Finite Element Numerical Modelling (Phase2)
Castor Seam
Argo Seam
10 m wide excavation
Plane of symmetry
Height ofpotential fall
2015
105
0-5
-10
0 5 10 15 20
Castor Seam
Argo Seam
14 m wide excavation
2015
105
0-5
-10
0 5 10 15 20
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Fender and Roadway Stability
General comments• Sumping can be done under poor roof conditions if primary
support is installed to TARP standard• This includes fault-affected strata and Castor abutment• However, sump spacing is increased under known faults and
Castor abutment• Some areas are just avoided!• Cleat orientation does affect fender stability• Generally, a “double-whammy” is avoided, e.g. fault and
Castor abutment• Falls may occur in unsupported sumps
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Sump Spacing (Fender Width) Design
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Secondary Extraction Roof Stability Issues
• Sump spacing design chart is a hybrid empirical and numerical method based on Cook experience.
• Yes, there has been inbye supported roadway roof falls of no consequence before it became an issue. These provide excellent data points.
• Even with the design chart there is no guarantee of inbye roadway stability after secondary extraction. Additional coal is being taken without supplementary support. Argo roof is relatively weak.
• Stability around the current sump must be ensured, and protocols (TARP) are in place for this. The crew must not take or complete a sump if conditions change.
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Recent KM02 Roof Falls
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KM02 C16/17 Fall
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KM02 D19/20 Fall
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Sump width
MRS
Caving
Sealed Castor
workings
FLAC3D
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FLAC3D model
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First workings in
Argo Seam – 6 m roadway
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Secondary extraction – 4 m sump and 7 m fender
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Secondary extraction –
16 m sump/strip with 8 m
fender
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First workings in Argo Seam
beneath Castor
roadways
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Secondary extraction –
16 m sump/strip with 8 m
fender
