Anglo American PowerPoint template

1
Evaluating the Effectiveness of the 1750 Tonne
Shields at Moranbah North Mine
Kelly Martin Mehmet Kizil Ismet Canbulat
2
Outline

• Project background
• Project aims and scope
• Methodology
• Results of analysis
• Summary of results
• Conclusions

3
Project Background

• Challenging geotechnical environment historically
  resulted in cavity formation on the longwall face
  with its associated reduction in productivity
• Complex geology
• Depth
• Sandstone channels
• Faults
• Ply split and rider seam split
• Concerns raised about roof stability in future
  panels at greater depths
• Determined that 1750t shields would be required
  to adequately control strata

4
Project Background Continued

• 1750t shields are highest capacity shields in the
  world
• Replaced 980t shields due to
• Aging duty
• Supports operating at yield for significant
  periods
• Structural condition
• Increasing depths, complex geology and associated
  geotechnical conditions
• 1750t shields installed at start of LW108 panel

5
Project Aim and Scope
Aim

• To determine the effectiveness of the new 1750
  tonne shields

Scope

• Data analysis was confined to parallel sections
  of LW107 and LW108
• Panels are adjacent to each other and are subject
  to similar conditions
• Comparison of both panels using analysis results
  was used to determine effectiveness of 1750t
  shields
• Only data related to cavity development and
  strata control were analysed

6
Methodology

• LVA data sorted and converted into pressure
  contour maps
• Hazard map created using geological data and
  contour maps
• Identified and analysed
• Number of cavities in each panel
• Cavity occurrences in hazard zones
• Lost time due to strata control issues
• Lost time due to shield issues
• Percentage of time spent at or above yield
  pressure
• Percentage of time cavities were encountered in
  panel
• Data analysis supplemented by
• Deputy delay reports
• Fault maps
• Geological data

7
Leg Pressure Contours
LW107
LW108

• Converted LVA pressure and chainage data into
  real-time coordinates using Surfer
• Low pressure regions coloured red indicate
  cavities (lt250 bar)

8
Number of Low Pressure Regions
LW107 LW108
Total Number of Cavities with lost time 38 6
TG Cavities with lost time 4 4
Face Cavities with lost time 34 2
9
Geological Hazard Map
LW108
LW107
10
Cavities in Hazard Zones
Hazard Zone Number of Low Pressure Regions Number of Low Pressure Regions
Hazard Zone LW107 LW108
Fault Zone Multiple 0
Ply Split Zone Multiple 10
GMR Split Zone 9 1
GMR Split and Weighting Zone 6 3
Weighting Zone 41 1
11
Total Time Lost Due to Strata Control Issues

• 17 less lost time in LW108 due to strata control
  issues

12
Time Lost Due to Face Cavities

• 87 less lost time in LW108 due to face cavities

13
Time Lost Due to TG Cavities

• 82 more lost time in LW108 due to TG cavities

14
Lost Time Due to TG Cavities Continued
15
LW108 TG Issues and Delays

• Double stress notch encountered at point
  corresponding to LW107 install road
• Effects extended approx. 1 C/T (100m) into LW108
  panel
• Intense additional TG support required causing
  delays
• Large unmapped faults encountered perpendicular
  to face
• Led to major stoppages due to TG support issues
• Additional delays due to gas levels unique to
  LW108
• Prevented immediate entry to TG to install
  secondary support resulting in additional lost
  time
• The final analysis of shield effectiveness should
  subsequently only focus on strata control issues
  which occurred at the FACE in order to provide an
  accurate comparative assessment

16
Lost Time Due to Shield Issues

• 48 less lost time in LW108 due to shield issues

17
Shield Performance from LVA Data

• LW107
• Constant fluctuations in shield pressures
• Regularly operated at or above yield pressure
• Regularly operated at significantly low pressures
• Shields adjacent to cavity zones consistently in
  yield
• LW108
• Relatively consistent shield pressures
• Rarely operated in yield
• Even around cavity zones resulting in increased
  loading, the shields did not yield

18
Shield Performance Around Cavity Zones
Posi-set pressure (bar) 400
Yield pressure (bar) 450
19
Shield Performance Around Cavity Zones
Posi-set pressure (bar) 410
Yield pressure (bar) 465
20
Shield Performance From LVA Data
LW107 LW108
Percentage of time cavities were encountered in panel () 8.52 3.12
Percentage of time shields were at or above yield pressure () 6.47 0.61
21
Overall Performance Comparison
LW108 LW107
Number of Low Pressure regions 27 87
Time Lost (Face Cavities)(h) 20 148
Time Lost (Shields) (h) 314 603
Shield Rating in High Hazard Zones Moderate - High Low
Percentage of time cavities were encountered in panel () 3.12 8.52
Percentage of time shields were at or above yield pressure () 0.61 6.47
22
Based on an acceptable yield percentage value of
5
Shield Suitability

• LW107
• shields not suited to the mining conditions
• Shields spent 6.47 of time operating at or above
  yield pressure
• Total time spent in yield would actually be
  significantly higher
• LW108
• More than adequate for mining conditions
• Shields spent 0.61 operating at or above yield
  pressure
• Total time spent in yield would be significantly
  higher
• In future panels at greater depths and increased
  loading it is feasible to say that the 1750 tonne
  shields would be suitable to the conditions

23
Conclusions

• LW108 performed significantly better in
  geotechnical hazard zones
• Only 2 face cavities in LW108 with lost time
  compared with 34 in LW107
• Almost half the time lost due to shield issues in
  LW108
• 1750t shields found to be effective overall and
  more than adequate for mining conditions with
  greater potential for future panels

24
Anglo American Metallurgical Coal is acknowledged
with gratitude for the permission to publish this
paper. Steve Winter and Andrew Laws are thanked
for their willingness to share their knowledge
and for providing the necessary data for the
project.
25
Thank you