8
CONCLUSIONS
This comprehensive study, conducted at the Maple Eagle
Mine in Southern West Virginia, has provided valuable
insights into the behavior of pillars and the calibration of
the LaModel program. The following conclusions can be
drawn:
Instrumentation and Data Collection: The strategic
placement of borehole pressure cells (BPCs) at three differ-
ent sites within the mine as detailed in McElhinney et al.,
2023 allowed for a detailed understanding of pillar perfor-
mance. The data collected from these sites was instrumen-
tal in calibrating the LaModel program, providing a robust
foundation for further analysis.
Model Calibration: The calibration of the LaModel pro-
gram involved meticulous adjustments of critical param-
eters such as Rock Mass Stiffness, Gob Stiffness, and Coal
Strength. The alignment of these parameters with the
measured data ensured the accuracy of the stress and load
calculations.
Virtual Mining Height Adjustment: The adjustment of
the virtual mining height to match the timing of peak stress
measured in the field was a critical step in the calibration
process. The reduction of the mining height to 7.5 ft. for
Site 2 and 7 ft. for Site 3 resulted in an average reduction
of the shale parting thickness of 52%—which means that
the “50% Rule” is applicable for the shale parting observed
at these sites.
Model Results and Correlation: The calibrated model
exhibited an excellent correlation with the measured data
from Sites 2 and 3. The repeatability of results between
these sites further validated the model’s accuracy.
In summary, the research conducted in this study rep-
resents a significant contribution to the field of pillar design
and numerical model calibration. This study represents
the first successful measurement of the “50% Rule” and
the impact of a thick in-seam parting on pillar strength.
The insights gained from this study not only enhance our
understanding of pillar behavior but also pave the way for
future research and innovation in mine safety.
LIMITATIONS AND FUTURE RESEARCH
The primary limitation of this study is the limited scope
of potential application, because this study reports on site-
specific findings, the findings may not be directly applica-
ble to mines with different geological conditions. Research
is ongoing at the mine to take a second measurement of the
pillar performance in a subsequent panel where the in-seam
parting is thinner and apparently weaker.
Additional limitations refer to assumptions made in
the study, such as the alignment of the peak stress in the
pillar with the expected values from the Bieniawski stress
gradient. While this assumption currently represents our
most thorough understanding of pillar strength and assists
with making comparisons to modern pillar stability analy-
sis tools, it might not hold true in all mining scenarios,
limiting the applicability of the calibration method.
Finally, the study refers to the ambiguity in defining
what is considered competent rock. This ambiguity could
lead to variations in the application of the “50% rule.” This
could impact the replicability of the study in different con-
texts, mining scenarios, and geologic conditions.
Future research in relation to the “50% Rule” and
the impact of in-seam parting on pillar strength would be
required to address these limitations. This should include
additional field sites to measure pillar performance with
a range of geologic conditions including rock thickness
and strength. Additional data should be collected on the
strength of the parting itself to better define what should
and should not be considered competent rock. Research
such as this would provide engineers with a much more
broadly applicable tool for assessing the strength of coal pil-
lars as more mines experience significant out-of-seam dilu-
tion and are mining more rock.
In conclusion, while the study provides valuable
insights into the behavior of pillars in a specific mining
context, the limitations must be considered when applying
the findings to other scenarios. The implications for future
research highlight exciting opportunities for further explo-
ration and development in the field of coal pillar design.
DISCLAIMER
The findings and conclusions in this report are those of
the authors and do not necessarily represent the official
position of the National Institute for Occupational Safety
and Health, Centers for Disease Control and Prevention.
Mention of any company or product does not constitute
endorsement by NIOSH.
REFERENCES
Babcock, C.O. (1986). “Equations for the Analysis of
Borehole Pressure Cell Data.” In Proceedings of the
27th US Symposium on Rock Mechanics. Tuscaloosa,
AL. pp. 233–240.
Bauer, E.R., Ghekan, G.J., and Hill III, J.C. (1985). “A
Borehole Pressure Instrument for Measuring Mining-
Induced Pressure Changes in Underground Coal
Mines.” In Proceedings of the 26th US Symposium on
Rock Mechanics. Rapid City, SD. pp. 1075–1084.
Heasley, K. (2008). “Some Thoughts on Calibrating
LaModel.” In proceedings of the 27th International
CONCLUSIONS
This comprehensive study, conducted at the Maple Eagle
Mine in Southern West Virginia, has provided valuable
insights into the behavior of pillars and the calibration of
the LaModel program. The following conclusions can be
drawn:
Instrumentation and Data Collection: The strategic
placement of borehole pressure cells (BPCs) at three differ-
ent sites within the mine as detailed in McElhinney et al.,
2023 allowed for a detailed understanding of pillar perfor-
mance. The data collected from these sites was instrumen-
tal in calibrating the LaModel program, providing a robust
foundation for further analysis.
Model Calibration: The calibration of the LaModel pro-
gram involved meticulous adjustments of critical param-
eters such as Rock Mass Stiffness, Gob Stiffness, and Coal
Strength. The alignment of these parameters with the
measured data ensured the accuracy of the stress and load
calculations.
Virtual Mining Height Adjustment: The adjustment of
the virtual mining height to match the timing of peak stress
measured in the field was a critical step in the calibration
process. The reduction of the mining height to 7.5 ft. for
Site 2 and 7 ft. for Site 3 resulted in an average reduction
of the shale parting thickness of 52%—which means that
the “50% Rule” is applicable for the shale parting observed
at these sites.
Model Results and Correlation: The calibrated model
exhibited an excellent correlation with the measured data
from Sites 2 and 3. The repeatability of results between
these sites further validated the model’s accuracy.
In summary, the research conducted in this study rep-
resents a significant contribution to the field of pillar design
and numerical model calibration. This study represents
the first successful measurement of the “50% Rule” and
the impact of a thick in-seam parting on pillar strength.
The insights gained from this study not only enhance our
understanding of pillar behavior but also pave the way for
future research and innovation in mine safety.
LIMITATIONS AND FUTURE RESEARCH
The primary limitation of this study is the limited scope
of potential application, because this study reports on site-
specific findings, the findings may not be directly applica-
ble to mines with different geological conditions. Research
is ongoing at the mine to take a second measurement of the
pillar performance in a subsequent panel where the in-seam
parting is thinner and apparently weaker.
Additional limitations refer to assumptions made in
the study, such as the alignment of the peak stress in the
pillar with the expected values from the Bieniawski stress
gradient. While this assumption currently represents our
most thorough understanding of pillar strength and assists
with making comparisons to modern pillar stability analy-
sis tools, it might not hold true in all mining scenarios,
limiting the applicability of the calibration method.
Finally, the study refers to the ambiguity in defining
what is considered competent rock. This ambiguity could
lead to variations in the application of the “50% rule.” This
could impact the replicability of the study in different con-
texts, mining scenarios, and geologic conditions.
Future research in relation to the “50% Rule” and
the impact of in-seam parting on pillar strength would be
required to address these limitations. This should include
additional field sites to measure pillar performance with
a range of geologic conditions including rock thickness
and strength. Additional data should be collected on the
strength of the parting itself to better define what should
and should not be considered competent rock. Research
such as this would provide engineers with a much more
broadly applicable tool for assessing the strength of coal pil-
lars as more mines experience significant out-of-seam dilu-
tion and are mining more rock.
In conclusion, while the study provides valuable
insights into the behavior of pillars in a specific mining
context, the limitations must be considered when applying
the findings to other scenarios. The implications for future
research highlight exciting opportunities for further explo-
ration and development in the field of coal pillar design.
DISCLAIMER
The findings and conclusions in this report are those of
the authors and do not necessarily represent the official
position of the National Institute for Occupational Safety
and Health, Centers for Disease Control and Prevention.
Mention of any company or product does not constitute
endorsement by NIOSH.
REFERENCES
Babcock, C.O. (1986). “Equations for the Analysis of
Borehole Pressure Cell Data.” In Proceedings of the
27th US Symposium on Rock Mechanics. Tuscaloosa,
AL. pp. 233–240.
Bauer, E.R., Ghekan, G.J., and Hill III, J.C. (1985). “A
Borehole Pressure Instrument for Measuring Mining-
Induced Pressure Changes in Underground Coal
Mines.” In Proceedings of the 26th US Symposium on
Rock Mechanics. Rapid City, SD. pp. 1075–1084.
Heasley, K. (2008). “Some Thoughts on Calibrating
LaModel.” In proceedings of the 27th International