1
24-004
A Study on the Impact of In-Seam Rock Partings on Coal
Pillar Strength Based on Field Instrumentation and Numerical
Modeling at the Maple Eagle Mine
Morgan M. Sears
CDC NIOSH, Pittsburgh, PA
Mark Morris
Blackhawk Mining, LLC., Charleston, WV
Joseph Bright
Blackhawk Mining, LLC., Charleston, WV
ABSTRACT
In an effort to advance the science underlying modern coal
pillar stability analysis, researchers at the National Institute
for Occupational Safety and Health are currently involved
in research aimed at better understanding the impact of an
in-seam rock parting on the strength of coal pillars. The
purpose of this study is to determine a suitable virtual min-
ing height that could be applied using current pillar stabil-
ity analysis tools. To accomplish this, the boundary element
model LaModel was used to back analyze data collected on
pillar performance in a room-and-pillar panel at the Maple
Eagle Mine located in Southern West Virginia.
In a previous work, data collected from borehole pres-
sure cells (BPCs) and extensometers were taken from three
instrumentation sites. Data collected from the back bleed-
ers were used to measure the rear abutment stresses, and
data collected from two instrumentation sites in the wrap-
around bleeder were used to measure the front and side
abutment stresses as well as the peak strength and perfor-
mance of the slabbed leave pillar. The utilization of two
nearly identical instrumentation sites in the wrap-around
bleeder provided much needed repeatability of the obtained
measurements.
In this study, the data collected from BPCs at the
three instrumentation sites was calibrated to match the
Bieniawski pillar stress gradient. To model the measured
pillar behavior, the LaModel program was selected due to
its capability of being directly comparable to the Analysis
of Retreat Mining Pillar Stability (ARMPS) and Analysis
of Coal Pillar Stability (ACPS) programs. The model was
then calibrated to match the measured abutment extent
and abutment stress. Finally, the model was validated by
reducing the modeled mining height until the yielding of
the slabbed leave pillars in the model matched what was
measured in the field.
The final calibrated mining heights show that a reduc-
tion of the shale parting thickness, not including any clay
layers, of 52% is applicable. This research study provides
the first known measurement of the ARMPS/ACPS “50%
Rule” and its applicability to this panel of the Maple Eagle
Mine. This finding provides a proof of concept and could
have significant implications for future research.
INTRODUCTION
One of the primary challenges in underground coal mining
is ensuring the stability of the mine structure, particularly
the pillars that support the overlying strata. In the Central
Appalachian region, the unique geological formations are
complicated by factors such as varying depths of cover,
geological anomalies, and the presence of in-seam partings.
These complexities necessitate a thorough understand-
ing of pillar behavior under different mining conditions
24-004
A Study on the Impact of In-Seam Rock Partings on Coal
Pillar Strength Based on Field Instrumentation and Numerical
Modeling at the Maple Eagle Mine
Morgan M. Sears
CDC NIOSH, Pittsburgh, PA
Mark Morris
Blackhawk Mining, LLC., Charleston, WV
Joseph Bright
Blackhawk Mining, LLC., Charleston, WV
ABSTRACT
In an effort to advance the science underlying modern coal
pillar stability analysis, researchers at the National Institute
for Occupational Safety and Health are currently involved
in research aimed at better understanding the impact of an
in-seam rock parting on the strength of coal pillars. The
purpose of this study is to determine a suitable virtual min-
ing height that could be applied using current pillar stabil-
ity analysis tools. To accomplish this, the boundary element
model LaModel was used to back analyze data collected on
pillar performance in a room-and-pillar panel at the Maple
Eagle Mine located in Southern West Virginia.
In a previous work, data collected from borehole pres-
sure cells (BPCs) and extensometers were taken from three
instrumentation sites. Data collected from the back bleed-
ers were used to measure the rear abutment stresses, and
data collected from two instrumentation sites in the wrap-
around bleeder were used to measure the front and side
abutment stresses as well as the peak strength and perfor-
mance of the slabbed leave pillar. The utilization of two
nearly identical instrumentation sites in the wrap-around
bleeder provided much needed repeatability of the obtained
measurements.
In this study, the data collected from BPCs at the
three instrumentation sites was calibrated to match the
Bieniawski pillar stress gradient. To model the measured
pillar behavior, the LaModel program was selected due to
its capability of being directly comparable to the Analysis
of Retreat Mining Pillar Stability (ARMPS) and Analysis
of Coal Pillar Stability (ACPS) programs. The model was
then calibrated to match the measured abutment extent
and abutment stress. Finally, the model was validated by
reducing the modeled mining height until the yielding of
the slabbed leave pillars in the model matched what was
measured in the field.
The final calibrated mining heights show that a reduc-
tion of the shale parting thickness, not including any clay
layers, of 52% is applicable. This research study provides
the first known measurement of the ARMPS/ACPS “50%
Rule” and its applicability to this panel of the Maple Eagle
Mine. This finding provides a proof of concept and could
have significant implications for future research.
INTRODUCTION
One of the primary challenges in underground coal mining
is ensuring the stability of the mine structure, particularly
the pillars that support the overlying strata. In the Central
Appalachian region, the unique geological formations are
complicated by factors such as varying depths of cover,
geological anomalies, and the presence of in-seam partings.
These complexities necessitate a thorough understand-
ing of pillar behavior under different mining conditions