2
as reserves with thicker parting, thinning coal seams, and
challenging conditions are encountered.
Recent advancements in computational modeling, par-
ticularly the LaModel program, have provided researchers
and engineers with tools to analyze pillar performance with
greater accuracy. However, the calibration of such models
remains a challenge, often requiring extensive field data and
iterative adjustments. The importance of accurate model
calibration cannot be overstated, as it can directly impact
the safety of mining operations.
This study, conducted at the Maple Eagle Mine in
Southern West Virginia, aims to bridge the gap between
theoretical modeling and real-world pillar behavior. By
leveraging state-of-the-art instrumentation and meticulous
data collection, this research seeks to calibrate the LaModel
program to the specific conditions of the Eagle Seam.
Furthermore, the study delves into the intricacies of pillar
behavior, exploring the impact of in-seam partings on coal
pillar strength.
Historically, coal pillar design software such as the
Analysis of Retreat Mining Pillar Stability (ARMPS) 2010
recommends a reduction of the entry height when com-
petent rock is being mined. It specifically states that “the
thickness of such ‘cap rock’ should be reduced by 50%
(Mark, 2010).” The definition of what is considered com-
petent rock, however, remains ambiguous.
In the sections that follow, a detailed account of the
instrumentation strategy employed at the Maple Eagle
Mine, the challenges faced during data collection, the cali-
bration process of the LaModel program, and the insights
derived from the analysis are provided. Through this com-
prehensive exploration, the aim of this study is to deter-
mine what, if any, of the in-seam parting can be considered
competent and, therefore be applicable to the 50% Rule.
MINE LAYOUT AND GEOLOGY
The Maple Eagle Mine, situated in Southern West Virginia,
extracts coal from the Eagle Seam at an average depth of
cover of approximately 600 ft. over the designated study
panel. The panel was designed as a nine-entry system with
pillars spaced on 80-ft by 120-ft centers, resulting in a total
panel width of 660 ft., excluding leave blocks. These are
coal pillars that are developed but intentionally left in place
during retreat mining.
Detailed near-seam geologic data was collected via
underground measurements and borescoping at the study
sites. The thickness of the in-seam parting in this area
ranged from 51 to 52 in. but varied somewhat in its com-
position. Roof geology data obtained from a 20-ft. borehole
indicated the first 13 ft. of immediate roof to be sandstone
with the remaining 7 ft. deemed indeterminate due to the
inability to clean the hole beyond this depth (See Figure 1).
More detailed information on the mine layout and geology
can be found in McElhinney, et al., 2023 which provides a
robust foundation for this study.
INSTRUMENTATION
Within the wrap-around bleeder system, three instrumen-
tation sites were strategically positioned to measure the rear
abutment loading, side abutment loading, and pillar per-
formance (McElhinney et al., 2023). Site 1 was situated
in the #4 entry, between crosscuts 30 and 31, at a depth of
cover of 550 ft.
Sites 2 and 3 were placed in the #1 Entry, between
crosscuts 20 and 21 and 18 and 19, with respective depths
of cover of 400 ft. and 500 ft. (See Figure 2).
In this study, the focus of attention will be on the anal-
ysis of data collected from borehole pressure cells (BPCs)
installed at the three distinct field sites. The data gathered
from these BPCs will be instrumental in understanding the
pillar performance in the mine. The use of extensometers,
while part of the broader instrumentation strategy, will not
be discussed in this paper. For detailed information on the
instrumentation used and best practices for installation see
Minoski et al. (2024) and McElhinney et al. (2024).
Figure 1. Coal section depicted as a composite of the
measurements obtained from the study area (after
McElhinney et al., 2023).
as reserves with thicker parting, thinning coal seams, and
challenging conditions are encountered.
Recent advancements in computational modeling, par-
ticularly the LaModel program, have provided researchers
and engineers with tools to analyze pillar performance with
greater accuracy. However, the calibration of such models
remains a challenge, often requiring extensive field data and
iterative adjustments. The importance of accurate model
calibration cannot be overstated, as it can directly impact
the safety of mining operations.
This study, conducted at the Maple Eagle Mine in
Southern West Virginia, aims to bridge the gap between
theoretical modeling and real-world pillar behavior. By
leveraging state-of-the-art instrumentation and meticulous
data collection, this research seeks to calibrate the LaModel
program to the specific conditions of the Eagle Seam.
Furthermore, the study delves into the intricacies of pillar
behavior, exploring the impact of in-seam partings on coal
pillar strength.
Historically, coal pillar design software such as the
Analysis of Retreat Mining Pillar Stability (ARMPS) 2010
recommends a reduction of the entry height when com-
petent rock is being mined. It specifically states that “the
thickness of such ‘cap rock’ should be reduced by 50%
(Mark, 2010).” The definition of what is considered com-
petent rock, however, remains ambiguous.
In the sections that follow, a detailed account of the
instrumentation strategy employed at the Maple Eagle
Mine, the challenges faced during data collection, the cali-
bration process of the LaModel program, and the insights
derived from the analysis are provided. Through this com-
prehensive exploration, the aim of this study is to deter-
mine what, if any, of the in-seam parting can be considered
competent and, therefore be applicable to the 50% Rule.
MINE LAYOUT AND GEOLOGY
The Maple Eagle Mine, situated in Southern West Virginia,
extracts coal from the Eagle Seam at an average depth of
cover of approximately 600 ft. over the designated study
panel. The panel was designed as a nine-entry system with
pillars spaced on 80-ft by 120-ft centers, resulting in a total
panel width of 660 ft., excluding leave blocks. These are
coal pillars that are developed but intentionally left in place
during retreat mining.
Detailed near-seam geologic data was collected via
underground measurements and borescoping at the study
sites. The thickness of the in-seam parting in this area
ranged from 51 to 52 in. but varied somewhat in its com-
position. Roof geology data obtained from a 20-ft. borehole
indicated the first 13 ft. of immediate roof to be sandstone
with the remaining 7 ft. deemed indeterminate due to the
inability to clean the hole beyond this depth (See Figure 1).
More detailed information on the mine layout and geology
can be found in McElhinney, et al., 2023 which provides a
robust foundation for this study.
INSTRUMENTATION
Within the wrap-around bleeder system, three instrumen-
tation sites were strategically positioned to measure the rear
abutment loading, side abutment loading, and pillar per-
formance (McElhinney et al., 2023). Site 1 was situated
in the #4 entry, between crosscuts 30 and 31, at a depth of
cover of 550 ft.
Sites 2 and 3 were placed in the #1 Entry, between
crosscuts 20 and 21 and 18 and 19, with respective depths
of cover of 400 ft. and 500 ft. (See Figure 2).
In this study, the focus of attention will be on the anal-
ysis of data collected from borehole pressure cells (BPCs)
installed at the three distinct field sites. The data gathered
from these BPCs will be instrumental in understanding the
pillar performance in the mine. The use of extensometers,
while part of the broader instrumentation strategy, will not
be discussed in this paper. For detailed information on the
instrumentation used and best practices for installation see
Minoski et al. (2024) and McElhinney et al. (2024).
Figure 1. Coal section depicted as a composite of the
measurements obtained from the study area (after
McElhinney et al., 2023).