6
improved pillar stability by transitioning from the tradi-
tional 4-Entry layout to the proposed 3-Entry Y-Y layout.
In both the first and second-panel mining scenarios,
the 3-Entry Y-Y layout consistently outperformed the
other designs, reducing stress. After first panel mining, the
3-Entry Y-Y configuration achieved a 19% reduction in the
average stress across the 4-Entry abutment pillar and a 5%
reduction in the average stress across the barrier compared
to the 3-Entry Y-A layout, with notable improvements
observed on the far side of the barrier in the subsequent
tailgate where floor instability was observed. Similarly, after
second-panel mining, the 3-Entry Y-Y layout exhibited a
22% reduction in stress across the abutment/barrier pillar
compared to the 4-Entry configuration and an 8% reduc-
tion compared to the 3-Entry Y-A layout. These reductions
indicate that the 3-Entry Y-Y design provides a more bal-
anced and efficient load distribution, potentially decreasing
the risks of mining-induced seismicity.
The safety factor analysis of the barrier/abutment pillar
is most critical considering isolated loading conditions fol-
lowing second-panel mining. In this scenario, the 3-Entry
Y-Y configuration achieved a barrier pillar safety factor of
2.2, compared to the 4-Entry layout and the 3-Entry Y-A
layout with safety factors of 1.1 and 1.6, respectively. This
substantial increase in safety factor indicates the 3-Entry
Y-Y layout’s superior ability to maintain pillar integrity
under the most demanding conditions, ensuring greater
long-term stability. These findings underscore the potential
of the 3-Entry Y-Y design to help mitigate the risks associ-
ated with mining-induced seismicity, offering a potential
solution for maintaining structural integrity in wider panel
configurations and deeper cover environments.
LIMITATIONS AND FUTURE RESEARCH
While this study provides valuable insights into gateroad
pillar stability under deep-cover mining conditions, it is
essential to acknowledge certain limitations. First, the anal-
ysis is based on a single case history from a specific longwall
mine in Southwestern Virginia. As a result, the findings,
while indicative, may not be representative of all mining
operations or geological settings. Variations in geologi-
cal conditions, overburden properties, and mining depths
can significantly affect the performance of gateroad pillar
layouts, and further studies are necessary to validate these
results across a wider range of mines and conditions.
Despite some identified challenges, the previous
4-Entry yield-abutment-yield design was largely successful
in maintaining stability over many years of operation. The
issues observed in the current 3-Entry Y-A layout, such as
floor heave, may not be solely attributed to the pillar design
but could also be influenced by factors such as panel width
and evolving geological conditions. When interpreting the
results, this context should be considered, particularly when
recommending future pillar design modifications.
0
0.5
1
1.5
2
2.5
3
3.5
0 100 200 300 400 500
Pillar Stress Safety Factors -First Panel
4-Entry
3-Entry Y-A
3-Entry Y-Y
Figure 8. Safety factors of the gateroad pillars after first-panel mining for the three scenarios
PillarStress
Safety
Factor
improved pillar stability by transitioning from the tradi-
tional 4-Entry layout to the proposed 3-Entry Y-Y layout.
In both the first and second-panel mining scenarios,
the 3-Entry Y-Y layout consistently outperformed the
other designs, reducing stress. After first panel mining, the
3-Entry Y-Y configuration achieved a 19% reduction in the
average stress across the 4-Entry abutment pillar and a 5%
reduction in the average stress across the barrier compared
to the 3-Entry Y-A layout, with notable improvements
observed on the far side of the barrier in the subsequent
tailgate where floor instability was observed. Similarly, after
second-panel mining, the 3-Entry Y-Y layout exhibited a
22% reduction in stress across the abutment/barrier pillar
compared to the 4-Entry configuration and an 8% reduc-
tion compared to the 3-Entry Y-A layout. These reductions
indicate that the 3-Entry Y-Y design provides a more bal-
anced and efficient load distribution, potentially decreasing
the risks of mining-induced seismicity.
The safety factor analysis of the barrier/abutment pillar
is most critical considering isolated loading conditions fol-
lowing second-panel mining. In this scenario, the 3-Entry
Y-Y configuration achieved a barrier pillar safety factor of
2.2, compared to the 4-Entry layout and the 3-Entry Y-A
layout with safety factors of 1.1 and 1.6, respectively. This
substantial increase in safety factor indicates the 3-Entry
Y-Y layout’s superior ability to maintain pillar integrity
under the most demanding conditions, ensuring greater
long-term stability. These findings underscore the potential
of the 3-Entry Y-Y design to help mitigate the risks associ-
ated with mining-induced seismicity, offering a potential
solution for maintaining structural integrity in wider panel
configurations and deeper cover environments.
LIMITATIONS AND FUTURE RESEARCH
While this study provides valuable insights into gateroad
pillar stability under deep-cover mining conditions, it is
essential to acknowledge certain limitations. First, the anal-
ysis is based on a single case history from a specific longwall
mine in Southwestern Virginia. As a result, the findings,
while indicative, may not be representative of all mining
operations or geological settings. Variations in geologi-
cal conditions, overburden properties, and mining depths
can significantly affect the performance of gateroad pillar
layouts, and further studies are necessary to validate these
results across a wider range of mines and conditions.
Despite some identified challenges, the previous
4-Entry yield-abutment-yield design was largely successful
in maintaining stability over many years of operation. The
issues observed in the current 3-Entry Y-A layout, such as
floor heave, may not be solely attributed to the pillar design
but could also be influenced by factors such as panel width
and evolving geological conditions. When interpreting the
results, this context should be considered, particularly when
recommending future pillar design modifications.
0
0.5
1
1.5
2
2.5
3
3.5
0 100 200 300 400 500
Pillar Stress Safety Factors -First Panel
4-Entry
3-Entry Y-A
3-Entry Y-Y
Figure 8. Safety factors of the gateroad pillars after first-panel mining for the three scenarios
PillarStress
Safety
Factor