4
from the setting pressure. The onset of sustained BPC pres-
surization began when mining was nearing completion of
the row directly inby the instrumentation site. Significant
pressurization began when slabbing of the instrumented
pillar began. Once the peak stress in the pillar was reached,
the pillar exhibited strain-softening behavior and began to
shed load onto the adjacent abutments (see Figure 7).
Site 3 showed similar performance to Site 2, with
some additional loss of data due to presumed damage to
the instrument or wiring. The onset of initial movement
was more difficult to determine here. However, all installed
BPCs began to show sustained pressurization when mining
was closing out in the row inby the instrumentation site. A
significant pressure increase began when active mining of
the instrumented pillar began. Once the peak stress in the
pillar was reached, the pillar began to shed load onto the
surrounding abutments (See Figure 8).
Based on the data collected from Sites 2 and 3 indicat-
ing the arrival of the front abutment loading, the abutment
distance was measured to be approximately 200 ft. Taking
the timing of the average peak pressure for the two pillars,
respectively, indicated that pillar yield began when the pil-
lar line was approximately 290 ft. outby the instrumenta-
tion site (see Figure 9). Having provided a comprehensive
summary of the data collected from the three sites, we now
Figure 6. BPC data collected from Site 1 with the solid
black line indicating the retreat mining start date and the
dashed black line indicating the date when the panel was
approximately squared up (after McElhinney et al., 2023).
Figure 7. BPC data collected from Site 2 during retreat
mining where the solid black line indicates initial movement,
and the increasingly smaller dashed lines indicate slabbing
of the instrumented pillar, the peak stress, and the near
completion of load shedding, respectively (after McElhinney
et al., 2023).
Figure 8. BPC data collected from Site 3 during retreat
mining where the solid black line indicates initial movement,
and the increasingly smaller dashed lines indicate slabbing
of the instrumented pillar and the peak stress, respectively
(after McElhinney et al., 2023).
from the setting pressure. The onset of sustained BPC pres-
surization began when mining was nearing completion of
the row directly inby the instrumentation site. Significant
pressurization began when slabbing of the instrumented
pillar began. Once the peak stress in the pillar was reached,
the pillar exhibited strain-softening behavior and began to
shed load onto the adjacent abutments (see Figure 7).
Site 3 showed similar performance to Site 2, with
some additional loss of data due to presumed damage to
the instrument or wiring. The onset of initial movement
was more difficult to determine here. However, all installed
BPCs began to show sustained pressurization when mining
was closing out in the row inby the instrumentation site. A
significant pressure increase began when active mining of
the instrumented pillar began. Once the peak stress in the
pillar was reached, the pillar began to shed load onto the
surrounding abutments (See Figure 8).
Based on the data collected from Sites 2 and 3 indicat-
ing the arrival of the front abutment loading, the abutment
distance was measured to be approximately 200 ft. Taking
the timing of the average peak pressure for the two pillars,
respectively, indicated that pillar yield began when the pil-
lar line was approximately 290 ft. outby the instrumenta-
tion site (see Figure 9). Having provided a comprehensive
summary of the data collected from the three sites, we now
Figure 6. BPC data collected from Site 1 with the solid
black line indicating the retreat mining start date and the
dashed black line indicating the date when the panel was
approximately squared up (after McElhinney et al., 2023).
Figure 7. BPC data collected from Site 2 during retreat
mining where the solid black line indicates initial movement,
and the increasingly smaller dashed lines indicate slabbing
of the instrumented pillar, the peak stress, and the near
completion of load shedding, respectively (after McElhinney
et al., 2023).
Figure 8. BPC data collected from Site 3 during retreat
mining where the solid black line indicates initial movement,
and the increasingly smaller dashed lines indicate slabbing
of the instrumented pillar and the peak stress, respectively
(after McElhinney et al., 2023).