8
monitoring boreholes (Figure 10). The Uniontown and
Sewickley horizons both reached a maximum measured
permeability of 6.6 mD and 8.8 mD, respectively, before
decreasing again to 2 mD after the second LW mine-by.
Researchers were able to monitor the deep cover site
between LW panel mine-bys. Figure 11 shows the period
between the first and second LW panel mine-by. The per-
meability measurements during this time frame did not
change much at each horizon and remained at or below
their respective pre-mine-by values (shown in Figure 11) by
the green and grey horizontal lines. Table 2 lists the average
permeability values for the pre-, post‑1st LW panel, and
post 2nd LW panel mine-bys. The pre-mining values of
permeabilities at the Sewickley and Uniontown horizons
are close but VEP-S shows higher values although under
deeper cover. This might be related to the degree of bed-
ding and laminations at the Sewickley horizon. Evaluation
of mechanisms leading to high permeabilities showed that
bedding plane permeability is generally several orders of
magnitudes larger than the permeability of subvertical frac-
ture [15]. This is because the horizontal stress (perpendicu-
lar to the mining direction) in the Pittsburgh coal seam
Figure 10. Permeability measurements pre-, during, and post- second LW panel mine-by under deep cover.
Negative distances are the LW panel approaching the monitoring boreholes. VEP-U is at the Uniontown
horizon and VEP-S is at the Sewickley horizon
Figure 11. Permeability measurements pre-, during, and post- LW panel mine-by under deep cover
monitoring boreholes (Figure 10). The Uniontown and
Sewickley horizons both reached a maximum measured
permeability of 6.6 mD and 8.8 mD, respectively, before
decreasing again to 2 mD after the second LW mine-by.
Researchers were able to monitor the deep cover site
between LW panel mine-bys. Figure 11 shows the period
between the first and second LW panel mine-by. The per-
meability measurements during this time frame did not
change much at each horizon and remained at or below
their respective pre-mine-by values (shown in Figure 11) by
the green and grey horizontal lines. Table 2 lists the average
permeability values for the pre-, post‑1st LW panel, and
post 2nd LW panel mine-bys. The pre-mining values of
permeabilities at the Sewickley and Uniontown horizons
are close but VEP-S shows higher values although under
deeper cover. This might be related to the degree of bed-
ding and laminations at the Sewickley horizon. Evaluation
of mechanisms leading to high permeabilities showed that
bedding plane permeability is generally several orders of
magnitudes larger than the permeability of subvertical frac-
ture [15]. This is because the horizontal stress (perpendicu-
lar to the mining direction) in the Pittsburgh coal seam
Figure 10. Permeability measurements pre-, during, and post- second LW panel mine-by under deep cover.
Negative distances are the LW panel approaching the monitoring boreholes. VEP-U is at the Uniontown
horizon and VEP-S is at the Sewickley horizon
Figure 11. Permeability measurements pre-, during, and post- LW panel mine-by under deep cover