10
seam under 352-m cover. Two boreholes were drilled above
an abutment pillar in the mine. Slug permeability measure-
ment tests were conducted in the boreholes at two perfo-
ration intervals located in the Sewickley and Uniontown
horizons. A modeling methodology previously developed
by researchers at the National Institute for Occupational
Safety and Health (NIOSH) was used to investigate the
fracture propagation and aperture changes due to mining.
It was shown that the minimum aperture values are located
in an area above the abutment pillar from the mine roof to
120 m above. The results show that the modeling approach
can be used to predict permeability values in similar mining
and geologic conditions. Future work can quantify the
effects of geological parameters, mining layout, and over-
burden depth on the fracture aperture evolution and its
effects on the rockmass permeability.
LIMITATIONS
This study shows that the field measurement of permeability
altered by mining agrees well with the modeling results for
a deep cover longwall mine in Southwestern Pennsylvania.
However, further work is required to validate the proposed
modeling methodology in different geology and operation
settings.
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
0.00001 0.01 10
Permeability (Darcy)
First panel mined
Bedding planes
Sub Vertical fractures
Measured
Coal
(a)
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
0.00001 0.01 10
Permeability (Darcy)
Second panel mined
Bedding planes
Sub Vertical fractures
Measured
Coal
(b)
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
0.00001 0.01 10
Permeability (Darcy)
Third panel mined
Bedding planes
Sub Vertical fractures
Coal
(c)
Figure 12. Results of modeled and measured permeability along the depth for (a) first panel is mined, (b) second panel is
mined, and (c) third panel is mined
Table 2. Field measurements and model predictions of permeabilities
Sewickley Uniontown
Model Field** Model Field
SV BP — SV BP —
First panel mined 1.4 mD 20.6 D 1.03 mD 0.9 mD 17.7 D 0.19 mD
Second panel mined 1.4 mD 0.14 mD 0.09 mD 2.9 mD 0.1 mD 0.12 mD
Third panel mined 1.9 mD 0.2 mD — 2.27 mD 0.15 mD —
SV: subvertical fractures BP: Bedding planes Field: Slug test measurement results
Depth,
m Depth,
m Depth,
m
seam under 352-m cover. Two boreholes were drilled above
an abutment pillar in the mine. Slug permeability measure-
ment tests were conducted in the boreholes at two perfo-
ration intervals located in the Sewickley and Uniontown
horizons. A modeling methodology previously developed
by researchers at the National Institute for Occupational
Safety and Health (NIOSH) was used to investigate the
fracture propagation and aperture changes due to mining.
It was shown that the minimum aperture values are located
in an area above the abutment pillar from the mine roof to
120 m above. The results show that the modeling approach
can be used to predict permeability values in similar mining
and geologic conditions. Future work can quantify the
effects of geological parameters, mining layout, and over-
burden depth on the fracture aperture evolution and its
effects on the rockmass permeability.
LIMITATIONS
This study shows that the field measurement of permeability
altered by mining agrees well with the modeling results for
a deep cover longwall mine in Southwestern Pennsylvania.
However, further work is required to validate the proposed
modeling methodology in different geology and operation
settings.
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
0.00001 0.01 10
Permeability (Darcy)
First panel mined
Bedding planes
Sub Vertical fractures
Measured
Coal
(a)
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
0.00001 0.01 10
Permeability (Darcy)
Second panel mined
Bedding planes
Sub Vertical fractures
Measured
Coal
(b)
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
0.00001 0.01 10
Permeability (Darcy)
Third panel mined
Bedding planes
Sub Vertical fractures
Coal
(c)
Figure 12. Results of modeled and measured permeability along the depth for (a) first panel is mined, (b) second panel is
mined, and (c) third panel is mined
Table 2. Field measurements and model predictions of permeabilities
Sewickley Uniontown
Model Field** Model Field
SV BP — SV BP —
First panel mined 1.4 mD 20.6 D 1.03 mD 0.9 mD 17.7 D 0.19 mD
Second panel mined 1.4 mD 0.14 mD 0.09 mD 2.9 mD 0.1 mD 0.12 mD
Third panel mined 1.9 mD 0.2 mD — 2.27 mD 0.15 mD —
SV: subvertical fractures BP: Bedding planes Field: Slug test measurement results
Depth,
m Depth,
m Depth,
m