10
14.67 MPa at 0.2 m to 13.90 MPa at 0.5 m thickness. In
this case, dirt bands placed at the middle of the pillar yield
the highest strength, while roof-based dirt bands result
in lower strength due to the different stress distributions
encountered at this depth.
At 266 m (Figure 10(c), Table 6), increased dirt band
thickness reduces pillar strength from 15.83 MPa to
14.93 MPa, with the middle-positioned bands maintain-
ing the highest stability. Roof-positioned dirt bands, by
contrast, contribute to the lowest strength values, possibly
because of intensified stress near the roof at this depth. At
300 m (Figure 10(d), Table 7), the trend remains consis-
tent: pillar strength declines from 15.97 MPa at 0.2 m to
15.10 MPa at 0.5 m thickness, with middle-positioned
bands offering slightly better stability, while roof-based
bands show the lowest strength under the increasing stress.
For depths of 400 m (Figure 10(e), Table 8) and 500 m
(Figure 10(f), Table 9), the influence of dirt band thick-
ness on pillar strength is more pronounced. At 400 m, the
values decrease from 16.60 MPa to 15.67 MPa as thick-
ness increases from 0.2 m to 0.5 m. Pillars with middle
and floor-positioned bands maintain higher strength val-
ues than those with roof-positioned bands, where increased
stress levels near the roof amplify the adverse effect of
thicker dirt bands. At 500 m depth, thicker dirt bands
cause further weakening, with average strength reducing
from 16.97 MPa at 0.2 m thickness to 16.10 MPa at 0.5 m.
The slightly higher stability for middle-positioned bands
suggests some mitigation of stress concentration.
Overall, these results underscore the importance of
considering both thickness and placement of dirt bands
Table 4. Effect of dirt band thickness and location on pillar
strength at 100 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of Dirt Bed
Roof-
Interface Middle
Floor-
Interface
0.2 12.7 13.2 13.8 13.23
0.3 12.4 13.2 13.8 13.13
0.4 12 13 13.6 12.87
0.5 11.8 12.8 13.4 12.67
Table 5. Effect of dirt band thickness and location on pillar
strength at 200 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of Dirt Bed
Roof-
interface Middle
Floor-
interface
0.2 14 15.2 14.8 14.67
0.3 13.6 14.9 14.7 14.40
0.4 13.3 14.8 14.6 14.23
0.5 12.9 14.5 14.3 13.90
Table 6. Effect of dirt band thickness and location on pillar
strength at 266 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of Dirt Bed
Roof-
Interface Middle
Floor-
Interface
0.2 15.3 16.2 16 15.83
0.3 14.8 15.9 15.7 15.47
0.4 14.4 15.6 15.4 15.13
0.5 14.2 15.4 15.2 14.93
Table 7. Effect of dirt band thickness and location on pillar
strength at 300 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location Of Dirt Bed
Roof-
Interface Middle
Floor-
Interface
0.2 15.6 16.2 16.1 15.97
0.3 15.2 16 15.9 15.70
0.4 14.8 15.8 15.8 15.47
0.5 14.3 15.5 15.5 15.10
Table 8. Pillar strength affected by dirt band of varying
thickness at 400 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of Dirt Bed
Roof-
Interface Middle
Floor-
Interface
0.2 16.3 16.9 16.6 16.60
0.3 15.6 16.7 16.5 16.27
0.4 15.2 16.4 16.3 15.97
0.5 14.9 16.1 16 15.67
Table 9. Pillar strength affected by dirt band of varying
thickness at 500 m depth of cover
Thickness
of dirt
band
(m)
Pillar strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of dirt bed
Roof-
interface Middle
Floor-
interface
0.2 16.6 17.3 17 16.97
0.3 16 17 16.8 16.60
0.4 15.6 16.8 16.6 16.33
0.5 15.4 16.6 16.3 16.10
14.67 MPa at 0.2 m to 13.90 MPa at 0.5 m thickness. In
this case, dirt bands placed at the middle of the pillar yield
the highest strength, while roof-based dirt bands result
in lower strength due to the different stress distributions
encountered at this depth.
At 266 m (Figure 10(c), Table 6), increased dirt band
thickness reduces pillar strength from 15.83 MPa to
14.93 MPa, with the middle-positioned bands maintain-
ing the highest stability. Roof-positioned dirt bands, by
contrast, contribute to the lowest strength values, possibly
because of intensified stress near the roof at this depth. At
300 m (Figure 10(d), Table 7), the trend remains consis-
tent: pillar strength declines from 15.97 MPa at 0.2 m to
15.10 MPa at 0.5 m thickness, with middle-positioned
bands offering slightly better stability, while roof-based
bands show the lowest strength under the increasing stress.
For depths of 400 m (Figure 10(e), Table 8) and 500 m
(Figure 10(f), Table 9), the influence of dirt band thick-
ness on pillar strength is more pronounced. At 400 m, the
values decrease from 16.60 MPa to 15.67 MPa as thick-
ness increases from 0.2 m to 0.5 m. Pillars with middle
and floor-positioned bands maintain higher strength val-
ues than those with roof-positioned bands, where increased
stress levels near the roof amplify the adverse effect of
thicker dirt bands. At 500 m depth, thicker dirt bands
cause further weakening, with average strength reducing
from 16.97 MPa at 0.2 m thickness to 16.10 MPa at 0.5 m.
The slightly higher stability for middle-positioned bands
suggests some mitigation of stress concentration.
Overall, these results underscore the importance of
considering both thickness and placement of dirt bands
Table 4. Effect of dirt band thickness and location on pillar
strength at 100 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of Dirt Bed
Roof-
Interface Middle
Floor-
Interface
0.2 12.7 13.2 13.8 13.23
0.3 12.4 13.2 13.8 13.13
0.4 12 13 13.6 12.87
0.5 11.8 12.8 13.4 12.67
Table 5. Effect of dirt band thickness and location on pillar
strength at 200 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of Dirt Bed
Roof-
interface Middle
Floor-
interface
0.2 14 15.2 14.8 14.67
0.3 13.6 14.9 14.7 14.40
0.4 13.3 14.8 14.6 14.23
0.5 12.9 14.5 14.3 13.90
Table 6. Effect of dirt band thickness and location on pillar
strength at 266 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of Dirt Bed
Roof-
Interface Middle
Floor-
Interface
0.2 15.3 16.2 16 15.83
0.3 14.8 15.9 15.7 15.47
0.4 14.4 15.6 15.4 15.13
0.5 14.2 15.4 15.2 14.93
Table 7. Effect of dirt band thickness and location on pillar
strength at 300 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location Of Dirt Bed
Roof-
Interface Middle
Floor-
Interface
0.2 15.6 16.2 16.1 15.97
0.3 15.2 16 15.9 15.70
0.4 14.8 15.8 15.8 15.47
0.5 14.3 15.5 15.5 15.10
Table 8. Pillar strength affected by dirt band of varying
thickness at 400 m depth of cover
Thickness
of Dirt
Band
(m)
Pillar Strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of Dirt Bed
Roof-
Interface Middle
Floor-
Interface
0.2 16.3 16.9 16.6 16.60
0.3 15.6 16.7 16.5 16.27
0.4 15.2 16.4 16.3 15.97
0.5 14.9 16.1 16 15.67
Table 9. Pillar strength affected by dirt band of varying
thickness at 500 m depth of cover
Thickness
of dirt
band
(m)
Pillar strength (MPa)
Avg. Pillar
Strength
(MPa)
Location of dirt bed
Roof-
interface Middle
Floor-
interface
0.2 16.6 17.3 17 16.97
0.3 16 17 16.8 16.60
0.4 15.6 16.8 16.6 16.33
0.5 15.4 16.6 16.3 16.10