12
Transition
phase
Enhanced
reduction
phase
Figure 11. Variation in average %strength reduction of varying thickness of dirt bands at
various positions at various depths of cover
Table 10. Results of Numerical simulation based on depth-dependent strength variations of the modelled coal pillar impacted
with dirt bands on varying thickness
Depth of
cover
(m)
Pillar strength
without dirt bands
(Mpa)
Impact of dirt bands
Avg. %
reduction
Thickness
(m)
Avg. Pillar
strength
(MPa)
Reduction in Pillar
strength
(MPa) %Reduction
100 13.8 0.2 13.23 0.57 4.11 5.98
0.3 13.13 0.67 4.83
0.4 12.87 0.93 6.76
0.5 12.67 1.13 8.21
200 15.2 0.2 14.67 0.53 3.51 5.92
0.3 14.40 0.80 5.26
0.4 14.23 0.97 6.36
0.5 13.90 1.30 8.55
266 16.6 0.2 15.83 0.77 4.62 7.58
0.3 15.47 1.13 6.83
0.4 15.13 1.47 8.84
0.5 14.93 1.67 10.04
300 17 0.2 15.97 1.03 6.08 8.48
0.3 15.70 1.30 7.65
0.4 15.47 1.53 9.02
0.5 15.10 1.90 11.18
400 17.6 0.2 16.60 1.00 5.68 8.38
0.3 16.27 1.33 7.58
0.4 15.97 1.63 9.28
0.5 15.67 1.93 10.98
500 18 0.2 16.97 1.03 5.74 8.33
0.3 16.60 1.40 7.78
0.4 16.33 1.67 9.26
0.5 16.10 1.90 10.56
Transition
phase
Enhanced
reduction
phase
Figure 11. Variation in average %strength reduction of varying thickness of dirt bands at
various positions at various depths of cover
Table 10. Results of Numerical simulation based on depth-dependent strength variations of the modelled coal pillar impacted
with dirt bands on varying thickness
Depth of
cover
(m)
Pillar strength
without dirt bands
(Mpa)
Impact of dirt bands
Avg. %
reduction
Thickness
(m)
Avg. Pillar
strength
(MPa)
Reduction in Pillar
strength
(MPa) %Reduction
100 13.8 0.2 13.23 0.57 4.11 5.98
0.3 13.13 0.67 4.83
0.4 12.87 0.93 6.76
0.5 12.67 1.13 8.21
200 15.2 0.2 14.67 0.53 3.51 5.92
0.3 14.40 0.80 5.26
0.4 14.23 0.97 6.36
0.5 13.90 1.30 8.55
266 16.6 0.2 15.83 0.77 4.62 7.58
0.3 15.47 1.13 6.83
0.4 15.13 1.47 8.84
0.5 14.93 1.67 10.04
300 17 0.2 15.97 1.03 6.08 8.48
0.3 15.70 1.30 7.65
0.4 15.47 1.53 9.02
0.5 15.10 1.90 11.18
400 17.6 0.2 16.60 1.00 5.68 8.38
0.3 16.27 1.33 7.58
0.4 15.97 1.63 9.28
0.5 15.67 1.93 10.98
500 18 0.2 16.97 1.03 5.74 8.33
0.3 16.60 1.40 7.78
0.4 16.33 1.67 9.26
0.5 16.10 1.90 10.56