7
pressure on pillar stability, as deeper cover leads to increased
confinement and higher stress at failure.
Table 3 provides a quantitative comparison between
the pillar strength values obtained from the numerical
simulation and those calculated using Sheorey’s empirical
approach. For depths up to 300 m, there is good agreement
between the two methods, as indicated by relatively low
As depth increases, the contours of vertical stress inten-
sify in the central section of the pillar, indicating greater
stress concentration due to the added overburden load. The
accompanying stress-strain curves reveal that higher depths
result in higher peak stress values, showing the relationship
between increasing depth and pillar load-bearing capac-
ity. This pattern emphasizes the influence of overburden
Table 2 Properties used for modelling of coal pillar
Strata
Young’s
Modulus
(E)
MPa
Poisson’s
Ratio
(ν)
Bulk
Modulus
(K)
GPa
Shear
Modulus
(G)
GPa
Density of
Rock Mass
(d)
Kg/m3
UCS of
Intact Rock
(σ
c )
MPa
Tensile
Strength
(σ
t )
MPa
Rock Mass
Rating
(RMR)
Coal 2 0.25 1.33 0.80 1400 30.5 3.05 48
Shale 7.68 0.14 3.56 3.37 2292 47 4.7 47
Sandstone 7 0.25 4.67 2.80 2250 30 3 48
Discontinuities 0.5 0.25 0.33 0.20 1000 5 0.5 20
(a) (b) (c)
(d) (e) (f)
Figure 7. Strength of coal pillar based on stress-strain behaviour at different depths of cover, (a) 100 m (b) 200 m (c) 266 m
(d) 300 m (e) 400 m (f) 500 m
pressure on pillar stability, as deeper cover leads to increased
confinement and higher stress at failure.
Table 3 provides a quantitative comparison between
the pillar strength values obtained from the numerical
simulation and those calculated using Sheorey’s empirical
approach. For depths up to 300 m, there is good agreement
between the two methods, as indicated by relatively low
As depth increases, the contours of vertical stress inten-
sify in the central section of the pillar, indicating greater
stress concentration due to the added overburden load. The
accompanying stress-strain curves reveal that higher depths
result in higher peak stress values, showing the relationship
between increasing depth and pillar load-bearing capac-
ity. This pattern emphasizes the influence of overburden
Table 2 Properties used for modelling of coal pillar
Strata
Young’s
Modulus
(E)
MPa
Poisson’s
Ratio
(ν)
Bulk
Modulus
(K)
GPa
Shear
Modulus
(G)
GPa
Density of
Rock Mass
(d)
Kg/m3
UCS of
Intact Rock
(σ
c )
MPa
Tensile
Strength
(σ
t )
MPa
Rock Mass
Rating
(RMR)
Coal 2 0.25 1.33 0.80 1400 30.5 3.05 48
Shale 7.68 0.14 3.56 3.37 2292 47 4.7 47
Sandstone 7 0.25 4.67 2.80 2250 30 3 48
Discontinuities 0.5 0.25 0.33 0.20 1000 5 0.5 20
(a) (b) (c)
(d) (e) (f)
Figure 7. Strength of coal pillar based on stress-strain behaviour at different depths of cover, (a) 100 m (b) 200 m (c) 266 m
(d) 300 m (e) 400 m (f) 500 m