2
Deep mining operations further highlight these chal-
lenges, as noted by [15], where weak roof conditions
require advanced roof support and strata control methods.
Researcher [16] discuss the critical role of monitoring sys-
tems in ensuring pillar stability in such complex environ-
ments, while [17] emphasizes the risk of dynamic failures
like coal bursts under high-stress conditions. Research by
[18] has introduced new design formulas accounting for
interface friction, which significantly affects pillar strength
but is often excluded from traditional models.
The integration of empirical and numerical methods is
essential to improve pillar strength prediction, as shown by
[4, 19], who applied regression techniques and probabilistic
methods to enhance prediction accuracy in Indian mines.
Recent advancements by [20] highlight the role of geologi-
cal discontinuities in influencing coal mass stability, show-
ing that joint density impacts failure modes and energy
release, especially in deep-seated coal mining operations.
Probabilistic approaches like those used by [21, 22]
bring greater reliability to stability assessments by address-
ing input variability in factors such as coal strength and
in-situ stress. Numerical modeling has further allowed
researchers to simulate depth-dependent stress distribu-
tions and predict the influence of roof-floor interactions
on pillar strength, as shown in studies by [23, 24]. [10]
also suggests that newer failure criteria, such as S-shaped
models, can account for confining stress effects at depth,
enhancing pillar design accuracy.
Furthermore, the influence of pillar width-to-height
(w/h) ratio on post-failure stability has been widely studied,
with findings from studies like [25] showing that narrower
pillars with high w/h ratios experience rapid failure under
high-stress conditions. Additional work by [26, 27] sup-
ports the idea that non-standard dimensions can improve
safety factors in specific geo-mining conditions. Studies
by [28, 29] provide insights on maintaining pillar stability
under varied depths and loading conditions, emphasizing a
probabilistic design that incorporates field data validation.
This study builds on these advancements by conduct-
ing numerical simulations to assess the impact of dirt bands
on coal pillar strength at varying depths. It aims to refine
traditional models, incorporating correction factors for dis-
continuities, thereby contributing to safer and more effec-
tive pillar design.
FIELD INVESTIGATION
The field investigation was conducted at Seam No. 1 in
Block-C of the Godavarikhani No. 11 Incline Mine, oper-
ated by Singareni Collieries Company Limited (SCCL).
The selected mine is located in the north-central part of
the Ramagundam coalfield, bounded by North latitudes
18°41'30" to 18°44'10" and East longitudes 79°32'58" to
79°34'54". The surface above the proposed Continuous
Miner (CM) Panel No. C‑2 is mostly free from important
surface features, with an abandoned road running across
the length of the panel and a few hutments near the south-
west boundary.
Seam No. 1, chosen for this study, has an average thick-
ness of 6.1 m and dips at an angle of 7° to 8° towards N60°E.
The seam contains various dirt bands, including shale, dull
coal, clay, and carbonaceous clay, totalling approximately
1.8 m in thickness and distributed consistently across the
seam (Figure 1). This area’s geological structure includes
two significant faults that create a horst formation. The
southern boundary of the coal block is defined by a fault
with a varying throw of 70 to 100 m, while an oblique fault
with a down throw ranging from 150 to 280 m bounds the
northern side. The coal-bearing formations in this region
belong to the Barakar formation, characterized by white to
greyish, coarse to medium-grained feldspathic sandstone.
The gradient of Seam No. 1 ranges between 1 in 6 and 1 in
11.
The mine has a history of successful depillaring opera-
tions using Continuous Miner (CM) technology in other
sections, specifically in Blocks “A” and “B” of Seam No. 1.
In Block “C,” mechanized depillaring is currently in prog-
ress in Panel No. C‑1, while the study is focused on the
adjacent Panel No. C‑2, located on the rise side of Panel
Coal
Shaly Coal
Coal/Shale thin bands
Clay/Carb.
l
Dull coal
LEGEND
Figure 1. Section of Seam No. 1 of panel No. C‑2
Top
secti
on2.5m
,
Middle
section,
2.5m
Floor coal,
1.1
m
Deep mining operations further highlight these chal-
lenges, as noted by [15], where weak roof conditions
require advanced roof support and strata control methods.
Researcher [16] discuss the critical role of monitoring sys-
tems in ensuring pillar stability in such complex environ-
ments, while [17] emphasizes the risk of dynamic failures
like coal bursts under high-stress conditions. Research by
[18] has introduced new design formulas accounting for
interface friction, which significantly affects pillar strength
but is often excluded from traditional models.
The integration of empirical and numerical methods is
essential to improve pillar strength prediction, as shown by
[4, 19], who applied regression techniques and probabilistic
methods to enhance prediction accuracy in Indian mines.
Recent advancements by [20] highlight the role of geologi-
cal discontinuities in influencing coal mass stability, show-
ing that joint density impacts failure modes and energy
release, especially in deep-seated coal mining operations.
Probabilistic approaches like those used by [21, 22]
bring greater reliability to stability assessments by address-
ing input variability in factors such as coal strength and
in-situ stress. Numerical modeling has further allowed
researchers to simulate depth-dependent stress distribu-
tions and predict the influence of roof-floor interactions
on pillar strength, as shown in studies by [23, 24]. [10]
also suggests that newer failure criteria, such as S-shaped
models, can account for confining stress effects at depth,
enhancing pillar design accuracy.
Furthermore, the influence of pillar width-to-height
(w/h) ratio on post-failure stability has been widely studied,
with findings from studies like [25] showing that narrower
pillars with high w/h ratios experience rapid failure under
high-stress conditions. Additional work by [26, 27] sup-
ports the idea that non-standard dimensions can improve
safety factors in specific geo-mining conditions. Studies
by [28, 29] provide insights on maintaining pillar stability
under varied depths and loading conditions, emphasizing a
probabilistic design that incorporates field data validation.
This study builds on these advancements by conduct-
ing numerical simulations to assess the impact of dirt bands
on coal pillar strength at varying depths. It aims to refine
traditional models, incorporating correction factors for dis-
continuities, thereby contributing to safer and more effec-
tive pillar design.
FIELD INVESTIGATION
The field investigation was conducted at Seam No. 1 in
Block-C of the Godavarikhani No. 11 Incline Mine, oper-
ated by Singareni Collieries Company Limited (SCCL).
The selected mine is located in the north-central part of
the Ramagundam coalfield, bounded by North latitudes
18°41'30" to 18°44'10" and East longitudes 79°32'58" to
79°34'54". The surface above the proposed Continuous
Miner (CM) Panel No. C‑2 is mostly free from important
surface features, with an abandoned road running across
the length of the panel and a few hutments near the south-
west boundary.
Seam No. 1, chosen for this study, has an average thick-
ness of 6.1 m and dips at an angle of 7° to 8° towards N60°E.
The seam contains various dirt bands, including shale, dull
coal, clay, and carbonaceous clay, totalling approximately
1.8 m in thickness and distributed consistently across the
seam (Figure 1). This area’s geological structure includes
two significant faults that create a horst formation. The
southern boundary of the coal block is defined by a fault
with a varying throw of 70 to 100 m, while an oblique fault
with a down throw ranging from 150 to 280 m bounds the
northern side. The coal-bearing formations in this region
belong to the Barakar formation, characterized by white to
greyish, coarse to medium-grained feldspathic sandstone.
The gradient of Seam No. 1 ranges between 1 in 6 and 1 in
11.
The mine has a history of successful depillaring opera-
tions using Continuous Miner (CM) technology in other
sections, specifically in Blocks “A” and “B” of Seam No. 1.
In Block “C,” mechanized depillaring is currently in prog-
ress in Panel No. C‑1, while the study is focused on the
adjacent Panel No. C‑2, located on the rise side of Panel
Coal
Shaly Coal
Coal/Shale thin bands
Clay/Carb.
l
Dull coal
LEGEND
Figure 1. Section of Seam No. 1 of panel No. C‑2
Top
secti
on2.5m
,
Middle
section,
2.5m
Floor coal,
1.1
m