1
25-034
Evaluation of Alternative Chain Pillar Designs in a Deep
Longwall Mine
Zoheir Khademian
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Daniel Su
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Mark Van Dyke
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Steve Hicks
Coronado Global Resources, Inc., Beckley, WV
Mark Mazzella
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Nicole Evanek
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Yuting Xue
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Todd Minoski
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
ABSTRACT
Design of chain pillars in a longwall mine setting is one
of the main engineering controls on the global and local
stability of the mine. Challenges with roof instabilities,
floor heaves, and pillar failures can be alleviated, to some
extent, by careful design of gateroad configurations and
chain pillars. This work investigates three different alterna-
tive designs in a three-entry-system gateroad configuration
with an inter-panel barrier in a longwall mine in Virginia.
Starting with the current design, which has faced challenges
such as excessive floor heave, a geomechanical model devel-
oped in 3DEC software is validated by monitoring in-situ
pillar stress in the yield, abutment, and barrier pillars in the
mine. Next, three different chain pillar designs are evaluated
in the model with a focus on roof sagging, floor heave, and
pillar average stress. Results show the relationships among
the alternative designs and instabilities associated with roof,
pillar, and floor in the study mine, providing insights for
optimizing longwall mining designs in deep-cover settings.
INTRODUCTION
Deep longwall mining under mountainous terrain intro-
duces unique ground control challenges that might not be
present in shallower operations. These challenges include
induced seismicity in the pillar, roof or floor, gateroad
closure due to roof sag or floor heave, and rib instabilities.
Pillar sizing and mine layout design are known engineering
factors that can potentially mitigate geology-driven insta-
bilities. However, geology variation along and across long-
wall panels make it difficult to come up with a single design
for a district or entire mine. In other words, a mine layout
design needs to accommodate a range of possible geology
variations in the intended area. For example, floor geol-
ogy might change along a panel, so one layout that works
for the area with a strong sandy shale floor might lead to
operationally problematic floor heave where floor is weak
fireclay. Thus, alternative mine designs need to be evaluated
for a range of mine geology with respect to potential chal-
lenges such as roof sag, floor heave, and induced seismicity.
However, the question is what tools and methodologies are
necessary for finding an optimum design that minimizes
geology-controlled ground instability. The current practice
in the mining industry is to follow previous experiences,
but in the case that a new design is being tested with little
to no historic data and experience, new tools are needed for
evaluation purposes.
NIOSH has initiated a research project in a deep
longwall mine in Virginia where a new mine area is being
developed with a 1,000-ft, single-panel district design and
220-ft barrier pillars isolating each panel. The previous
25-034
Evaluation of Alternative Chain Pillar Designs in a Deep
Longwall Mine
Zoheir Khademian
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Daniel Su
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Mark Van Dyke
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Steve Hicks
Coronado Global Resources, Inc., Beckley, WV
Mark Mazzella
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Nicole Evanek
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Yuting Xue
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
Todd Minoski
CDC NIOSH, Pittsburgh Mining Research Division,
Pittsburgh, PA
ABSTRACT
Design of chain pillars in a longwall mine setting is one
of the main engineering controls on the global and local
stability of the mine. Challenges with roof instabilities,
floor heaves, and pillar failures can be alleviated, to some
extent, by careful design of gateroad configurations and
chain pillars. This work investigates three different alterna-
tive designs in a three-entry-system gateroad configuration
with an inter-panel barrier in a longwall mine in Virginia.
Starting with the current design, which has faced challenges
such as excessive floor heave, a geomechanical model devel-
oped in 3DEC software is validated by monitoring in-situ
pillar stress in the yield, abutment, and barrier pillars in the
mine. Next, three different chain pillar designs are evaluated
in the model with a focus on roof sagging, floor heave, and
pillar average stress. Results show the relationships among
the alternative designs and instabilities associated with roof,
pillar, and floor in the study mine, providing insights for
optimizing longwall mining designs in deep-cover settings.
INTRODUCTION
Deep longwall mining under mountainous terrain intro-
duces unique ground control challenges that might not be
present in shallower operations. These challenges include
induced seismicity in the pillar, roof or floor, gateroad
closure due to roof sag or floor heave, and rib instabilities.
Pillar sizing and mine layout design are known engineering
factors that can potentially mitigate geology-driven insta-
bilities. However, geology variation along and across long-
wall panels make it difficult to come up with a single design
for a district or entire mine. In other words, a mine layout
design needs to accommodate a range of possible geology
variations in the intended area. For example, floor geol-
ogy might change along a panel, so one layout that works
for the area with a strong sandy shale floor might lead to
operationally problematic floor heave where floor is weak
fireclay. Thus, alternative mine designs need to be evaluated
for a range of mine geology with respect to potential chal-
lenges such as roof sag, floor heave, and induced seismicity.
However, the question is what tools and methodologies are
necessary for finding an optimum design that minimizes
geology-controlled ground instability. The current practice
in the mining industry is to follow previous experiences,
but in the case that a new design is being tested with little
to no historic data and experience, new tools are needed for
evaluation purposes.
NIOSH has initiated a research project in a deep
longwall mine in Virginia where a new mine area is being
developed with a 1,000-ft, single-panel district design and
220-ft barrier pillars isolating each panel. The previous