2
that may infiltrate an underground coal mine during a
potential shale gas well breach [3–6].
Managing mine ventilation systems for longwall opera-
tions is a complex and time-consuming daily process for
mine engineers and ventilation managers. Understanding
the possible impacts to the mine ventilation system is
paramount to mine management in order to provide an
adequate ventilation design and planned response options.
Given the predicted quantities of methane that may infil-
trate into an underground coal mine during a shale gas well
breach, physical modeling provides critical information
by simulating mine ventilation performance through con-
trolled conditions. A possible unplanned shale gas inflow
from a hypothetical breached gas well casing presents a
scenario potentially detrimental to a mine ventilation sys-
tem, mine production, and miners’ safety. The results from
the Longwall Instrumented Aerodynamic Model (LIAM)
experiments and tracer gas studies provide ventilation engi-
neers the necessary information for adequate ventilation
design planning and the basis for developing event response
protocols for breach gas mitigation plans and required
agency approvals.
The LIAM (Figure 1) was designed and constructed
as a 1:30 scale physical model to simulate a portion of a
longwall operation. The LIAM design is a three-entry head-
gate and tailgate longwall panel design commonly utilized
in Pittsburgh Coal Seam longwall operations [1]. Hotwire
anemometers provide velocity readings in the LIAM entries
and mined gob areas. The differential pressure across the
face is recorded and two thermocouples record air tempera-
ture. Depending upon the design test scenario, the LIAM
utilizes a main mine fan and/or a bleeder fan. Mine fans
and entry regulators are adjusted to ventilation specifica-
tions for each test scenario. Theatrical smoke is used for
visualization of airflow paths on the longwall face and
behind the shields, eddy currents, and gob-face interactions
in order to validate that airflow pathways correspond to the
design test scenario. Sulfur hexafluoride (SF6) is utilized as
a surrogate for methane for the tracer-gas-based analysis of
the breached gas [7, 8].
METHODOLOGY
Scenarios for LIAM experimental testing are designed to
utilize cooperating mine ventilation data and NIOSH
researchers’ assumptions for inflow values generated from
Discrete Fracture Network (DFN) and Computational
Fluid Dynamics (CFD) models. These models predicted
the potential inflow quantities and locations. The mine
ventilation plan used is typical of longwall mines in the
Pittsburgh Coal Seam. The LIAM is configured with airflow
quantities and ventilation controls commonly approved
by the Mine Safety and Health Administration (MSHA).
Shown in Figure 2, the LIAM is geometrically designed to
represent a single longwall panel with a three-entry head-
gate and a three-entry tailgate configuration with two-
bleeder entries with exhausting ventilation [9]. Other mine
ventilation configurations can be simulated on the LIAM.
Concentrations of SF6 are determined by gas chromatogra-
phy (GC) using NIOSH method 6602 [10]. The method
uses Ultra P5 as a carrier gas (95% methane, 5% argon) and
produces a limit of measurement of 1.0 ppb in air.
In this paper, four test scenarios are presented. Each
scenario is represented by a test series. Table 1 lists the
inflow rates and insertion points for each test series. Test
Series A has an inflow value of 340 cfm inserted into the
LIAM at the mine roof at 30 location points (8 insertion
points located in the tailgate corner gob behind the tailgate
shields and 22 insertion points located inby the tailgate pil-
lar extending towards the tailgate bleeder evaluation point,
BEP). Test Series B has an inflow value of 400 cfm inserted
at the mine roof at 30 location points (14 insertion points
located in the tailgate corner gob behind the tailgate shields
and 16 insertion points that were located inby the tailgate
pillar extending towards the tailgate BEP). Test Series B
is also based upon work conducted by Ajayi et al.[11] in
which most of the predicted inflow values ranged from 1 to
400 cfm. Consequently, the highest predicted inflow value,
400 cfm, was chosen for this series of tests. Test Series C
has an inflow value of 400 cfm inserted at the mine roof
at 30 location points (6 insertion points located in the tail-
gate corner gob behind the tailgate shields and 24 insertion
points located inby the tailgate pillar) and was predicted by
Figure 1. The LIAM is shown in the NIOSH PMRD
laboratory
that may infiltrate an underground coal mine during a
potential shale gas well breach [3–6].
Managing mine ventilation systems for longwall opera-
tions is a complex and time-consuming daily process for
mine engineers and ventilation managers. Understanding
the possible impacts to the mine ventilation system is
paramount to mine management in order to provide an
adequate ventilation design and planned response options.
Given the predicted quantities of methane that may infil-
trate into an underground coal mine during a shale gas well
breach, physical modeling provides critical information
by simulating mine ventilation performance through con-
trolled conditions. A possible unplanned shale gas inflow
from a hypothetical breached gas well casing presents a
scenario potentially detrimental to a mine ventilation sys-
tem, mine production, and miners’ safety. The results from
the Longwall Instrumented Aerodynamic Model (LIAM)
experiments and tracer gas studies provide ventilation engi-
neers the necessary information for adequate ventilation
design planning and the basis for developing event response
protocols for breach gas mitigation plans and required
agency approvals.
The LIAM (Figure 1) was designed and constructed
as a 1:30 scale physical model to simulate a portion of a
longwall operation. The LIAM design is a three-entry head-
gate and tailgate longwall panel design commonly utilized
in Pittsburgh Coal Seam longwall operations [1]. Hotwire
anemometers provide velocity readings in the LIAM entries
and mined gob areas. The differential pressure across the
face is recorded and two thermocouples record air tempera-
ture. Depending upon the design test scenario, the LIAM
utilizes a main mine fan and/or a bleeder fan. Mine fans
and entry regulators are adjusted to ventilation specifica-
tions for each test scenario. Theatrical smoke is used for
visualization of airflow paths on the longwall face and
behind the shields, eddy currents, and gob-face interactions
in order to validate that airflow pathways correspond to the
design test scenario. Sulfur hexafluoride (SF6) is utilized as
a surrogate for methane for the tracer-gas-based analysis of
the breached gas [7, 8].
METHODOLOGY
Scenarios for LIAM experimental testing are designed to
utilize cooperating mine ventilation data and NIOSH
researchers’ assumptions for inflow values generated from
Discrete Fracture Network (DFN) and Computational
Fluid Dynamics (CFD) models. These models predicted
the potential inflow quantities and locations. The mine
ventilation plan used is typical of longwall mines in the
Pittsburgh Coal Seam. The LIAM is configured with airflow
quantities and ventilation controls commonly approved
by the Mine Safety and Health Administration (MSHA).
Shown in Figure 2, the LIAM is geometrically designed to
represent a single longwall panel with a three-entry head-
gate and a three-entry tailgate configuration with two-
bleeder entries with exhausting ventilation [9]. Other mine
ventilation configurations can be simulated on the LIAM.
Concentrations of SF6 are determined by gas chromatogra-
phy (GC) using NIOSH method 6602 [10]. The method
uses Ultra P5 as a carrier gas (95% methane, 5% argon) and
produces a limit of measurement of 1.0 ppb in air.
In this paper, four test scenarios are presented. Each
scenario is represented by a test series. Table 1 lists the
inflow rates and insertion points for each test series. Test
Series A has an inflow value of 340 cfm inserted into the
LIAM at the mine roof at 30 location points (8 insertion
points located in the tailgate corner gob behind the tailgate
shields and 22 insertion points located inby the tailgate pil-
lar extending towards the tailgate bleeder evaluation point,
BEP). Test Series B has an inflow value of 400 cfm inserted
at the mine roof at 30 location points (14 insertion points
located in the tailgate corner gob behind the tailgate shields
and 16 insertion points that were located inby the tailgate
pillar extending towards the tailgate BEP). Test Series B
is also based upon work conducted by Ajayi et al.[11] in
which most of the predicted inflow values ranged from 1 to
400 cfm. Consequently, the highest predicted inflow value,
400 cfm, was chosen for this series of tests. Test Series C
has an inflow value of 400 cfm inserted at the mine roof
at 30 location points (6 insertion points located in the tail-
gate corner gob behind the tailgate shields and 24 insertion
points located inby the tailgate pillar) and was predicted by
Figure 1. The LIAM is shown in the NIOSH PMRD
laboratory