2
and pinpoint necessary adjustments to the mine ventilation
system in the unlikely event of a gas well breach.
In this study, NIOSH researchers utilize a ventilation
network model and a scaled physical model to simulate a
variety of hypothetical gas breach scenarios in a longwall
mine, with the objective of addressing three key questions
crucial to mine safety and ventilation efficiency: 1) inves-
tigate the dynamics of gas migration within the model if
a gas breach were to occur 2) explore whether there is a
quantifiable correlation between gas inflow rates and gas
concentration levels at critical locations 3) simulate the
maximum gas inflow rate that the mine’s ventilation system
can safely handle.
SCALED PHYSICAL MODEL AND
NETWORK-BASED VENTSIM MODEL
In this study, both a ventilation network model and a scaled
physical model are employed to simulate worst-case scenar-
ios of unconventional gas well breaches in underground coal
mines. Since the study relies on hypothetical cases, with no
available field data or prior experience, modeling becomes
the primary approach. Each method has its own strengths
and limitations. The physical model allows for direct obser-
vation and measurement of airflow and gas concentrations,
but the modifications are cumbersome. Numerical model-
ing, on the other hand, can simulate complex, large-scale
ventilation systems that are challenging to replicate physi-
cally. By combining both approaches, the numerical models
provide flexibility and efficiency, while the physical models
offer validation and practical insight within its limits.
Longwall Instrumented Aerodynamic Model (LIAM)
LIAM is a 1:30 scaled physical model that is constructed
to simulate a single longwall panel (as shown in Figure 1).
The model design depicts a 3-entry Headgate and 3-entry
Tailgate that is typical for longwall section development.
The model is scaled for a 720-ft (219-m) face and a 400-
ft (122-m) gob area. LIAM can simulate inaccessible gob
areas as well as the performance of mine ventilation systems
that are easily controlled and monitored. Typical test sce-
narios incorporate ventilation controls and airflow quanti-
ties as supplied by mine cooperators and may be adjusted
quickly and easily for various test scenarios. Bleeder fans as
well as a main mine fan are utilized for test scenarios. Two
gob ventilation boreholes (GVB) are incorporated into the
LIAM design.
Sixty hot-wire anemometers are installed throughout
the physical model, including the mine entries, longwall
face, mined gob areas, GVBs, and bleeder fan location. The
data acquisition system records the airflow from the sen-
sors for the duration of each test. A smoke generator and
theatrical smoke are used to visually confirm airflow path-
ways, eddy currents, and gob-to-face interactions in order
to confirm that the test scenario parameters conform to the
specified ventilation design in place for the test.
Figure 1. LIAM physical model
and pinpoint necessary adjustments to the mine ventilation
system in the unlikely event of a gas well breach.
In this study, NIOSH researchers utilize a ventilation
network model and a scaled physical model to simulate a
variety of hypothetical gas breach scenarios in a longwall
mine, with the objective of addressing three key questions
crucial to mine safety and ventilation efficiency: 1) inves-
tigate the dynamics of gas migration within the model if
a gas breach were to occur 2) explore whether there is a
quantifiable correlation between gas inflow rates and gas
concentration levels at critical locations 3) simulate the
maximum gas inflow rate that the mine’s ventilation system
can safely handle.
SCALED PHYSICAL MODEL AND
NETWORK-BASED VENTSIM MODEL
In this study, both a ventilation network model and a scaled
physical model are employed to simulate worst-case scenar-
ios of unconventional gas well breaches in underground coal
mines. Since the study relies on hypothetical cases, with no
available field data or prior experience, modeling becomes
the primary approach. Each method has its own strengths
and limitations. The physical model allows for direct obser-
vation and measurement of airflow and gas concentrations,
but the modifications are cumbersome. Numerical model-
ing, on the other hand, can simulate complex, large-scale
ventilation systems that are challenging to replicate physi-
cally. By combining both approaches, the numerical models
provide flexibility and efficiency, while the physical models
offer validation and practical insight within its limits.
Longwall Instrumented Aerodynamic Model (LIAM)
LIAM is a 1:30 scaled physical model that is constructed
to simulate a single longwall panel (as shown in Figure 1).
The model design depicts a 3-entry Headgate and 3-entry
Tailgate that is typical for longwall section development.
The model is scaled for a 720-ft (219-m) face and a 400-
ft (122-m) gob area. LIAM can simulate inaccessible gob
areas as well as the performance of mine ventilation systems
that are easily controlled and monitored. Typical test sce-
narios incorporate ventilation controls and airflow quanti-
ties as supplied by mine cooperators and may be adjusted
quickly and easily for various test scenarios. Bleeder fans as
well as a main mine fan are utilized for test scenarios. Two
gob ventilation boreholes (GVB) are incorporated into the
LIAM design.
Sixty hot-wire anemometers are installed throughout
the physical model, including the mine entries, longwall
face, mined gob areas, GVBs, and bleeder fan location. The
data acquisition system records the airflow from the sen-
sors for the duration of each test. A smoke generator and
theatrical smoke are used to visually confirm airflow path-
ways, eddy currents, and gob-to-face interactions in order
to confirm that the test scenario parameters conform to the
specified ventilation design in place for the test.
Figure 1. LIAM physical model