3
Three hypothetical gas breach scenarios were tested
using the LIAM model, with inflows of 340 cfm, 500 cfm,
and 1,300 cfm. Each scenario included 30 gas insertion
locations: 8 positioned in the tailgate corner gob behind
the tailgate shields and 22 located inby the longwall tail-
gate towards the tailgate Bleeder Evaluation Point (BEP),
as illustrated in Figure 2. The gas insertion points in the
physical model were derived from assumptions made by
Discrete Fracture Network (DFN) and Computational
Fluid Dynamics (CFD) researchers as part of ongoing
NIOSH projects (Watkin et al., 2021 Ajayi et al., 2022).
These 30 insertions facilitate gas flow into the gob directly
behind the tailgate shields and along the tailgate pillar line.
The selected inflow locations reflect a combination of both
researchers’ assumptions, adapted to align with the LIAM
test scenarios.
Table 1 presents the airflows at key locations for each
test scenario. The ventilation design air quantities used in
the LIAM test scenarios were supplied by cooperators from
the Pittsburgh Seam longwall mine. These scenarios incor-
porated various airflow quantities from the longwall face,
bleeder entry, and tailgate entry. Each scenario included
the standard MSHA-approved (Mine Safety and Health
Administration) T-Split configuration on the tailgate side
of the longwall face, with airflow in the tailgate entries des-
ignated as an intake air course (MSHA,1996). Belt entry
air was not utilized to ventilate the longwall face.
Sulfur hexafluoride gas is used as the tracer gas, inserted
into LIAM at a concentration of 25 ppm. Samples are ana-
lyzed via Gas Chromatography (GC) using Ultra P5 as
a carrier gas (comprising 95% methane and 5% argon),
achieving a measurement sensitivity of 1.0 ppb in air. The
Figure 2. Tracer gas release locations and airflow monitoring locations in LIAM
Table 1. Airflows at some locations for each test scenario
Test Scenario
Gas Inflow
Rate CFM
Headgate
Shield #17
CFM
Tailgate
Shield #115
CFM
Tailgate
Entries (3)
Outby Face
CFM
Tailgate
Entry Outby
BEP CFM
Bleeder
Entries from
Headgate
CFM
Location indicator in Figure 2 in A B C D E
A 340 78996 42199 55004 50882 69303
B 500 80833 43546 55544 52318 69883
C 1300 83542 43929 55947 52520 69858
Three hypothetical gas breach scenarios were tested
using the LIAM model, with inflows of 340 cfm, 500 cfm,
and 1,300 cfm. Each scenario included 30 gas insertion
locations: 8 positioned in the tailgate corner gob behind
the tailgate shields and 22 located inby the longwall tail-
gate towards the tailgate Bleeder Evaluation Point (BEP),
as illustrated in Figure 2. The gas insertion points in the
physical model were derived from assumptions made by
Discrete Fracture Network (DFN) and Computational
Fluid Dynamics (CFD) researchers as part of ongoing
NIOSH projects (Watkin et al., 2021 Ajayi et al., 2022).
These 30 insertions facilitate gas flow into the gob directly
behind the tailgate shields and along the tailgate pillar line.
The selected inflow locations reflect a combination of both
researchers’ assumptions, adapted to align with the LIAM
test scenarios.
Table 1 presents the airflows at key locations for each
test scenario. The ventilation design air quantities used in
the LIAM test scenarios were supplied by cooperators from
the Pittsburgh Seam longwall mine. These scenarios incor-
porated various airflow quantities from the longwall face,
bleeder entry, and tailgate entry. Each scenario included
the standard MSHA-approved (Mine Safety and Health
Administration) T-Split configuration on the tailgate side
of the longwall face, with airflow in the tailgate entries des-
ignated as an intake air course (MSHA,1996). Belt entry
air was not utilized to ventilate the longwall face.
Sulfur hexafluoride gas is used as the tracer gas, inserted
into LIAM at a concentration of 25 ppm. Samples are ana-
lyzed via Gas Chromatography (GC) using Ultra P5 as
a carrier gas (comprising 95% methane and 5% argon),
achieving a measurement sensitivity of 1.0 ppb in air. The
Figure 2. Tracer gas release locations and airflow monitoring locations in LIAM
Table 1. Airflows at some locations for each test scenario
Test Scenario
Gas Inflow
Rate CFM
Headgate
Shield #17
CFM
Tailgate
Shield #115
CFM
Tailgate
Entries (3)
Outby Face
CFM
Tailgate
Entry Outby
BEP CFM
Bleeder
Entries from
Headgate
CFM
Location indicator in Figure 2 in A B C D E
A 340 78996 42199 55004 50882 69303
B 500 80833 43546 55544 52318 69883
C 1300 83542 43929 55947 52520 69858