mine consists of seven heading
mains, three headings with flanking
returns and a segregated belt road in
the middle heading. As the mine does
not exist, there is not a designated
primary escapeway.
There are two results for the
contaminant test for the primary
escapeway shown in Table 1,
depending on which set of intake
roadways is adopted as the primary
escapeway. The results show that,
with the 157 segregation stoppings in
place, the contaminant is directed
predominantly into the mains
development area with a
concentration of 76 ppm. The other
three panels (including LW) modelled
a contamination around 15 ppm. The
greatest benefit modelled with this
arrangement of segregation was the
contaminant concentration of 4 ppm
adjacent to the 76 ppm in the mains.
The 4 ppm result came from the
single intake airway to the left of the
middle heading belt road in Figure 1.
The reason for the relatively low
level of contamination can be seen in
the pressure gradient plot for Case 0
in Figure 2. The heading that
returned the result of 4 ppm is
referred to in Figure 2 as primary.
This heading for the most part sat at a
higher static pressure than the
surrounding roads, particularly the
belt road where the contaminant was
concentrated. This resulted in leakage
paths flowing away from this
primary heading. The instances
where the static pressure in this
roadway drops below the belt road is
due to the placement of segregated
belt underpasses that were put into
the model to allow for transport
movements (operational requirement)
and balancing of the intake airway
pressures. This balancing caused the
drop in static pressure to below
that of the belt road in some
instances. This could be mitigated in
practice via the installation of
machine doors at the segregated
underpasses.
The results in Table 1 also show
that by removing all segregation from
the model, all inbye areas of the mine
received similar contaminant
concentrations of around 30 ppm.
This includes all working faces
and escapeways.
Case 1
Case 1 is based on a longwall mine in
the Bowen Basin in Queensland,
Australia. The trunk conveyor of the
mine is segregated on both sides from
the surrounding intakes with
203 segregation stoppings. The
primary escapeway of the mine is the
main travel road.
The contaminant test in Table 1
shows some very interesting and
unexpected results. The highest
contaminant results with the
segregation stoppings in place were
31 ppm in the primary escapeway,
30 ppm in the mains development
panel and 25 ppm in one of the
gateroads. Without the segregation
stoppings in place, the most
significant result was the reduction of
contaminant in the primary
escapeway by 30% down to 22 ppm.
The longwall result increased from
7 ppm to 17 ppm without the
segregation stoppings in place, while
the mains development and one of
the gateroads both had reductions in
the level of contaminant. As expected,
the contaminant was more spread out
and diluted without the segregation
stoppings and more concentrated in
particular areas.
The pressure gradient plot for
Case 1 in Figure 3 shows the belt
road at a higher pressure than the
primary escapeway most of the time.
The first 1000 m the primary
escapeway and the belt are in
separate drifts so the leakage would
be almost non-existent. The time
where the primary escapeway sits
above the belt road in static pressure
around the 2000 m mark is due to a
September 2014
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World Coal
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49
Figure 2.
Case 0: pressure plot.
Figure 3.
Case 1: pressure plot.
