Page 193 - Advances In Productive, Safe, and Responsible Coal Mining

172 Advances in Productive, Safe, and Responsible Coal Mining

Assuming the entire coal seam thickness is extracted, mining height is the sum of OSD
thickness extracted (from roof and floor) and seam thickness, that is,

Mining height ¼ OSD thickness + seam thickness (9.3)

Substituting Eq. (9.2) in Eq. (9.3) gives.

Mining height ¼ 0:1669 seam thickness + 5:4945 (9.4)
Thus, change in mining height as a function of change in seam height can be repre-
sented as.

ð
∂ Mining heightÞ
¼ 0:1669 (9.5)
∂ Seam thicknessÞ
ð
Accordingly, for every 1.0in. (2.5cm) reduction in seam height, mining height
decreases by only 0.2in. (0.4cm). Comparing phase 1 and phase 2 data, coal seam
height decreased by 1.9in. (4.9cm), which should have resulted in mining height
decreasing by only 0.3in. (0.8cm); however, mining height actually decreased by
almost 1.0in. (2.5cm) as shown in Table 9.5. When only the period immediately after
the EAP is considered (pillar 1), instead of the reduced seam height resulting in a
mining height reduction of 0.3in., the actual reduction was almost 1.7in. These
greater-than-expected decreases in mining height are attributed to the effectiveness
of education and awareness in controlling OSD.
As previously mentioned, immediately following the EAP, mining height was
reduced by 1.5in. (3.8cm); however, by the end of phase 2 data collection efforts,
mining height had returned to and even exceeded pre-EAP levels. This emphasizes
the need for ongoing monitoring and refresher EAPs. The research team rec-
ommended a quarterly refresher EAP that could easily be incorporated with routine
safety shares owing to the fact that mining OSD generates higher levels of silica dust
exposure [17].

Table 9.5 Summary of dilution measurements (1.0ft50.3m)
Floor (ft) Roof (ft) Coal seam (ft) Mining height (ft)

Pre-EAP average 0.80 0.09 5.64 6.49
Post-EAP average 0.87 0.06 5.48 6.41
Pillar 1 0.78 0.08 5.48 6.35
Pillar 2 0.80 0.07 5.51 6.37
Pillar 3 0.95 0.04 5.51 6.46
Pillar 4 1.00 0.07 5.40 6.47