2012-05-11_PERMIT FILE - C1981033 ‎(3)‎

• Permit No: C1981033
• IBM Index Class Name: Permit File
• Doc Date: 5/11/2012
• Section_Exhibit Name: Rule 2.05 Operation and Reclamation Plans
• Media Type: D
• Archive: No

•
•
2.05.6(6)
Shale overburden
H = 3h(100) /SS
H = 3(12)(100)/33
H = 109 feet
h - mining height (12 feet)
8S - percent free swell (338)
The new Bear No. 3 Mine plan limits mining activities to an
overburden thickness of 110 feet and greater. Therefore, it is
unlikely that chimney collapse will penetrate to the surface above
the mine workings.
Gray, Bruhn and Truka (1977) physically documented the height of
collapse chimney subsidence above the Pittsburgh Seam for 127
cases. Gray, et. al. reported chimney subsidence height without
respect to the actual mining height or the lithology. Six of the
127 cases breached the ground surface 110 feet above the Pittsburgh
Seam. Table 13 presents the relative cumulative frequency
distribution for their data. Gray's (1977) chimney data from the
Pittsburgh Seam indicates that a chimney has a minor, approximately
4.7 percent, potential to penetrate the 110 foot overburden limit
in the Bear No. 3 Mine.
Trough Subsidence Prediction
Panel retreat mining, pillar robbing, as planned for the Bear No.
3 Mine is anticipated to cause surface subsidence in magnitudes
similar to that predicted by both the RMG and GW models. Table 14,
shows the subsidence magnitudes predicted by these models as
compared to the Operator's subsidence monitoring data. Considering
the various factors that influence subsidence; overburden
composition, percent extraction, barrier pillar size and location
and panel orientation, the subsidence values predicted by the RMG
and GW models are considered good. The worst case subsidence
prediction by the models was 6.4 feet.
It is anticipated that the maximum values of subsidence and tensile
ground strain will occur near the panels that border the outcrop
barrier pillar in the northwest portion of the proposed new mine
plan.
Subsidence Monitoring The Operator has monitored 13 subsidence
monitoring stations above the Bear No. 3 Mine since 1985.
2.05 -60
Rev. 11 -30 -93