PERMFILE40335

• Permit No: C1981022
• IBM Index Class Name: Permit File
• Doc Date: 1/27/2003
• Doc Name: Predicted D Seam Longwall Subsidence Report 2/26/03
• Section_Exhibit Name: Exhibit 2.05-E8 Part 6
• Media Type: D
• Archive: No

Elk Creek Mine Subsidence Page 26 February 26, 2003
been previously subsided. The only constant for all Elk Creek
Mine panels is the 825-ft (251 m) longwall panel width. Entering
Figure 9 (Graph C1) with the 251 m depth on the y-axis and
progressing to the local overburden depth on the x-axis provides
the width/depth multiplier for the mining height. If the
overburden has not been previously subsided, i.e. is virgin
ground, an additional 0.9 multiplier is applied to the
width/depth factored mining height. The NCB (1975) `Subsidence
Engineers' Handbook" states:
`When considering workings with any w/h value in a
virgin area the prediction from Fig. 3 (which was
• I
I
derived from cases of multi-seam workings) should be
reduced by a multiplying factor of 0.9."
._,----
The predicted maximum vertical subsidence-(",max) of the
ground surface above each-selected individual panel ribside
locations was calculated by multiplying the local longwall mining
height by the panel width/depth correction factor and, if
appropriate, by the 0.9 virgin ground correction. The panel
width/depth correction factor graph is included as Figure 8
(Graph C1 in Appendix C). The "Limit of Subsidence" line on
Figure 8 is defined by the conservative 35° angle of draw from I
the panel ribside to the ground-surface. This is the zero (0)
subsidence contour on the individual panel subsidence contour
plots, Plate 3 for Panel Group 1, Plate 8 for Panel Group 2 and •I
Plate 13 for Panel Group 3. The "Limit of Subsidence" equal to
the tangent of 35° times the local overburden depth: ~
(0.70(local overburden depth)).
The distance to the selected subsidence contour values I
(1-f t, 2-f t, 4-ft, 6-ft, 8-ft and 10-ft) were then extracted from
Figure 8 for the local panel width/depth ratio on the y-axis
(also Graph C3, Appendx,G)-===;Mwngparallel to the__x-axis to I
the proportion of the maximum subsidence (5,,,;x)--represen'
contour subsidence value. The difference between the distance
from the panel ribside to the center of the panel in terms of
depth (divided by the depth) projected down to the x-axis of
Figure 8 and the distance from the proportion of S,,,,x for the
contour subsidence value projected down to x-axis value is the (-
distance between the ribside and contour subsidence at the
selected location divided by the local overburden depth. The
predicted single panel vertical subsidence at the selected I
locations was assumed not to be affected by the mining of
adjacent panels, i.e. not affected by the possible crushing of
adjacent gateroad pillars. I
The following example for locating the 6-foot subsidence
contour at the selected Panel #3 location N-3,675V (3,675-ft from •I
-26-