1987-12-01_PERMIT FILE - C1981017 ‎(284)‎

• Permit No: C1981017
• IBM Index Class Name: PERMIT FILE
• Doc Date: 12/1/1987
• Doc Name: Subsidence Study By Dr. Bruce Collins
• Section_Exhibit Name: Chapter IV Appendix IV-F-4
• Media Type: D
• Archive: No

Figure 26
•
Subsidence Calculations, Monitoring Point MC-5 and Longwall 202
MC-5 is over 1h North, mined 1970 or 1971, and 150 ft from edge of
2 North pillar area, mined 1979-80, No. 3 mine, and 383 feet from
tailgate-startline corner, longwall 202, No. 2 mine. Point subsided
significantly from installation in 1981 to 7/3/84, but has been
stable since. Longwall 202 was started late 1982. Angle calculated
to determine whether or not point might have been in original subsid-
ence zone of longwall 202.
Distance from 202 tailgate startline corner (x) : 383 ft.
Surface elevation, MC-5: 11,010 ft.
Coal elevation, 202 tailagate: 10,195 ft.
Surface elevation above 202 tailgate: 10,920 ft.
Depth to coal (H) : 725 ft.
x MC-5
r - -
y 0,
H no scale
M bed
longwall 202
2 North — 12 North
Slope angle (0) :
0 = tan-
1 Y
x
= tan-1 90
383
= 13.22°
Apparent angle of draw (8) :
9 = tan-1 x
Hcos29
= tan-1 383
725cos213.22
= tan-1 383
725 0.95
= tan-1(0.56)
= 29.14°
Given 8's elsewhere apparently all below 20° it would appear that subsidence
at MC-5 is due entirely to mining in 2 North, No. 3 mine, with possible
reactivation of 12 North subsidence zone.