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

19 - l
Therefore the second set of data were used, although
admittedly the points in the area of longwall panel 301
are much more widely spaced, to estimate the angle of draw
in a more stable area. Longwall face 301 was stopped in
early 1981. The closest data point, TP-4 , 340 feet ahead
of the tailgate corner of longwall 301, subsided 0.19 feet
between 1981 and 8/9/85 , and was nearly stable by August of
1985 , having moved -0. 06 feet since September of 1984 .
Points TP-2 , 820 feet NW of the headgate corner of 301, and
MC-8 , 790 feet from the headgate entry, have not subsided
since monitoring began. Angles between the mined-out area
and these points are 13 . 02° 25. 970 and 20.990 respectively.
Diagrams and calculations are included in Figure 21.
In an attempt to further tighten up the approximation of the
actual angle of draw in Coal Basin, calculations were simil-
arly made for five additional points. These points were
selected because there were a minimum of complicating factors,
such as contemporary two-seam mining, extraction areas in
different directions, and so on. These points, the assump-
tions made, results and interpretations are summarized below;
see Figures 22 through 26 for diagrams and detailed calcula-
tions.
TP-1 : This point is located near the center of longwall panel
101 , No. 1 mine. Longwall 101 in the area of the point was
• extracted in mid-1978 . It is assumed that the subsidence
determined to date, -1 . 94 feet, is due mostly if not entirely
to the extraction of adjacent longwall panel 102 , mined in
the fall of 1984 . Calculating from the 102 tailgate packwall
(101 headgate) , an angle of 7 .640 was determined (Figure 22) .
Given the apparent angles determined above, TP-1 is therefore
well within the angle of draw to be expected .from panel 102 .
TP-3 : No subsidence has been detected at this point, which
is located about 680 feet from the nearest full-seam extrac-
tion mining, the pillared are involving 4 and 5 North, Coal
Basin No. 5 mine. The angle calculated from the edge of this
pillar area to TP-3 is 21 .82° It can therefore be assumed
that this angle exceeds the actual average angle of draw in
the area. See Figure 23 .
MC-2 : This point is located 130 feet NW of the longwall 102
startline, over the 102 panel, and is 130 ft SE of the long-
wall 101 headgate. It subsided 1.04 feet between 1981 and
7/3/84 , presumably due mainly to 101 mining, but was nearly
stable by the latter date, having moved only 0. 01 feet since
the 1983 survey (this is well within the surveying margin of
error of +/-0. 05 ft) . Subsidence resumed in response to 102
extraction, begun in late 1982, and in fact the -0 .91-foot
. movement observed in the 1983 survey is likely due to 102
mining. In any case, the angle bewteen this point and the