PERMFILE112504

• Permit No: C1981012
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 24 SUBSIDENCE CONTROL PLAN
• Media Type: D
• Archive: No

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SURFACE SUBSIDENCE
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~' wrfea point and reduces to 2 to 3% if the face has passed the critical
width. The rate of face advance determines the time needed to pass
;~, through the critical width. As long as the face is still within the critical
width, further wbsidence is expected.
However, Brauner (13), citing Russian data, stated that in addition to
the tare of advance and size of critical area, the duration of surface
subsidence depends on strata conditions, depth o[ extraction, kinds of
packings, and previous extraction and that it ranges from several days Io
' several ycafx. The duration is longer fur (hick-bedded or stronger uvcr-
• burden, for greater depths, and for complete caving. For a small extrao•
•. lion area of a relatively mobile overburden mined in a very short time, the
rate of subsidence ie proportional to the difference between the final
subsidence S and the instantaneous subsidence S,:
~t ~ c(S - S,)
I, ,
4
I
the solution of which is
(9.2.1)
S,/S ~ C ~ 1 - e-~ (9.2.2)
whero C is a time factor and c is a constant characteristic of the strata. A
typical C curve for soft strata is illustrated in Fig. 9.2.g.
In the United States, earlier studies (10, ll) showed that subsidence

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