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

C

3Br SURFACR SURSIDENCa
-0.000.0-0.1-0~ O 0.1 O•~ O./ 0.00
1 /
,H....
I
h ~
1
I
,
O ~-~~I~d7
@y. f.~.B SutniJena proab function (m).
where 8 is the critical radius or oae-half the critical width. S.., iS the
maximum possible subsidence over the center of the opening, .r is the
huriwnlal distance from the point of half-maximum subsidence, and J is
the distance between the point of half-maximum subsidence and the edge
of opening. Several profile functions have boon developed fur various caul
fields in the world (20). One of them, based on model and theoretical
invesdgatioru, iB
S ~)Sm„(1 - tanh(2r/B)) (9.4.2)
The unknown parameter 8 can be back-calculated from the measured
wbsidence, S, by solving fora in Eq. 9.4.2, dilfercntiadng with respect to i
x, and Betting s ~ 0,
B - S ~ (9.4.3) ;
where S',,., it the maximum slope observed in the field. It must be noted
that in Eq. 9.4.2, d is assumed to be zero; that is, the point of inflection is
directly above the edge of the opening.
Fur the Supcrcritictd cast, Eq. 9.4.2 still holds, except that 5,., ocean ' .
over tut area in the center of the subsidence trough, rather than at a point. '.
However, for the subcriliral width, the equation becomes more involved.
One method employs the Superposition of two critical width profiles. In
Fig. 9.4.7 the excavation A,A, has a subcritic:tl width w. Its induced
rurftue Subsidence profile can be determined by first assuming a critical
width opening with edge at A, and extending beyond A„ the profile
function of which S, is defined by Eq. 9.4.2. Similarly, a critical width
opening with edge at A, and extending beyond A, is an inverse of the
prcviuuB one, the profile function of which is S, aS defined also by Eq.
9.4.2. The resulting subcritical profile is
..
S ~ S, - S, ~ ls.,, { tanh 2 B 1° - tanh B~ (9.4.4)