PERMFILE134372

• Permit No: C1981016
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: Western Portal Re-Opening & Roof Control Plan
• Section_Exhibit Name: APPENDIX XXII And Appendix XXIII
• Media Type: D
• Archive: No

'_' 1 ;1
•
lien
IIN
i
to
o = .l;-
{il°
°o° an° cn^
a
lal
u=1

ti li l'. n.ll ti L11~ .1 \.\ 1. 1' 411 ~ '~~1
r,llculatiuns made with logarithmic spiral and circular arc :li failure iurfaccs
give very close results. Extensive suuhes by Swedioh engineers of slope lailures
in clay during the rely p;ut of this cenuu~y ;Ilse revcllal th:u the lailure
surface closely approaches the circular arc. The ^nalysis of slope stability
using a circular slip surface was developed by Fclleniw (19}ti) ;uul others
and is often referred to :IS the Sredieh cindr nlrrhod. Figurt S.?? shows the
displacement of the soil nws's produced by a s'lupe failure.
F,
II
r•
(nl

e
!.
r
o dt'.
~tl
n/'
11
, ~ ````
.rl all
Fip. hal. Circuhlr-ale ntelhod of olope analysis.
an° au° liu-
0
,6)
Pig. ts.?n. l3a:u ing capacity numhen litr found,l-
liom with inclined loads. [After Ateyerho0~(19i3).]
1•t.s.'rll' tart t.tuntl at. ru.

-n.rrr = n
~~ ---u/rr = l
`
.

~ ~

an° ~~ .
~
,

au° m = as°

Cirrulur arc merGod. Figurt 8.? I(u) shows a soil mass bounded by the
slip surface abet/. Since the circular arc is nn assumed ;lip surface, iti position
is not determinate. The arc obcd is therefore an arbitrarily assumed arc. The
furcts acting un the soil m;us obcd arc the weight of the soil muss II' and the
force on the failure surface. The farce un any element Lc of the slip surface
is composed of a normal component dF„ and shear or tangemiul component
r/F, parallal to it. At failure, dF, must be equal to the shear strength of the
soil as expressed by Eq. (7.?), which in this case can be written as
rlF,=cdf+dF„ulna