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y~ <br />i ~1 JIi.I <br />11 <br />10 <br />. b <br />,.~ <br />~' <br />ti <br />S <br />_{ <br />._ .. .... ~_.. .~..' _-.- `I 1 <br />.F'i4. ti:2u: Stabiliq numlkn anJ ~q~pes ~o( ~ ._ <br />~~ slope failures for p 0. fAlttr Trreaghi ' <br />and Ptck (195ti).~ .. . <br />i .' i <br />''-' , ~ . <br />3 _ _ <br />!q'~ SO'~ - :0' ti0'.- SO' S0° '30' ~~ 20° .; 10' 0' <br />:-.. - - <br />. .>. ` '- <br />' _ -~"1'LiA1Tii'"h q~l'i l'L~I nItl1'~I ~., C11. N <br />?j <br /> <br /> ~ .~ ~h <br />~ <br />I _ <br /> <br />- <br /> <br />-- <br />_ <br />-./ 0 <br />aTrl ~ <br />_ •,° <br />4 ~ I • t Y ~; dI c <br />1 <br />_~t . _ t-~ ;. ._~" r <br /> --- --- ~-- 1 <br /> - ._. '.rte <br />~ +~~ i <br />! ..•I _ o <br /> . ? e~ r a <br /> <br /> <br /> <br />i - <br /> f ., <br /> <br />:. __ - <br />- <br />~ J! I <br />i ~ ~. <br />n ~•: _ <br />~ -. .5.32 <br />i <br />~~.. <br />~~~' I ~ . <br />~Tce circlce '. ., <br />I: -•-•- \Iidllnint circl,.•y <br />II ~--- JIOp2 elrelC~ ~ ~ ' <br />"t ~ - <br />+ _ ~ ~. <br />;' ..„pl.~ ~. I. The >intple >lo{+e >houn in Fig. S.2J h:ii a bright of 3.5 it :md :r <br />~: ! sertral 1o I horizontal. Tht >oil proptrtie> are a> follow; 1 = l'_5 Iwf, <br />!:.!tS. r _ ;thl p>f. Hy mtani of the icrbiliq~ chart, dettrmine the Lrctur of , <br />• a wnh resprct W failure. ' - . <br />:w;.ms Fora >lupe o! I ceniul to I honzontal we haet <br />~ ~ _ ,'..~ <br />nubility number for ~p _ 15 deg and ~ _. J5 deg ii. l L6 (Fig. 5.25). 7hw a[ . <br />. , ~ ~ N,• t N = 11.6! - ~ ~ ~ - <br />... - ~ c .. .. .. .... <br />~ - :i:e gistn conditions xro base ~ ~ ~ ~ ~ ~~ ~~ ~ ~ ' <br />+'` 1/, a I25 x 35 = fi?5 - ~ '.. <br />r. - 7LV - <br />' ~. .~iV <br />> <br />~~ ~~ti Ht'. N.7 til. rl l'ltJ.\].\1. 1'tilj _ ~ ''~- - -_ _ _~.' ~~~ , <br />- which is much smaller than N,~required for Ltilure. A ~itahility number of 11.6 can ' <br />_be reached if the height or dimity is incre:ued ur it the cohuion is reduced. Failure <br />' ~ : ~ Y e_Nt 11.6 x 700_ 232 ~cf <br />' - H JS p <br />_ - ...,,1 N.c ~.. 11.6 X 700;"' °' <br />•~The faCtar.of>afety islhcn the"derisiif (or htighQ [hnt the soil can support, dis'ided ' <br />by the gisen `density (or height): -.~ t :` ~• , _• ~ ~ ~ ~ ' <br />.` <br />.. .:.. _ <br />.The cu~e>ion required to make N, equal 11.6 i(y and !/ are as given is <br />t _ y„ = v5 x is =-3is ~r <br />N. .11.6 - P - <br />The factor ~of >afety may alio be the ratio o(dte Siveq cohe>ion wthat required fur <br />. ~ equilibrium, or ~ ~ ~ _ - <br /><, - .__ <br />- ~ : •F•'= )~ ° 1.86. '. <br />It >hould be noted tha[~thi> safeq~ factor i; for'cohe>ion only. The s.dur of o usrd <br />to enter the chart is 15 deg; hen{e the s;deq' factor with respect to o is l.0. There- <br />. fort the s'alue of L$5 i> not the_(uctur .of >:dcty defined by Ey. (S.Sn), which wn, <br />>idtn the entire >hcar _>trength... ~~. ~."'., . ~ - _ ., _ <br />The >a(ety factor that appliei equally to both c and o may bt ecpre»ed :n ~ - <br />-, . - r.. <br />c ,~ tan S... ,. <br />To calcul.itt this >a(ety factor, we lust taim:ue F, to be 1.60. Thrn ~- <br />tano _ utn IS° _ - <br />F, 1.60 ` O.I68 <br />. This correspond> to a~0 0(9.S deg. N'e enter the chart (Fig. 8.25) s.~ith C of 9.5 dig <br />. ~ and find :.. ,. .. ~ , _ ... ~ ~ _. ~ .... <br />. ~. ~ 125x35 - ~ -~ <br />Thus~we can have factors of safety of 1.60 for b and 1.47 for c instead of LLB) for ., <br />~ and I.85 (or c. 1(wt want the nano safety factor for r and 0, we must revise our~,~ <br />first estimate of 1.60. Subsequent trials give a value of 1.49 for F, that holds Cor ~~ ' <br />both c unJ p. <br />