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p"u = 0"8 VE7x p:
<br />Wlrere:
<br />F\ = Tgtalverticalsoil pressrrre at the topof the pipe, psi
<br />--%r, = Criticalbuckling soilpressure at thetop of the pipe, psi
<br />E' * So-ilmodulus in psicalcrulated as therutio of the verti,calsoitpressure io,"*verlical soilstrain at a sipecifieddensity
<br />P6 = i-lydrostatic, critical-collapse" rjifferentialpressure,psi
<br />p. = llilPXP'rdpvad:" (1 *po)
<br />?a 6r\ F
<br />D _ f,LtC eL /QNc)\3\vur r/
<br />Where: (D*n7Dr*1 =.g5
<br />1.r, * Poission,s Ratio
<br />f" * .4S for Driscopiper
<br />E = stress and tinie'd,ependrtnt
<br />. tensile rnodulus erf'elasticity, psi
<br />_l:::"|f::lfrriat pressurized p,ips1lne, 15.-rr)re rnal pre$sure is us ually grbdt enoii$'f,"toexceed the externalcriticbl-bu,ckling Gii '-
<br />pJrysyre When a pressurized tine iJtL oesnut down for a perioci, watt Ouctiinshould be exarnined.
<br />^- whu'*'
<br />$fi, : $eH:,d3il:::lJ;"ff,T'0"' fe,ion
<br />bvwat,Bucx,-qsdpr = e-i**,lrpidffi*,'ili ,ilf::$:#1,fffi,1,:n^::?",r.:.dlp'- =ei{.i,?ip7Ji,ilidill."'". fiffi1!{iiru:m;:y_",:{::i;:,:TJ,;J,:1''safety Faetor * 15oo osi + lSAvhere 1500 psi is the pressurized pi[etines can u.l*"p* according t' thecompressiveyierd srrengtrt,jinri*iiJp'iil] P- - "'- iorowi^jiL;ffi;;;#,"J o^_#;;ffi:d,,rr:ru,X,ililtijlfi;,*. i'ffi:,:[ll:,ffi:[ffi],:1,, - " _ :
<br />'":lqlygi.lyr;['",s;f tn- e,rp-'*-ii. dti.irn-' rhe rop or the pipe, totar
<br />foil
<br />pressure' P,' atrvl lvlrrrL,r rdr wrrnK[no ot trre Fripe wall. Tests of nan- the top of the pipe, - - - v'| " r' \
<br />i:.',:Xriiilffig#?*?l'{!t'*9ff#[',ffifl",,,, ,
<br />fii;;J,,x,,-,",1,:,3il'"so
<br />in rhe pipewa' accordins
<br />lhe design of q Driscopipesysterp, a checliof non_
<br />g:fl1y:j^"^?napse may" odiu, ,ruei [n,i 6ir'g i,!ir,] i', [rq-v1tue of rhe bip;iil,il; ;Tiriiii_itv,
<br />93lP^{3ll$, gpnservative varue for iherv'
<br />rv rer ' ' '' n E, in psi.
<br />c;nucat,ouckting Bresst/re mary be oh[aine<j
<br />lltlq,fglluryinsapproxim"t*tornr,rldlii" guotzL
<br />pipe dianreters with the samer son ilih; Irrye Dependent Modulus ofsame buriarsituation have.lhe.",r* "iiiLar Fofyettrvtene Fipe u*l sG#cottapseandcriticatbucktingrunctuiancJ"' ;:r-:*.:::'- :
<br />collapse ,"4'",itir.r'oiilirii li,Jiiffi#:!"' r-rrrvs(rryfene rtpe vst stress lntensrty ('/3.4"n
<br />A
<br />500
<br />It?ffibT,T$tr,TillH[1,:'-T""*il"ifl
<br />slr6, Slross" pel
<br />cr3,1"F)
<br />OrlEcop,ps pcr ASTM O
<br />contactwiththepip"eandisc,u'pox*o-tJlio*nru,,',",:'ui:,,
<br />(sDR _ 1ii?T;1i,fi:JiJ.fffi3?'fi:'ffiF-m,Wrtnertns * i: -*-T -tr
<br />pressure, n* isarrov6cr to exoeeci *to6 pipu-"l,il toil 3- 9::gg up94 tne stress "Sa' an{ the estimatec1 timesiystern's critical bu<,-kli
<br />orarir rsl nntianoa *^.. :9^P"t-"-lsy1gt et.'it n J'p"0, ,o^rj:,1?ij,tl,:rn'pr_essurizaiion, use cnaita6lo'ij".r
<br />6: 6O,m0)
<br />E
<br />eulb 6o,cqr>
<br />t
<br />3r0o
<br />:E
<br />fu to,ooq>
<br />A
<br />700
<br />AA20O 3OO
<br />t
<br />1@
<br />ot lho plpe
<br />13 opproxlm6toly
<br />lhls nrodulu3,sceprndcnt u6ron p,u
<br />"rro'a lnionliiy "l'i tlm€ duratlpn of the 9lfgt6.
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