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<br />V!- DgsrOn Conslderafrons; Driscopipe performs
<br />ff ec tivety when buri ed oe.c auseb] i[u-"ni lity tu'''----deftecr in rhe inreraclirc pipu.*oit;i;j;,r, The pipeacrualy gains strengthlrorn tne suriou;oing sdil;iocan support adc,itionat soit toads, The soil #;;fd;"su rround ing the pipe wi lt. oompress,:, O'ef ect if iEii",]f Vunder the additionalfoads of tire drywJight ot bar:kfillabove the pipe, theweight of tne water-iafre
<br />saturating the soil,,the weightof nea,tytuitOings orstatic st^rctures, the \4/eig!"t oi'on"irre:rbad trucks andtractor$, railroad treight.tiains o,
<br />"nV "o*Oination ofatl these toads. In a r"texiote ,pip**6nFiisrem,
<br />tnepipe deflecrion is rhe same ejiilr,e siir.jinectionunder the load of the seconOerry OactcfittlnO
<br />"oysurJace loads.
<br />Whel the pipeline is laid in the trench, the soilenvelope is shoveled, washecl, ilusl",ed'oi oumpuointo Blace, in tayers. toan etevation ,6;;; ine top ofthe pipe. lt is udually compacted to a specifiedprocror density by rirechihi";f;;y#;rjil means, Asa d d i t io,n a I I aye rs 6 f s oit a re ba cf . n ri rii i n^tl' ir, e r re nc h,the w.eight of rhe soiloverthe ttril;ry,';;"*;actedbackfill is increased. This incnraseO weigh[slighttyggTplg.:sg: (srrains downwar ds.) ther Jorl.enverope.r ne amount of soil comp.resskrn i's ,*iaiJiio tnegjlenO.|r of rhe soitat a iiven c'eniiiy Jr;oio r,erntensity of the verticarsoir pressr,rr'e: sin;e-the soir isnot an. elastic materi al, tnis'cornpi,sss i-on"Jr. strain otre soilenvelope by the tinat oa6r<riili,""p"iin"nunt. n,. re soilenvelope is compress,U (,;trair[ij,'itbecornes furthercompacted" ln ii;;;;;i ltare, thesoildevelopsincreasddresistinceto*if r-e-vJrticatsoitpreesure untit it reaches static. equi f igriu; ;itnorrf u rthe r conrpres sion or stra in, .ft,rtJ is*tiil' ie Jction ortne corRpacted soil envelope, ' '- r! 'v rvqr
<br />measured
<br />the pipe
<br />ellipse by
<br />because it tUrthpr compacts the
<br />of the envelopes. As
<br />with the soil, it a very slighl:
<br />in the diameter an
<br />borizontal
<br />ly tess) amount
<br />is beneficial
<br />soiland thus
<br />Through
<br />the ring deftr
<br />based upon
<br />ln of Driscopipe
<br />Known oroDerti6
<br />presentecl later,
<br />be calculated
<br />of the pipe and the
<br />similar to lhe 'way
<br />arcn
<br />becornes a
<br />a fow grade
<br />,The venical
<br />il reliews
<br />8r'trJ'
<br />share o{ lhe
<br />thepipe.
<br />is measurecJ by
<br />of soilFrressure
<br />given soil
<br />26. The
<br />develops lateralsupport in a fashirsolt€butrnents offer support to a nbridge. The compaeted'soil actualrnasonry arch eyen though the soilmasonryusing goilparticles for bridecrease in diameter is beneficial
<br />jl.?fjpg of verriqar soit pressure cothus forces the soil to support tfrevsrticaltoad by arching 66tion ov
<br />9oqpl":.*iQility gf rhe soir envetog
<br />lhe SoilModulus, E,, which,is the'(stress) ro soif ddfleition lstrain) aicompaction denpifi as shown in Cdegree of compdciion of the soilerdetermined fronr a family of curv.es
<br />raooratory.tests. phart 26 is typicafand provides a generat guiO6 if tannot available to p{ot a tamity of curvsoiltype.
<br />he
<br />from
<br />can
<br />lVRiea{ Ferfonnance [-iinlits of BuriedFipes Due to Exrernafl soif en6rsi,re
<br />such curv€s
<br />data are
<br />fora specilic
<br />Deformation of flexible pipe criticalonly when the
<br />deflection ber which it can nb
<br />reaches that Doi of ring
<br />resiet anyincrease in sdil ling. By limiting r
<br />compaction. the
<br />deflection
<br />over athrough proper
<br />pipe is through the soil acros$ the soilarch around the pe, Thus the maintains itscircularin stabld soils is protected
<br />against long term
<br />llench Conett'ustion and
<br />8o
<br />H,= &
<br />FE9
<br />du,s$0"(5L*i: l-oose
<br />$oll
<br />35
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