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Z/-+ <br />Based upon the pipe SDR and the value of .the <br />iliu-*ir,vi"n* <br />"rnobutus <br />of elasticity' E'.calculate the <br />L'pLl #vO to*titic, c ritical -collapse ditf erential <br />Design bY Deflectim:deflection is <Jefined t.- <br />as the ratio the vertical in diameter tothe <br />original It is often asa <br />buried Driscopipe is <br />more than) ihe veflioal <br />of the soil around the PiPe. <br />Design bY deflection the abitity of <br />toacconrmodale.structuml <br />2.32 (E) <br />]sEr <br />5. Calcutate the soil modulus. E', by plotting..the total- <br />externatsoil pressure, P,, against a.specified soil <br />Oensittl to Oeirive the soil strain as shown in the <br />exam[le Problem on Chart 26' <br />6. Calculate the critical buckling pressure at the top <br />of the PiPe bY the formula: <br />P66 = 0^8 \€xE <br />7. Calculate the Safety Factor: S'i = Pce. : P'' l"}-u;i;iappjicatioris, a eafety factor of 1'0 mav be <br />ffi;ilirE!-u minimum trecalse of the margin.of <br />;;ffi;t""i.leo ov the arching action of the soil" <br />Ho*euer, Driscopipe endorses using a more <br />tJn;;#tid vatue approaching or exceeding a <br />2.0 safetY factor. <br />8. The above procedures could be reversed to"' iil;ttil" 'iiinimurn <br />pipg $DR req-uired for a given <br />*iil oi"tsun" and an estimated soildensity' <br />Howeuet this prooedure should permit the <br />;rufi#t";fiimize the svstem design quicklv bv <br />eiirnining seVeral combinations' <br />ChartZti <br />Fi6i <br />"f <br />Ventical Stress-strain Data for <br />ripical fnench tsacktll! (Except Clay) <br />frbnn Actual Tests" <br />EXAMFLE <br />Flnd: E'@ 2000 PSF and 009c Denslty <br />p9111uh; I'e P1/e3 <br />b-.iiiriiil-., e;=iooo psrl.olg = i1111'l PSF=771 psl <br />N;;'rn;;;*"" thown on thls chart sro Eamplo eurvec for rgranrlar mll' <br />iiil;;'il;r ;i -oll rrc uead tor bockflll luch ac Gf'v or cta! looto cuwet <br />il;l,i';T;;;;pcd ttom laborato'v trit dett tor, th6 mstcthl u3cd' $:oll <br />;i#;;;;;;i;ltnan +ooo pst mav bo oxamtncd-bv'cxttatolrfns tho <br />sloeo ol tho cufvc o, uy g"nu'uttng iurvcs Oy tcsltng ot thosc hlghcr roll <br />i'i'"iu-*i, *uu"lte cir6r ot curv6s ls abouihalt thc itstanc! bctween <br />adlaccnt liner. <br />pressure, Ps: <br />Pc= <br />. Ring deflection. <br />elv the.same as1 <br />32.5 <br />26.0 <br />21.0 <br />19.0 <br />17.Q <br />15"5 <br />'13.s <br />11.0 <br />ring <br />a functiori of the allowable <br />distress,vertical <br />deflection <br />b en$ure <br />of the PiPe <br />with lower <br />less. For <br />resist the soil <br />can easilY lirnited tothE <br />of the backfill <br />allowable <br />$DRs are <br />Chart2T <br />SDR <br />the buried <br />wTlbe/ess &han <br />See Ohart27. <br />of SDB,llre <br />which this thickerwallto <br />actualring de{lection <br />lar values bY Proper <br />rd the PiPe, The <br />ion of the soil. a <br />.DxignbY ting I <br />mofvertical'so,lslfiarn i <br />atlowable ring dallection J <br />tabulation shows that <br />etlowablo defleotion is <br />8,10/o <br />" 6.5% <br />5'2o/o <br />4.7% <br />4.2o/o <br />3.97o <br />3,40/o <br />2,7% <br />of polyethyleno PiPe is <br />roential strain In the <br />conservative limitof <br />outer surface of the <br />;tion of the PiPre 'ring' <br />forthewrrizue <br />Allowable <br />Derllectlotl <br />understood bY <br />diameter but <br />\ <br />The <br />outer surlgce of the PiPe^v <br />1 -1Vz% talrgentiat strain {n <br />oioe wall dile to verticaldef <br />b,i soil cornpression cart be <br />c6mparing two P[Pes of the <br />ditferent rlall thickness, <br />€ <br />9cmoptI.€'oI moo <br />oa,?o <br />? rooo <br />frd <br />Duax <br />o/o Ring <br />NOT€: 5./. deflcctlon dGca6!tLa <br />decreese$ llo$'area bY 1%' <br />=('- <br />by %%.'t0t6 doflgctlofl