Effect of lateral impact loads on failure of pressurized pip(3)

Effectoflateralimpactloads195

Fig.2(a)Thearrangementfortheunpressurizedtestswithafoundationsupportand(b)steel

platessurroundingthepipespecimenwithafoundationsupportinthepressurizedtest

2.22.2.1

MaterialstestingPipespecimens

Allthespecimensweremadeofcolddrawnseamlessmildsteelpipes,havinganoutsidediameterD¼57mm,awallthicknessH¼1.6mm,andaspanofpipeline2L¼570mm,respectively.Thespan2LwastentimestheoutsidepipediameterD,consideringthecharacteristicsofpracticalpipe-lines[3].

Staticuniaxialtensiletests[9,10]werecarriedoutforthecolddrawnseamlessmildsteelpipeÃ.Auniax-ialtruestress–truestrainrelation[11]forthepipespecimenswasobtainedwiththeassumptionofdoublelinearrelationship,wherestaticyieldstresssy¼772.6MPa,statictruerupturestresssrü1080.5MPa,andstatictruerupturestrain1Ãr¼67.6percentwiththeassumedYoung’smodulusE¼208GPa.

2.2.2Foundations

Thereweretwokindsofsoil,i.e.sandandkaolin,usedasthefoundationforthepipelines.Lightbrown neandmediumdrysandwasusedasafoun-dationtosupportthepipespecimensinthetest

Ã

Fourtensiletestswereconductedandtheaveragevaluesofthe

mechanicalpropertieswereused.

seriesA,ALP,AMP,andAHP,andasandfoundationdensityof1548kg/m3wasusedinthesetests.

Plateloadingtests[12,13]werecarriedoutonthesandfoundationinordertodeterminetheverticaldeformationandstrengthcharacteristicsofthesandinsitubyassessingtheforceandamountofpenetrationwithtimewhenarigidplatewasmadetopenetratethesand.Atypicaltestresultwasused,inwhichtheinitialtangentmodulusis7.14MN/m2andtheassumedPoisson’sratiois0.2[14].

Kaolin,alsoknownasChinaClay,isanaturalmaterialthatconsistsofvariableproportionsofvar-iousminerals.ThecommerciallyavailablekaolincalledPolwhiteTMB[15]wasusedasthefoundationsupportinthetestseriesB,BLP,BMP,andBHP.‘Light’manualcompactiontests[16,17]werecarriedout,wherethemoistkaolin,whichisamix-tureofkaolinpowderanddistilledwater,waspackedmorecloselytogether,therebyincreasingthedrydensityofthekaolin.Theobjectiveofthistestwasto ndtherelationshipbetweenthecom-pacteddrydensityandthemoisturecontentofthekaolin.Amaximumdrydensityof1.45Mg/m3attheoptimummoisturecontentof27.9percentwasnoted.

Triaxialcompressiontests[18,19]werecarriedoutonthespecimenstakenfromthecompactiontests.Thismethodincludedthedeterminationoftheundrainedstrengthofaspecimenofcohesive

soil

Proc.IMechEVol.220PartE:J.ProcessMechanicalEngineering

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