INSTALLATION OF PIPE AND TESTING OF PIPE OF PIPE AND TESTING OF PIPE BACKFILL ... for the applications on your project. 1) Metal pipe ... joined with approved coupling

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  • VDOTSoilsandAggregateCompaction

    2016v1.0Chapter4|1

    4

    INSTALLATIONOFPIPEANDTESTINGOF

    PIPEBACKFILL

    LEARNINGOUTCOMES Understandbasicpipeandsoilconceptsandhowtheyrelatetopreconstructionissues Understandfundamentaltrenchconceptsandpipeinstallationprocedures Understandinspectionrequirementsandbackfilltestingfrequenciesandprocedures Understandthebasicprinciplesofpavementdrainconstruction

    INTRODUCTIONAwell installedpipe should stay in service50 to100yearswith littleorno repair.VDOT states75years forhigherfunctionalclassificationroadsand50yearsforlowerfunctionalclassificationroads.Properinstallationisessential to pavement performance as it increases bearing capacity, increases service life and lowersmaintenancecosts.

    Figure4.1:PrecastConcretePipe

  • VDOTSoilsandAggregateCompaction

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    BASICPIPEANDSOILCONCEPTSThetypeofpipeselectedforaparticularapplicationdependsonmanyfactors.Thefunctionofthepipe,thesoiltypepresentinthetrench,thedepthofthepipecanallinfluencethetypeofpipeselected.SeethefollowingtableforVDOTrecommendations.

    Whenplanningapipeline installation, thereare2key functions thatwemustdesign thepipeline toprovide.Whatarethosetwofunctions?Clearlythepipeneedstofunctionasaconduit,asthewholeideaofapipeistomove liquid inacontrolledmanneranddirection.Andthepipemustprovidestructure,because ifthegroundabove thepipe collapses then thepipe canno longerperform as a conduit. Havingoneof these functionswithouttheotherisworthless.

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    Culvertsaregenerallydesignedfortheloadstheymustcarryafterconstructioniscompleted.Constructionloadsoftenexceeddesignloads.TheseheavyloadscancauseconsiderabledamageinflexiblepipesandcancauseDloadcrackinginrigidpipes.Additionaltemporaryfillisneededtoprotectthepipefromconstructionloads.Minimum/MaximumCover

    AllCulverts 24minimumcover

    Absoluteminimumfillheight(12)

    Exceptforentrances(9minimum)

    Allpipeshouldhavethreefeetofcoveronitbeforeconstructiontrafficisallowedacrossit.

    StructuralSystem StructuralSystem

    Figure4.2a:ReinforcedConcrete Figure4.2b:FlexiblePipe

    3ft.

    Figure4.3:MinimumCovertoAllowConstructionTrafficoverPipe

  • VDOTSoilsandAggregateCompaction

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    ThefollowingtablesgiveVDOTspecificationsformaximumheightofcoverforsometypesofpipe.

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    PRECONSTRUCTIONISSUESPriortoconstructionthepipedeliveredtotheprojectshouldbeinspectedandverifiedtobethepipespecifiedfortheproject.Areviewoftheproperminimum/maximumheightofcoverforthespecifictypeofpipeshouldbecompleted.Inspecthowthepipeisbeingstoredonsitetoensurenodamageisbeingdonetothepipepriortoinstallation.Verifyingthatthecorrectpipehasbeendeliveredfortheapplicationsonyourproject.

    1) Metalpipegauge:Examples12,14,16

    2) Metalpipecorrugationdimensions:Examples22/3x;3x1

    3) Concretepipestrength:ExamplesClassIII,IVorV

    4) pHandResistivityneedstobeknownbydesigner

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    5) Maximumheightofcover:Maximumheightforeachtypeofpipemustbegiven

    Compareinformationfromdrainagesummarywithmaximumcoverchartforpipetobeused

    CheckstandardsforminimumheightofcoverMeasuringMetalPipeCorrugationexample3x2Examplesofconcretepipestamp:Theytypicallyincludemanufactureddate,diameter,pipetype,class,placeofmanufacturing.

    Pipeshouldbestored inanoutoftheway locationwhere itwillnotbedamaged.Thepipeshouldbestackedand chocked to avoidmovement of the pipe. Pipe should never be stacked on the bells as they could bedamaged.

    3

    2

  • VDOTSoilsandAggregateCompaction

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    TRENCHFUNDAMENTALSTrenchTerminology

    Thebeddingistypically48thick.Thetopfewinchesshouldbeslightlyyielding(loose)andfillthecorrugations.Often, shaped beddings are used to insure proper placement and compaction ofmaterials under the pipehaunch.TheinitialbackfillofselectTypeIbackfillprotectsthepipeduringinstallationfromimpactdamageandextendstothespringlineofthepipe.Inarigidpipe,thiszonehaszeroeffectontheloadcarryingcapacity.Inaflexiblepipe this zonemustprotect thepipe fromdistortionsdue to loadingextend to12 abovepipe.This zonecontainsthesameselectqualitybackfillmaterialasinthehaunchzoneforflexiblepipe.Generally excavated embankment material is used as the final backfill. It is placed in 6 loose lifts andcompacted to4.For flexiblepipe thisbegins12over topofpipe forsmallerpipeand18 forpipe54andlarger.ThefollowingdrawingprovidestypicalVDOTstandardsforpipebeddingandbackfill.

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  • VDOTSoilsandAggregateCompaction

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    INSTALLATIONPROCEDURESGeneralproceduresforpipeinstallation:

    1) Locateutilities

    2) Excavatetrench

    3) Explorefoundation

    4) Placestructuralbeddingmaterialtograde.Donotcompact.

    5) Installpipetograde

    6) Compactstructuralbeddingoutsidethemiddlethirdofthepipe 7) Placestructuralbeddinginlifts

    8) Complete structural backfill operation byworking from side to side of the pipe, differential not toexceed24or1/3sizeofpipe.

    LocateUtilitiesPriortoexcavatingthetrencharea,allutilitiesshouldbelocatedbyaqualifiedcontractor.ExcavateTrenchPropertrenchwidthswillallowforpropercompactionalongsidethepipe.Trenchwidthsmaybevaried,basedon the competency of the insitu soil, backfillmaterials, compaction levels and loads. Trenching should becompletedinexistingsoilswithsidewallsreasonablyverticaltothetopofthepipe.Itisnotappropriatetoleaveabenchofnativesoilalongsidethepipeduringconstruction.Thecompactionequipmentwillrideonthenativesoil andnot allow forproper consolidationofbackfill. Forpositiveprojection embankment installations, theembankmentmaterial should be placed and compacted to aminimum of one foot above the pipe and thetrenchexcavated intotheembankment. Thispreventsdisruptionofthebackfillenvelopewhenremovingtheshoringortrenchbox.ExploreFoundationAstablefoundationmustbeprovidedtoensureproper lineandgrade ismaintained. Unsuitablefoundationsmust be stabilized at the engineers direction. Unsuitable or unstable foundations may be undercut andreplacedwithasuitablebeddingmaterial,placedin6lifts.Othermethodsofstabilization,suchasgeofabricsmaybeappropriatebasedontheengineersjudgment.Thefoundationistobeexploredbelowthebottomoftheexcavationtodeterminethetypeandconditionofthefoundation. Theexploration shouldextend toadepthequal toper footof fillheightor8,whichever isgreater.Ifitisaroutineentrance,orcrossoverpipe12to30indiameter,thatistobeinstalledunderfills15feetorlessinheight,noexplorationisneeded.TheContractorshallreportfindingsoffoundationexplorationtotheEngineerforapprovalpriortoplacingpipe.Whenstandingwater is inpipefoundationarea,No.57stonecanbeusedasabackfill inthesubfoundation.No.57 stoneMUSTbe cappedwithaminimumof4 crusher runprior toplacementofpipeorbox culvert.CompactiontestingonNo.57stoneisnotrequired;seatstoneintrench.

  • VDOTSoilsandAggregateCompaction

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    PlaceBeddingStable and uniform beddingmust be provided for the pipe and any protruding features of its joints and/orfittings.Themiddleofthebedding,shouldbelooselyplacedandnotexceed8inches.Thelooselyplacedcentersectionof thebeddingallows thepipe to seat itselfandhelpsminimizepoint loads. (RoadandBridgeSpec.Section302.03Procedures)Whenliftholesareprovidedinconcretepipeorprecastboxculverts,theContractorshallinstallaliftholeplugfurnishedbythemanufacturer.Afterpipeinstallationandpriortobackfilling,plugsshallbeinstalledfromtheexteriorofthepipeorboxculvertandsnuglyseated.InstallPipeThegradeofthepipeshouldalwaysbemonitoredduringinstallation.Whenjoiningpipe: Beginatthedownstreamend(Bellfacesupstream)

    Ensurespigotandbellarecleanandfreeofdebris

    Properlylubricatespigotandbellwithpipelubricant

    IsContractorawareofthemaximuminsertionangle?

    Fullyinsertpipe.(MakeaMarkonOutsideofPipe)

    Movingpipearoundafterjoiningmaycausepipejointtoworkapart.Rigidpipeproperlyfitted,sealedwithrubber,preformedplastic,masticgasketsFlexiblePipeproperlyalignedandjoinedwithapprovedcouplingbandsJointPerformanceTerminologySoilTight:AjointthatisresistanttoinfiltrationofparticleslargerthanthoseretainedontheNo.200sieve.Soiltightjointsprovideprotectionagainstinfiltrationofbackfillmaterialcontaininghighpercentageofcoarsegrainsoils,andareinfluencedbythesizeoftheopening(maximumdimensionnormaltothedirectionthatthesoilmayinfiltrate)andthelengthofthechannel(lengthofthepathalongwhichthesoilmayinfiltrate).SiltTight:AjointthatisresistanttoinfiltrationofparticlesthataresmallerthanparticlespassingtheNo.200sieve.Silttightjointsprovideprotectionagainstinfiltrationofthebackfillmaterialcontainingahighpercentageoffines,andtypicallyutilizesometypeoffilteringorsealingcomponent,suchasanelastomericrubbersealorgeotextile.LeakResistant:Ajointwhichlimitswaterleakageatamaximumrateof200gallons/inchdiameter/mile/dayforthepipelinesystemfortheprojectspecifiedheadorpressure.

  • VDOTSoilsandAggregateCompaction

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    TypesofJointsforConcretePipeTongue&Groove:Abell&spigottypejointwithstraightwalls(flushbell).Thejointconsistsofatongue(maleend)andgroove (femaleend)withnodefiningareas forgasketmaterialplacement. Rubbergasketsmaybeusedwhenthejointslopeisfivedegreesorless,howeveritisusuallylimitedtomasticorbutylsealants.BellandSpigot:Apipewithaflaredbellhastheoutsidediameterofthebelllargerthantheoutsidediameterofthepipe. Anotheroptionwith the flaredbell istheModifiedTongue&Groove,orBabyBellwhich isacrossbetweenastraightwalledT&GandaStandardBellitdoesnotstickoutfromthebarrelasfarasaflaredbell.ConfinedORing:Thefirstrubbergasketjointdesignesta

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