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Vibration compaction characteristics of rock filling embankment

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Vibration compaction characteristics of rock filling embankmentof,OF,rock,Rock

    Vibration compaction characteristics of

    rock filling embankment

    J.Cent.SouthUniv.Techno1.f2009)16:1034—1038

    DOI:10.1007/sl1771-009-0171-7

    Vibrationcompactioncharacteristicsofrockfillingembankment

    杨明杨刘广杨明杨YANGMing—hui(),LIUGuang—xuan(),ZHAOMing_hua()

    (CollegeofCivilEngineering,HunanUniversity,Changsha410082,China)Springer

    Abstract:Thedynamicmodelexperimentoftherockfillingembankmentwascarriedouttoinvestigatethevibrationcompaction

    mechanism.Therockfillingmaterialswerecompactedbytheplate—

    vibratedcompactor,andthecharacteristicsoftherockfilling

    materials,suchassettlement,pressurechangeandresponsewaveform,weremeasuredbythedynamicearthpressuregaugeand

    aceeleromete~Moreove~anewmethodfordetectingthecompactnessoftherockfillingembankmentwasproposedbasedonthe

    maximumdrydensityandmodulusofdeformation.Theresul~showthattheprocessofvibrationcompactionincludescompact.

    elasticdeformationandloosestages,andthevibratorypressuretrailsferstothesurroundingsfromthevibrationcenterinnon.1inear

    rule.Furthermore,thetestresultsobtainedbythepresentmethodarebasicallyinagrcementwiththoseobtainedbythetraditional

    meod,andthemaximumrelativeerrorbetweenthemisabout0.5%.

    Keywords:rockfilling;embankment;modeltest;vibrationcompaction;compactnesslIntrOducti0n

Duringtheconstructionofthehighwayin

    mountainOUSareacharacterizedbyrocksandsoil,therockfillingembankmentisthemajorstyle.However,thekeyissueoftherockfillingembankmentisthequalityofthecompaction.Therefore.itisimportanttoinvestigatethemechanismofvibrationcompactionoftherockfillingembankment[1-6].Thebasiccontrolcriterionofthequalityoftheroekfillembankmentcompactionisthecompactness.However,mostofthestudiesandthetestcriteriaarebasedonthewaterorsandfillingtest,whichtakesalotoftimeandlaboranddamagestheroadbed.andtherearetheteststandardandthefillingstandardfortherockfillingembankmentingeotechnical

    engineering[7—8].Obviously,itisimportanttofindasuitabletestmethodforrockfillingembankmentin

    practice.LIUeta119usedtransienthammer-impacting

    technologytomeasurethecompactnessofthesoil.LIetalfl01appliedthedirectshearwavemethodtoevaluatingthecompactnessofthesubgrade

    nondestructively.VGHELAf111proposedtheresonantcolumntestforthedeterminationofelasticmodulusofthecompactedsubgradesoils.Moreover,theadditionalweightmethodwasappliedtomeasuringthedensityof

    therockfillofthedam12-131.I,NSS0Nand

    KARASALO[141presentedasimplemethodtoestablishthefrequencyscattercurveofRaleighwaveindifferentmedia.KIMand151usedspectralanalysisof

    surfacewavesmethodtoevaluatetheground

    densification.MALISCHEWSKYl61testedtheearth

    fillingembankmentandestablishedtheconfirmedformulaofthecompactness.However,theaccuraciesof

    theabovemethodscannotmeettherequirementofengineeringifthefillingmaterialisrock.Accordingtothepracticeofengineering,a

    1aboratorytestonthevibrationdeformationpropertiesandmechanismoftherockfillingembankmentwascarriedout.Themechanismofvibrationcompactionwasachieved.Moreover,anewmethodfordetectingthecompactnessofrockfillingembankmentwasproposed.2Experimental

    2.1Parametersofexperiment

    Accordingtothesimilaritytheory,themodeltestwascarriedouttoinvestigatethevibrationcompactionoftherockfillingembankment.Fig.1showsthedetailsoftheexperimentoftherockfillingembankment.ThebasicpropertiesoftheprototypeembankmentandmodelareshowninT-able1.

    2.2Experimentapparatus

    2.2.1Vibrationcompactionequil:Iment

    Vibrationcompactionisthemosteffectiveprocesstocompacttherockfil1.Themassofvibrationrollerismorethan12t.Inthisexperiment,twokindsofflatpanelvibrationmachineswithdimensionsof50cm×60cmwereused,thevibrationforcesofthesetwomachineswere10and201(Nrespectively,andtheirfrequencieswere3000r/min.

    Foundationitem:Project(50708033)supposedbytheNationalNaturalScienceFoundation

    ofChina;Project(20070532067)supportedbyDoctoral

    FoundationofMinisyofEducationofChina

    Receiveddate:2009-01-26;Accepteddate:2009-05-25

    Correspondingauthor:YANGMing—hui,Associatedprofessor;Tel:+86731—

    88821654;E-mail:yamih@126.corn

    J.Cent.SouthUniv.Techno1.(2009)16:1034—10381035Preserv

    rOOm

    l—l—I?

    II}/

    Soil-ma……

    一『1000l

    6600.

    I'i

    .

    7000.

    (a)

    nkment

    Preservedroom

    

    (c)

    Fig.1Experimentmodelofrockfillingembankment(Unit:mm):(a)Crosssection;

    (b)Sideview;(c)Topview

    Table1Mainparametersofmodelexperimen

    2.2.2Excitermachines

    Twokindsofexcitermachineswereused:one

    excitergeneratedsimpleharmonicverticalvibratoryforce,withthemaximumvalueof100kN,andthefrequencywas30—60Hz.Moreover,thepoweramplifierandthesignalgeneratorwereapplied.Otherexciterusedthelightmassdynamicpenetrationapparatusandthehammersensor.Thisexcitercouldgenerateimmediateimpulseforcethatwastransmittedforwardinthepulsestyle.

    2.2.3Signalcollectionsystem

    Thepiezoelectricaccelerometerwasusedtocollect

    theRayleighwave,whichwasinstalledonthemagneticbasebytheagglomerant.Tlhemachineswerechargedbymeamplifier.andthesignalcollectorwasusedasthecorrelativeconfigurationapparatus.

    2.3Experimentalprocedure

    Twosoil—manometerswereplacedatthebottomofthemodel,andthereckembankmentwasfilledandcompactedwitheachfloorof20em.Thespeedofcompactionwascontrolledbythevibrationandthenumbersofrolltimeswere2,4and6,respectively.Duringtherolling,thedataofsoil—manometerwerecollected,andthethicknessesoftheincompactlayerandthesettlementofthecompactionwereobtained.Based

    onthesevalues,10testpointsweresett'.1elevel

    measurement,whichwereusedtocalculatethemeanvalueofsettlement.

    Theheightsoftheembankmentmodelwerefilledtobe4O.80and120cmrespectivelybythecompactionofincompactlayer.Thentheexciter,thedynamicpenetratinghammerwithlightmassandthehammersensorsettledonthestiffbearingplate,wereadoptedtocarryoutthedynamicloadexperiment.Duringtheprocessofexcitation,theexcitationfrequencywasaajustedfrom3Oco60Hz.andthedistanceoftwoaccelerometerswassetonthesamelines.Theexcitationpointswereadjustedfrom0.5to3.0m.Moreover,thepiezoelectricaccelerometercollectedthecorrelativesignalsofthesoil—manometerandaccelerome:ter.ToinvestigatetheeffectsOfmemoisturecapacity,whentheheightsoftheembankmentmodelwerefilledt040,80,and120cm,respectively,thecompactness

    waterfillingtestsoftwodifferentloc~ionswerecarriedoutatthesametime,andthentherockdiggedinthewaterfillingtestwasusedtomeasurethemoisturecapacity.

    3Resultsanddiscussion

    3.1Deformationcharacteristic

    TherelationshipbetweenthevibrationcompactiontimesandthesettlementoftheembankmentisshowninFig.2,indicatingthatthevibrationcompactionofrockcanbedividedintothreestages.Thefirststageisthecompactionstage.Inthisstagethescalementoftherockfilllayervariesobviously,andthecompactness1036J.Cent.SouthUniv.

    Techno1.(2009)16:1034—1038

    growsrapidlywiththeincreaseofcompactiontimes.Thesecondstageistheelasticstage.Thevariationofsettlementislittleandtherockfil1iselasticinthisstage.andthecompactnessisbasicallystable.Thethirdstageisloosening.Thecompactnessreducesinthisstage.Therefore.itisshownthattheoptimumvalueofcompactiontimesforrockfillingembankmentis5or6.Compactiontimes

    Fig.2Relationshipbetweensettlementandcompactiontimes3.2nansmissionofvibrationforce

    Generally,theembeddedsoil—manometersin

    embankmentcanmeasuretheverticalsoilpressureatdifferentfillingheights,differentgravityloadsandtwokindsofvibratorlpads.Inthiswork.thesoilpressureswerethepeaksoftheresponsecurve.

    Fig.3showsthedistributionofthehorizonta1additionalsoilpressureoftherockfillingembankmentat

    anexcitationamplificationof20l(N.Fig.4showsthedistributionoftheverticaladditionalsoilpressureunderdifferentplumbdistancesawayfromthevibrationcentenItisshownthatthevibrationenergyisnonlinearlytransferredfromthevibrationcentertothesurrounding,InFig.3.whenthehorizonta1distanceismorethanl00cm.thehorizontaladditionalsoilpressureis0.4kPa,whichisnearly0.6%oftheoriginalvibratoryload(67kPa).InFig.4,atadepthofhigherthan120cm,verticaladditionalsoilpressureis6.72kPa.whichisDistance/cm

    Fig.3RelationshipbetweenhorizontaladditionalsoilpressureandhorizontaldistanceawayfromvibrationcenterSoilpressure/kPa

    Fig.4Relationshipbetweenverticaladditionalsoilpressureandfillingheight

    nearly10%oftheoriginalvibratoryload(671Oa).Therefore,theinfluencingrangesofrockfillingembankmentareapproximately2.4timesofloadwidthinverticaldirectionand2.0timesoflpadwidthinhorizontaldirection.

    4Newmethodofdetectingcompactness

    4.1Calculationmodelofcompactness

    Thetraditionaltechniquefordetectingcompactnessoftherockfillingembankmentisthewaterorsandfillingtest.However,itmaydestroythesubgrade,andthedetectingspeedistooslowtomeettherequirementoftheconstruction.Therefore.itisveryimportanttoproposeanewrapidtechniquetodetectthecompactnessoftherockfillingembankmentfl71.Toachievethisaim,anewcompactnessmodelisestablishedaccordingtothe

maximumdrydensityandmodulusofthedeformation.

    Thebasicprocessisasfollows.AccordingtotheBoussenesqtheory,thesettlement

    ofsubgradesurfaceisl8-191:

    

    w==

    +b

    wherePistheconcentrated1pad;parametersthatcanbeobtainedbytheresultsofstaticconepenetrationthefiat.bottomedcircularprobeiswrittenas

    1——2/.t

    2ro(1)

    6:—(1—

    -

    

    n

    

    o—

    )—

    E

    .

    o—

    zro

    1"'

    (1)

    aandbarefitting

    thelinearfittingof

    test.Iftheradiusof

    r0,aandbcanbe

(3)

    where/tisPoissonratio;E0isthemodulusofdeforma—tion;and0istheinitialvoidratioandisdefinedas?(4)

    Therefore,thecompactnessofrockfillingu|./LIc

    uJ,lulu?^llBlng:=1

    a=??oJal10?

    杨杨二:!!!:!!:!!

    embankmentKcanbewrittenas

    1037

    K:Pm(1H0)

    ×100%(5)

    Pdmax

    wherePmisthedensityoftherockfillingmaterials;andPdmaxisthemaximumdrydensityobtainedbycompactiontest.

    4.2Testverifieation

    Inordertoveilfytherationalityandfeasibilityofthenewtechnique,thecompactnessofthreetestingpointswasdetectedbythenewtechniqueandwaterfillingtest.Thebasicparametersaredeterminedas:E0=23.65MPa,pm=2.67g/cm,and=2.46eCcm.Parametersaandbareobtainedby1inearlyfittingtheresultsofstaticconepenetrationtest.ThelinearfittingcurvesareshowninFig.5.andthecompactnessisP—i/105N

    ,)t/105N

    '/105Ni

    Fig.5Linearfittingfordifferenttestingpoints:(a)Point1;

(b)Point2;(c)Point3

    obtainedbyEq.(5).ThecomparisonofcompactnessbetweenthenewtechniqueandwaterfillingtestisshowninT{lble2.Themaximumrelativeerrorbetweenthemdoesnotexceed0.5%.

    resultsofthenewmethod

    traditionalmethod.

    whichindicatesthatthe

    agreewiththoseofthe

    Table2Comoarisonforcomoactnessatdifferenttestingpoints5Conclusions

    (1)Thecompactnessincreasesrapidlywiththeincreaseofthecompactiontimesduringthevibrationcompact.Itisstableifthecompactiontimesreaches5or6.Thereexistsanoptimalcompacttimesaffectedbytherockparametersandcompactionenergy.

    (2)Theinfluencingrangesofrockfilling

    embankmentareapproximately2.4timesoftheloadwidthinverticaldirection.and2.0timesoftheloadwidthinhorizontaldirection.

    (3)Anewmethodfordetectingcompactnessforrockfillingembankmentisproposed,whichcanimprovethetestingspeedandreducethedamagetotheroadbed.References

    CHAIHe~un,CHENQian-ying,KONGXiang—yun.Overviewofsoil.stonehighembankmentconstructionstudy[JlRockandSoilMechanics.2004,25(6):1005-1010.

    WANGPeng.GUACheng—chao.TheapplicationofPFWDinsub.gradecompactnesstestfC1//GeoHunanlnternationalConference.

    Changsha,2009:84-91.

    CATTANEOP,Optimalmeasurementofsignalovernoiseratio

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