【astm標(biāo)準(zhǔn)】g 57 - 06 (2012)

1、Designation:G57?06(Reapproved2012)StardTestMethodfFieldMeasurementofSoilResistivityUsingtheWennerFourElectrodeMethod1ThisstardisissuedunderthefixeddesignationG57thenumberimmediatelyfollowingthedesignationindicatestheyear

2、ofiginaladoptioninthecaseofrevisiontheyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperepsilon()indicatesaneditialchangesincethelastrevisionreapproval.1.Scope1.1Thistestmethodcoverstheequipme

3、ntproceduresfthefieldmeasurementofsoilresistivitybothinsitufsamplesremovedfromthegroundfuseinthecontrolofcrosionofburiedstructures.1.2Toconvertcm(metricunit)tometre(SIunit)divideby100.1.3Thisstarddoesnotpurpttoaddressall

4、ofthesafetyconcernsifanyassociatedwithitsuse.Itistheresponsibilityoftheuserofthisstardtoestablishappropriatesafetyhealthpracticesdeterminetheapplicabilityofregulatylimitationspritouse.2.Terminology2.1Definitions:2.1.1res

5、istivity—theelectricalresistancebetweenoppositefacesofaunitcubeofmaterialthereciprocalofconductivity.Resistivityisusedinpreferencetoconductivityasanexpressionoftheelectricalacterofsoils(waters)sinceitisexpressedinwholenu

6、mbers.2.1.1.1Discussion—Resistivitymeasurementsindicatetherelativeabilityofamediumtocarryelectricalcurrents.Whenametallicstructureisimmersedinaconductivemediumtheabilityofthemediumtocarrycurrentwillinfluencethemagnitudeo

7、fgalvaniccurrentscathodicprotectioncurrents.Thedegreeofelectrodepolarizationwillalsoaffectthesizeofsuchcurrents.3.SummaryofTestMethod3.1TheWennerfourelectrodemethodrequiresthatfourmetalelectrodesbeplacedwithequalseparati

8、oninastraightlineinthesurfaceofthesoiltoadepthnotexceeding5%oftheminimumseparationoftheelectrodes.Theelectrodeseparationshouldbeedwithconsiderationofthesoilstrataofinterest.Theresultingresistivitymeasurementrepresentsthe

9、averageresistivityofahemisphereofsoilofaradiusequaltotheelectrodeseparation.3.2Avoltageisimpressedbetweentheouterelectrodescausingcurrenttoflowthevoltagebetweentheinnerelectrodesismeasuredusingasensitivevoltmeter.Alterna

10、tivelytheresistancecanbemeasureddirectly.Theresistivityristhen:rVcm52paR~aincm!(1)5191.5aR~ainft!where:a=electrodeseparationR=resistanceV.Usingdimensionalanalysisthecrectunitfresistivityisohmcentimetre.3.3Ifthecurrentcar

11、rying(outside)electrodesarenotspacedatthesameintervalasthepotentialmeasuring(inside)electrodestheresistivityris:rVcm595.76bRS12bb1aD(2)where:b=outerelectrodespacingfta=innerelectrodespacingftR=resistanceV.:rVcm5pbRS12bb1

12、aD(3)where:b=outerelectrodespacingcma=innerelectrodespacingcmR=resistanceV.3.4FsoilcontainedinasoilboxsimilartotheoneshowninFig.1theresistivityris:rVcm5RAa(4)where:R=resistanceV1ThistestmethodisunderthejurisdictionofASTM

13、CommitteeG01onCrosionofMetalsisthedirectresponsibilityofSubcommitteeG01.10onCrosioninSoils.CurrenteditionapprovedMay12012.PublishedJune2012.iginallyapprovedin1978.Lastpreviouseditionapprovedin2006asG57–06.DOI:10.1520G005

14、706R12.Copyright?ASTMInternational100BarrHarbDrivePOBoxC700WestConshohockenPA194282959.UnitedStates1where:b=outerelectrodespacingfta=innerelectrodespacingftR=resistanceV.:rVcm5pbRS12bb1aD(6)where:b=outerelectrodespacingc

15、ma=innerelectrodespacingcmR=resistanceV.5.2.3Thedimensionsoftheboxcanbeestablishedsothatresistivityisreaddirectlyfromthevoltmeterwithoutfurthercalculation.Theboxshouldbereadilycleanabletoavoidcontaminationbyprevioussampl

16、es.6.Stardization6.1Periodicallychecktheaccuracyofresistancemetersusingacommercialresistancedecadebox.Metererrshouldnotexceed5%overtherangeoftheinstrument.Iferrexceedsthislimitprepareacalibrationcurvecrectallmeasurements

17、accdingly.Asoilboxcanbecalibratedusingsolutionsofknownresistivity.Solutionsofsodiumchlidedistilledwaterwithresistivitiesof1000500010000Vcmarerecommendedfthispurpose.Thesesolutionsshouldbepreparedunderlabatyconditionsusin

18、gacommercialconductivitymeteritselfcalibratedtostardsolutionsat20C(68F).27.FieldProcedures7.1AtGradeMeasurements:7.1.1thealignmentofthemeasurementtoincludeunifmtopographyoverthelimitsoftheelectrodespan.Donotincludelargen

19、onconductivebodiessuchasfrozensoilbouldersconcretefoundationssofthwhicharenotrepresentativeofthesoilofinterestintheelectrodespan.Conductivestructuressuchaspipescablesshouldnotbewithin1?2aoftheelectrodespanunlesstheyareat

20、rightanglestothespan.7.1.2electrodespacingswithregardtothestructureofinterest.Sincemostpipelinesareinstalledatdepthsoffrom1.5to4.5m(5to15ft)electrodespacingsof1.53.04.5m(51015ft)arecommonlyused.Theaspacingshouldequalthem

21、aximumdepthofinterest.Tofacilitatefieldcalculationofresistivitiesspacingsof1.583.164.75m(5.210.415.6ft)whichresultinmultiplicationfactsof100020003000canbeusedwhenadcvibratgalvanometerinstrumentisused.7.1.3Impressavoltage

22、acrosstheouterelectrodes.Measurethevoltageacrosstheinnerelectrodesrecdboththecurrentvoltageifaseparateammetervoltmeterareused.Wherearesistivitymeterisusedreadtheresistancedirectlyrecd.7.1.4Makearecdofelectrodespacingresi

23、stanceamperesvoltsdatetimeairtemperaturetopographydrainageindicationsofcontaminationtofacilitatesubsequentinterpretation.7.2SoilSampleMeasurement:7.2.1Soilsamplesshouldberepresentativeoftheareaofinterestwherethestratumof

24、interestcontainsavarietyofsoiltypes.Itisdesirabletosampleeachtypeseparately.Itwillalsobenecessarytoprepareamixedsample.Thesampleshouldbereasonablylargethoughlymixedsothatitwillberepresentative.Thesoilshouldbewellcompacte

25、dinlayersinthesoilboxwithairspaceseliminatedasfaraspracticable.Filltheboxflushtothetoptakemeasurementsaspreviouslydetailed(7.1.3).Themeterusedmaylimittheupper2HbookofChemistryPhysics41sted.TheChemicalRubberCo.p.2606.FIG.