1、This international standard was developed in accordance with internationallygnized principles on standardization established in the Decision on Principles for theDevelopment of International Standards.Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)C
2、ommittee.Designation:G57-20NTERNATIONALStandard Test Method forMeasurement of Soil Resistivity Using the Wenner Four-Electrode Method1This standard is issued under the fixed designation G57:the number immediately following the designation indicates the year of originaladoption or,in the case of revi
3、sion.the year of last revision.A number in parentheses indicates the year of last reapproval.A superscriptepsilon(e)indicates an editorial change since the last revision or reapproval1.Scope2.2 UNS Standards:31.1 This test method covers the equipment and proceduresUNS Designation S30400 and S30403fo
4、r the measurement of soil resistivity,both in situ and forUNS Designation S31600 and S31603samples removed from the ground,for use in assessment and3.Terminologycontrol of corrosion of buried structures.3.1 Definitions:1.2 The values stated in SI units are to be regarded as3.1.I four-electrode soil
5、box,n-a non-conductive containerstandard.The values given in parentheses after SI units areof known internal dimensions with four electrodes for measur-provided for information only and are not considered standard.ing a substances resistivity.Soil resistivity values are reported in ohm-centimeter.3.
6、1.2 saturated soil,n-soil whose entire soil porosity is1.3 This standard does not purport to address all of thefilled with water.safety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-3.1.3 soil resistance meter,n-an instrument capable
7、ofpriate safety,health,and environmental practices and deter-measuring soil resistance.mine the applicability of regulatory limitations prior to use.3.1.4 soil resistivity,n-the electrical resistance between1.4 This international standard was developed in accor-opposite faces of a unit cube of mater
8、ial,typically expressed indance with internationally recognized principles on standard-ohm-meter,ohm-cm,or similar units;the reciprocal of con-ization established in the Decision on Principles for theductivityDevelopment of International Standards,Guides and Recom-3.2 The terminology used herein,if
9、not specifically definedmendations issued by the World Trade Organization Technicalotherwise,shall be in accordance with Terminology G193.Barriers to Trade(TBT)Committee.Definitions provided herein and not given in Terminology2.Referenced DocumentsG193 are limited only to this test method.2.1 ASTM S
10、tandards:23.3 Discussion-Resistivity measurements indicate the rela-D1193 Specification for Reagent Watertive ability of a medium to carry electrical currents.When ametallic structure is immersed in a conductive medium,theE691 Practice for Conducting an Interlaboratory Study toDetermine the Precisio
11、n of a Test Methodability of the medium to carry current will influence theG187 Test Method for Measurement of Soil Resistivitymagnitude of galvanic currents and cathodic protection cur-Using the Two-Electrode Soil Box Methodrents.The degree of electrode polarization will also affect theG193 Termino
12、logy and Acronyms Relating to Corrosionsize of such currents.4.Summary of Test MethodThis test method is under the jurisdiction of ASTM Committee Gol on4.1 The Wenner four-electrode method requires that fourCorrosion of Metals and is the direct responsibility of Subcommittee G01.10 onmetal electrode
13、s be placed with equal separation in a straightCorrosion in Soils.Current edition approved Nov.1.2020.Published December 2020.Originallyline in the surface of the soil to a depth not exceeding 5 ofapproved in 1978.Last previous edition approved in 2012 as G57-06(2012).DOI:the minimum separation of t
14、he electrodes.The electrode10.1520/G0057-20.2 For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTM3 Metals and Alloys in the Unified Numbering System(UNS).13th Edition.Standards volume information,refer to the st
15、andards Document Summary pageondeveloped jointly by ASTM International,West Conshohocken.PA.and SAEthe ASTM website.Intemational,Warrendale.PA.2017.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesG57-20SOIL BOXMILLIAMMETERMILLIVOLTMETERCR A
16、MMETEROR VOLTMETERSOIL BOXSOfL BOXSOIL BOXC12FIG.1 Typical Connections for Use of Soil Box with Various Types of Instrumentsseparation should be selected with consideration of the soilwhere:strata of interest.The resulting resistivity measurement repre-b outer electrode spacing,ft,sents the average
17、resistivity of a hemisphere of soil of a radiusa=inner electrode spacing,ft,andequal to the electrode separation.R=resistance,.4.2 A voltage is impressed between the outer electrodes,or:causing current to flow,and the voltage drop between the innerp,2cm=bR(1+b/a）(3)electrodes is measured using a vol
18、tmeter.Alternatively,theresistance can be measured directly using a soil resistancewhere:meter.The resistivity,p,is then:b outer electrode spacing,cm,a inner electrode spacing,cm,andp.n.cm 2x aR(a in cm)(1)R=resistance,=191.5 aR(a in ft)4.4 For soil contained in a soil box similar to the one shownin
19、 Fig.1,the resistivity,p,is:where:a electrode separation,andp.9.cm=R A/a(4)R=resistance,Q.where:Using dimensional analysis,the correct unit for resistivity isR resistance,ohm-centimeter.A cross sectional area of the container perpendicular to thecurrent flow.cm-,and4.3 If the current-carrying(outsid
20、e)electrodes are nota inner electrode spacing,cm.spaced at the same interval as the potential-measuring(inside)electrodes,the resistivity,p.is:NorE 1-The spacing between the inner electrodes should be measuredfrom the inner edges of the electrode pins,and not from the center of thep,2-cm=95.76bR(1+b
21、/a)(2)electrodes.G57-20the box shall be constructed of a material that is non-multiplication factors of 1000,2000,and 3000,can be usedconductive and able to maintain its desired dimensions(poly-when a d-c vibrator-galvanometer instrument is used.carbonate plastics).The box shall be readily cleanable
22、 to avoid9.1.3 Impress a voltage to create a current across the outercontamination by previous samples.Some soil box designselectrodes.Measure the voltage drop across the inner elec-incorporate removable pins(that is,electrodes)to facilitatetrodes and record both the current and voltage drop if acle
23、aning.Other soil box designs incorporate two electrodes inseparate ammeter and voltmeter are used.Where a resistivitylieu of four electrodes(see Test Method G187).meter is used,read the resistance directly and record6.2.3 If the current-carrying(outside)electrodes are notspaced at the same interval
24、as the potential-measuring(inside)NorE 2-Some newer models of soil resistivity meters allow resistivityelectrodes,the resistivity,p,is determined using Eq 2,wheremeasurements to be collected in such a way as to automatically analyzesoil resistivity at different depths.A number of pins are driven at
25、equalthe spacing is given in feet,and Eq 3,where the electrodespacing and the instrument switches between different combinations ofspacing is given in centimeters.four pins.The information can then be processed using software to give6.2.4 The dimensions of the box can be established so thateither on
26、e or two dimensional profilesresistivity is read directly from the voltmeter without further9.1.4 Make a record of electrode spacing.resistance orcalculation.The box should be readily cleanable to avoidamperes and volts,date,time,ambient temperature,contamination by previous samples.topography,drain
27、age,and indications of contamination tofacilitate subsequent interpretation.7.Reagents and Materials7.1 Distilled or deionized water(Type IV grade as refer-9.2 Soil Sample Measurement(that is,soil box measure-enced in Specification D1193)to saturate samples.ments):9.2.1 Soil samples should be repres
28、entative of the area of7.2 Commercially available solutions in the range ofinterest where the stratum of interest contains a variety of soil1000 ohm-cm,5000 ohm-cm,and 10 000 ohm-cm are recom-types.It is desirable to sample each type separately.It will alsomended for the purpose of calibration.be ne
29、cessary to prepare a mixed sample.The sample should be8.Standardizationreasonably large and thoroughly mixed so that it will berepresentative.The mixed soil should be well-compacted in8.1 Periodically check the accuracy of resistance meterslayers in the soil box,with air spaces eliminated as far asu
30、sing manufacturers recommendations.Meter error should notpracticable.Fill the box flush to the top and take measurementsexceed 5 over the range of the instrument.If error exceedsas previously detailed(9.1.3).The meter used may limit thethis limit,prepare a calibration curve and correct all measure-u
31、pper range of resistivity,which can be measured.In suchments accordingly.A soil box can be calibrated using solutionscases,the resistivity should be recorded as 10 000.cm.andof known resistivity.Solutions of sodium chloride and distilledso forth.water with resistivities of 1000.cm.5000.cm,and9.2.2 T
32、he measured resistivity will be dependent on the10 000.cm are recommended for this purpose.These solu-degree of compaction,moisture content,constituent solubility,tions should be prepared under laboratory conditions using aand temperature.The effect of variations in compaction andcommercial conducti
33、vity meter,itself calibrated to standardmoisture content can be reduced by fully saturating the samplesolutions at 20C(68 F).4before placing it in the box.This can be done by preparing astiff slurry of the sample,adding only sufficient water to9.Field Proceduresproduce a slight amount of surface wat
34、er.which should be9.1 At-Grade Measurements:allowed to evaporate before the slurry is remixed and placed in9.1.1 Select the alignment of the measurement to includethe box.Where available,use ground water from the sampleuniform topography over the limits of the electrode span.Doexcavation for saturat
35、ion.Otherwise,use ASTM Specificationnot include large nonconductive bodies such as frozen soil,D1193 reagent water.If the soil resistivity is expected to beboulders,concrete foundations,and so forth,which are notbelow 10000 1.cm,local tap water can be used withoutrepresentative of the soil of intere
36、st,in the electrode span.introducing serious error.Conductive structures such as pipes and cables should not bewithin 2 a of the electrode span unless they are at right anglesNore 3-Some soils absorb moisture slowly and contain constituentsthat dissolve slowly,and the resistivity may not stabilize f
37、or as much as 24to the span.h after saturation.9.1.2 Select electrode spacings with regard to the structureof interest.Since most pipelines are installed at depths of fromThe saturated measurement will provide an approaching1.5 m to 4.5 m(5 ft to 15 ft).electrode spacings of 1.5 m,minimum resistivit
38、y,and can be usefully compared with3.0 m,and 4.5 m(5 ft,10 ft,and 15 ft)are commonly used.Theas-receivedresistivity measurements.Surplus water shoulda spacing should equal the maximum depth of interest.Tonot be poured off as this will remove soluble constituents.facilitate field calculation of resis
39、tivities,spacings of 1.58 m,9.2.3 Temperature-Soils shall not be frozen at the time of3.16 m,and 4.75 m(5.2 ft,10.4 ft,and 15.6 ft),which result inmeasurement.Temperature correction will not be required ifmeasurement is made in-the-ditch or immediately after thesample is taken.If samples are retaine
40、d for subsequentHandbook of Chemistry and Physics,41st ed.,The Chemical Rubber Co.,p.measurement,correct the resistivity if the measurement tem-2606.perature is substantially different from the ground temperature.Copyright ASTM IntemationalG57-2030EXAMPLE:GIVEN OBSERVED VALUES OF 80 OHMSAND 56F(13.3
41、C).CONNECT THESE POINTS ON THEOUTER SCALES WITH A STRAIGHT EDGE OR FINEBLACK THREAD.THE LINE INTERSECTS THE SCALEFOR OHMS AT 60F(15.6C).AT 75 OHMS5040FIG.3 Nomogram or Conversion Chart for Reducing Soil Paste Resistance in ohms at a Particular Temperature as Measured in theBureau of Soils Cup,to Res
42、istance at 15.6C(60F)Correction to 15.5 C(60F)is recommended if the samplethe determination of the probability of the presence of a soiltemperature exceeds 21 C(70 F).with a resistivity equal to or greater than a particular value.24.5+TWhere random resistivities are measured over a plant site.RI5s=R
43、T40(5)these can best be displayed on a plot plan or similar layout.Ineither case,use pedological surveys in the planning andwhere:interpretation of any extensive survey.Measurements could beTsoil temperature,C,andmade in each soil classification under a variety of drainageR=resistivity at T C.condit
44、ions to simplify survey planning.A nomograph for this correction is shown in Fig.3.310.1.2 If the random interval(that is,statistical)method isutilized to assess the requirement for corrosion control10.Planning and Interpretationmeasures,it is recommended that the tests be made on a true10.1 Plannin
45、g:random basis.Since the number of soil sections that could be10.1.1 Surveys may be conducted at regular or randominspected is essentially unlimited,infinite population charac-intervals.The former method is suited to graphical presentationteristics can be used to simplify statistical treatment.Risk
46、andand plotting resistivity versus distance and will identify gradi-error must be arbitrarily selected to allow determination of theents and abrupt changes in soil condition.In addition to regularnumber of measurements.A risk of 5%of an error greater thanintervals,resistivity measurements should be
47、conducted at any100 R-cm should be suitable for most situations.The error limitareas with geographical changes,which may result in abnor-should be about 10%of the anticipated mean resistivity.mally high or low soil resistivities.The latter random intervalWhere mean or median values cannot be estimat
48、ed withmethod permits precise mathematical statistical treatment,suchreasonable accuracy,sequential sampling techniques can beas cumulative probability analysis.This test method permitsemployed.Scout.G.N.Corrosion,National Association of Corrosion Engineers,Vols National Institute of Standards and Technology Circular No.579,p.157.14.No.8.August 1958.5
