1、Designation: G 187 05Standard Test Method forMeasurement of Soil Resistivity Using the Two-ElectrodeSoil Box Method1This standard is issued under the fixed designation G 187; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the equipment and a procedurefor the measurement of soil resistivity, for samples removed
3、from the ground, for use in the control of corrosion of buriedstructures.1.2 Procedures allow for this test method to be used n thefield or in the laboratory.1.3 The test method procedures are for the resistivitymeasurement of soil samples in the saturated condition and inthe as-received condition.1
4、.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly. Soil resistivity values are reported in ohm-centimeter.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespo
5、nsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2G15 Terminology Relating to Corrosion and CorrosionTestingG57 Test Method for Field Measure
6、ment of Soil ResistivityUsing the Wenner Four-Electrode MethodD 1193 Specification for Reagent WaterE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 AISI Specifications:3AISI Designation Type 304AISI Designation Type 3163. Terminology3.1 Definition
7、s:3.1.1 Ohms lawThe relationship between the electromo-tive force, the current, and the resistance. Mathematically:current = electromotive force/resistance or I = E/R; where “I”is measured in amperes, “E” in volts, and “R” in ohms.3.1.2 Resistivity (soil)The electrical resistance betweenopposite fac
8、es of a unit cube of material; the reciprocal ofconductivity.3.1.3 Saturated soilsoil whose entire soil porosity is filledwith water.3.1.4 Soil box factorA factor which is determined by atwo-electrode soil boxs internal dimensions (cross sectionalarea/distance between electrode plates). The soil box
9、 factor ismultiplied by the measured resistance of a substance in the soilbox to obtain that substances resistivity.3.1.5 Soil resistance meterAn instrument capable of mea-suring soil resistance.3.1.6 Two-electrode soil boxA non-conductive containerof known internal dimensions with two end plate ele
10、ctrodes formeasuring a substances resistivity.3.2 The terminology used herein, if not specifically definedotherwise, shall be in accordance with Terminology G15.Definitions provided herein and not given in Terminology G15are limited only to this standard.4. Summary of Test Method4.1 The two-electrod
11、e soil box method is predicated onmeasuring the resistance between two opposite faces of a boxcontaining a substance or solution. That resistance measure-ment through the substance being tested is then converted toresistivity based on the conversion formula of Eq 1.4.2 A voltage is impressed between
12、 the two opposite faceelectrodes, causing current to flow, and the voltage dropbetween them is measured. Ohms law reveals the resistance.The resistivity, r, is then:r ohm2cm! 5 AR/d (1)where:A = cross-sectional area, cm2,R = resistance, ohms, and1This test method is under the jurisdiction of ASTM Co
13、mmittee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.10 onCorrosion in Soils.Current edition approved Oct. 1, 2005. Published November 2005.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For
14、Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American Iron and Steel Institute (AISI), 1140 ConnecticutAve., Suite 705, Washington, DC 20036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
15、shohocken, PA 19428-2959, United States.d = distance between electrodes, cm.5. Significance and Use45.1 The resistivity of the surrounding soil environment is afactor in the corrosion of underground structures. High resis-tivity soils are generally not as corrosive as low resistivitysoils. The resis
16、tivity of the soil is one of many factors thatinfluence the service life of a buried structure. Soil resistivitymay affect the material selection and the location of a struc-ture.55.2 Soil resistivity is of particular importance and interest inthe corrosion process because it is basic in the analysi
17、s ofcorrosion problems and the design of corrective measures.5.3 The test method is focused to provide an accurate,expeditious measurement of soil resistivity to assist in thedetermination of a soils corrosive nature. Test Method G57emphasizes an in situ measurement commonly utilized in thedesign of
18、 a buried structures corrosion control (cathodicprotection systems ground bed design, and so forth). Thetwo-electrode soil box method often compliments the four-pin,in situ soil resistivity method.5.4 The saturated soil resistivity determined by this testmethod does not necessarily indicate the mini
19、mum soil resis-tivity6. Apparatus6.1 The equipment required for the measurement of theresistivity of soil samples, either in the field or in thelaboratory, consists of a two-electrode soil box, a soil resis-tance meter, wiring to make the necessary connections and asoil extraction tool with straight
20、edge. A two-electrode soil box,soil resistance meter and its electrical connections are shown inFig. 1.6.2 Two-electrode soil boxTwo-electrode soil boxes canbe constructed in various sizes provided the inside dimensionsare known. Design and construction shall incorporate materialsthat are durable an
21、d machinable. The two end plate electrodesshall be constructed of a clean, polished corrosion-resistantmetal or alloy (that is, AISI Designation Type 304 or 316stainless steel) that will not form a heavy oxide film orotherwise add significant resistance. The body of the box shallbe constructed of a
22、material that is non-conductive and able tomaintain its desired dimensions (polycarbonate plastics). Thebox shall be readily cleanable to avoid contamination byprevious samples.6.3 Soil resistance meterCommercially available soil re-sistance meters are commonly used for measuring soil resis-tivity (
23、Nilsson Model 400 Soil Resistance Meter6or equiva-lent, which utilize a low voltage 97 Hz square wave current).They offer convenience, ease of use, and repeatability. Soilresistance meters yield direct readings in ohms, which aremultiplied by the appropriate factor for the specific two-electrode soi
24、l box. The meter utilized may limit the upper rangeof resistivity, which can be measured. In such cases theresistivity should be reported as greater than the meters upperlimit.6.4 Wiring18 to 22 AWG insulated stranded copper wire.Terminals and connections must be low-resistance.7. Reagents and Mater
25、ials7.1 Distilled or deionized water (Type IV grade as refer-enced in Specification D 1193) to saturate samples.8. Sampling Test Specimens, and Test Units8.1 Generally, collected soil samples that are to be tested inthe laboratory shall be placed in an appropriate sealablecontainer or polyethylene t
26、ype bag. This allows containers tobe identified for location and will facilitate a request foras-received test results.8.2 Soil samples shall be representative of the area ofinterest. Where the stratum of interest contains a variety of soiltypes, it is desirable to sample each type separately.8.3 Th
27、e collected soil sample size is dependent on thevolume of the soil box used.8.4 Soil resistivity measurements shall not be conducted onfrozen or partially frozen soil samples. Soil samples to betested in the laboratory shall be allowed to reach roomtemperature (approximately 20C (68F) prior to the r
28、esistiv-ity measurement. Field measurements shall reflect the soilstemperature during testing. Soil temperatures that are abovefreezing can be corrected for a uniform temperature of 15.5C(60F) by use of the following equation7:R15.55 Rt24.5 1 t!/ 40 (2)Where R15.5is the resistance at 15.5C (60F) and
29、 Rtis theobserved resistance at temperature tC.9. Calibration and Standardization9.1 The accuracy of the soil resistance meter shall beperiodically checked with a commercial resistance decade boxor several appropriate known value resistors. Meter error shallnot exceed 5 % over the range of the instr
30、ument. If errorexceeds this limit, prepare a calibration curve and correct allmeasurements accordingly.9.2 The two-electrode soil box can be calibrated usingsolutions of known resistivity. Commercially available solu-tions (VWR Conductivity Calibration Standards8) in the rangeof 1000, 5000, and 10,0
31、00 ohm-cm are recommended for thispurpose. Calibration checks are generally performed bi-annually.4Method of Test for the Resistivity of Soils Material, Texas State Department ofHighways and Public Transportation Materials and Tests Division, Test MethodTex-129-E, November 1986.5Method for Estimatin
32、g the Service Life of Steel Culverts, California StateDepartment of Transportation Engineering Service Center, California Test 643,November 1999.6The sole source of supply of the apparatus known to the committee at this timeis Nilsson Electrical Laboratory, 333 West Side Ave., Jersey City, N.J. 0730
33、5, USA.If you are aware of alternative suppliers, please provide this information to ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.7R.O.E. Davis, The use of the electrolytic bridge for determi
34、ning soluble salts.U. S. Dept. Agriculture Circular 423 (1927)8The sole source of supply of the apparatus known to the committee at this timeis VWR International, 1310 Goshen Parkway, West Chester, PA 19380, USA. If youare aware of alternative suppliers, please provide this information to ASTMIntern
35、ational Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.G18705210. Procedure10.1 Procure enough soil sample for testing to accommo-date the soil box.10.2 Examine the sample for the presence of foreign mate-rial s
36、uch as gravel, small stones, roots, twigs, and so forth,which shall be removed from the sample.10.3 Fill the soil box by adding increments of soil. Mixdistilled or deionized water into each soil increment to saturateand help the ionic components of the soil go into solution. Donot over saturate the
37、soil. Compact each wetted soil incrementas densely as possible by hand. Make certain that voids areeliminated. Continue this filling procedure until soil box isslightly over full. Using the straightedge portion of the soilextraction tool, level off the excess hand compacted soil so thesoil conforms
38、to the total volume of the soil box. Add a slightamount more of distilled or deionized water to assure the handcompacted sample is saturated but not over saturated (thepresence of a moisture sheen on top of the sample is desirable).This procedure will allow for a resistivity measurement of thesoil i
39、n a saturated condition.NOTE 1Other soil box resistivity measurement techniques and equip-ment are available. More detailed procedures related to the addition ofwater and compaction of the soil may be employed in controlledlaboratory investigations which should be defined in reporting the results.Wh
40、ere resistivity information is included in published information, themeasurement techniques used should be defined.10.4 Connect the soil resistance meter to the soil box asshown in Fig. 1 and record the resistance measurement.Multiply the resistance measurement value by the appropriatesoil box facto
41、r to obtain the soil resistivity.10.5 When requested to supply as-received sample results,perform the same procedures of steps 10.1-10.4 but eliminatethe addition of water.10.6 The soil resistance measurement using the two-electrode soil box will include the soil resistance between thetwo electrodes
42、 and the interface resistance between the soilsample and the electrode. Tests and experience has shown thatthis interface resistance is negligible.11. Calculation or Interpretation of Results11.1 Each individual soil box will have a unique factordependent upon the internal dimensions of the box. Exa
43、mple:Asoil box with inside dimensions of 4 cm 3 4cm3 4 cm willhave a soil box factor of 4:r5AR/d (3)r54 cm 4cm R/4cmr54R ohmcm!where:FIG. 1 Typical Connections for Use of Soil Box with Soil Resistance MeterG187053A = cross sectional area, cm2,R = resistance, ohm, andd = distance between electrode pl
44、ates, cm.12. Report12.1 Report the following information:12.1.1 Resistivity value for the respective soil samples inohmcm.12.1.2 Temperature of soil sample during measurement.12.1.3 Date when soil sample collected, when sample wastested, depth of sample, location specifics and any otherinformation t
45、hat may facilitate the subsequent interpretation.13. Precision and Bias13.1 PrecisionThe precision of this test method wasdetermined by a statistical evaluation of an interlaboratorystudy per Practice E 691. The data from this evaluation areavailable from ASTM in a research report.9A summary ofthese
46、 data is given in Table 1.13.1.1 RepeatabilityRepeatability refers to the variationin results obtained by the same operator with the sameequipment and the same operating conditions in successivetests. In the case of soil resistivity measurements, the repeat-ability may be characterized by a coeffici
47、ent of variation,CV%r, representing the repeatability standard deviation di-vided by the average result and expressed in percent. The ILSresults indicate a repeatability coefficient of variation of 6.6 %.The 95 % confidence interval is 2.8(CV%r) or 18.5 %.13.1.2 ReproducibilityReproducibility refers
48、 to the varia-tion in results that occurs when different operators measure thesame soil. In the case of soil resistivity measurements repro-ducibility may be characterized by a coefficient of variation,CV%R, representing the reproducibility standard deviationdivided by the average result and express
49、ed in percent. The ILSresults indicate a reproducibility coefficient of variation of10.6 %. The 95 % confidence interval is 2.8(CV%R) or 29.7 %.13.2 BiasThe procedure in this test method for the mea-surement of soil resistivity using the two-electrode soil box hasno bias because the value of the two-electrode soil box soilresistivity is defined only in terms of this test method.14. Keywords14.1 soil box factor; soil resistivity; two-electrode soil boxASTM International takes no position respecting the validity of any patent rights asserted in
