1、Designation: G187 18Standard Test Method forMeasurement of Soil Resistivity Using the Two-ElectrodeSoil Box Method1This standard is issued under the fixed designation G187; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the equipment and proceduresfor the measurement of soil resistivity, for soil samplesremoved
3、 from the ground, for use in the assessment and controlof corrosion of buried structures.1.2 Procedures allow for this test method to be used in 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-rec
4、eived condition.1.4 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 us
5、e. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and todetermine the applicability of regulatory limitations prior touse.1.6 This international standard was developed in accor-dance with internationally recognized principle
6、s on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Wate
7、rE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodG57 Test Method for Field Measurement of Soil ResistivityUsing the Wenner Four-Electrode MethodG193 Terminology and Acronyms Relating to Corrosion2.2 UNS Standards:3UNS Designation S30400 the reciprocal
8、of con-ductivity.3.1.3 saturated soil, nsoil whose entire soil porosity isfilled with water.3.1.4 soil box factor, nA factor which is determined by atwo-electrode soil boxs internal dimensions (cross sectionalarea/distance between electrode plates). The soil box factor ismultiplied by the measured r
9、esistance of a substance in the soilbox to obtain that substances resistivity.3.1.5 soil resistance meter, nAn instrument capable ofmeasuring soil resistance.3.1.6 two-electrode soil box, nAnon-conductive containerof known internal dimensions with two end plate electrodes formeasuring a substances r
10、esistivity.3.2 The terminology used herein, if not specifically definedotherwise, shall be in accordance with Terminology G193.Definitions provided herein and not given in TerminologyG193 are limited only to this standard.4. Summary of Test Method4.1 The two-electrode soil box method is predicated o
11、nmeasuring the resistance between two electrodes located onopposing faces of a soil box containing a soil sample. That1This test method is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.10 onCorrosion in Soils.Current edition a
12、pproved May 1, 2018. Published July 2018. Originally approvedin 2005. Last previous edition approved in 2012 as G187 12a. DOI: 10.1520/G0187-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards v
13、olume information, refer to the standards Document Summary page onthe ASTM website.3UNS (Unified Numbering System) was developed jointly by ASTM Interna-tional and SAE International.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis
14、international standard was developed in accordance with internationally recognized 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
15、) Committee.1resistance is then converted to resistivity based on the soil boxfactor as discussed in Section 11.5. 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 corrosiv
16、e as low resistivitysoils. The resistivity 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 proces
17、s because it is basic in the analysis 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 measureme
18、nt commonly utilized in thedesign of a buried structures corrosion control (cathodicprotection systems ground bed design, and so forth), but alsoincludes information and procedures on a four-pin soil boxmethod. The two-electrode soil box method is an accurate andmore expeditious method than the four
19、-pin soil box and oftencompliments the four-pin, in situ soil resistivity method.5.4 The saturated soil resistivity determined by this testmethod does not necessarily indicate the minimum soil resis-tivity.6. Apparatus6.1 The equipment required for the measurement of theresistivity of soil samples,
20、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 straightedge. A two-electrode soil box,soil resistance meter and its electrical connections are shown inFig. 1.NOTE 1The so
21、il extraction tool should be non-metallic so as to avoiddamage to the soil box during use. It should fit within the soil box tofacilitate removal of the soil sample after completion of each test. Itshould be rigid enough to aid in compaction of the soil sample in the soilbox, and it should have a st
22、raight edge to facilitate levelling of the soilsample after compaction. The soil extraction tool may be a commerciallyavailable utensil designed specifically for use with the soil box. In lieu ofthis, any suitable implement such as a plastic putty knife may be used.6.2 Two-Electrode Soil BoxTwo-elec
23、trode soil boxes canbe constructed in various sizes provided the inside dimensionsare known. Design and construction shall incorporate materialsthat are durable and machinable. The two end plate electrodesshall be constructed of a clean, polished corrosion-resistantmetal or alloy (that is, UNS Desig
24、nation type S30400/S304034Method 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 Estimating the Service Life of Steel Culverts, California StateDepartment of Trans
25、portation Engineering Service Center, California Test 643,November 1999.FIG. 1 Typical Connections for Use of Soil Box with Soil Resistance MeterG187 182or UNS S31600/S31603 stainless steel) that will not form aheavy oxide film or otherwise add significant resistance. Thebody of the box shall be con
26、structed of a material that isnon-conductive and able to maintain its desired dimensions(polycarbonate plastics). The box shall be readily cleanable toavoid contamination by previous samples. See Fig. 2.6.3 Four Terminal Resistance MeterCommercially avail-able four terminal soil resistance meters ar
27、e commonly used formeasuring soil resistivity. They offer convenience, ease of use,and repeatability. Soil resistance meters yield direct readings inohms, which are multiplied by the appropriate factor for thespecific two-electrode soil box. The meter utilized may limitthe upper range of resistivity
28、, which can be measured. In suchcases, the resistivity should be reported as greater than themeters upper limit.6.4 Wiring18 to 22 AWG insulated stranded copper wire.NOTE 2It is important to make reliable, low-impedance electricalconnections. Ensure that all terminals are clean, and all wiring conne
29、ctionsare made securely.6.5 MiscellaneousDepending on how and where the soilwill be analyzed, one or more of the following may be needed:hand auger, post-hole diggers, sample bags, glass container,soil thermometer, indelible marker, etc.7. Reagents and Materials7.1 Distilled or deionized water (Type
30、 IV grade as refer-enced in Specification D1193) to saturate samples.7.2 Commerically available solutions (VWR ConductivityCalibration Standards6) in the range of 1000, 5000, and 10 000ohm-cm are recommended for this purpose.6The sole source of supply of the apparatus known to the committee at this
31、timeis VWR International, 1310 Goshen Parkway, West Chester, PA 19380, USA. If youare 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
32、attend.FIG. 2 Typical Two-Electrode Soil Box (Empty and Full)G187 1838. Sampling Test Specimens, and Test Units8.1 Soil samples may be brought to the surface using anauger, post hole digger, shovel, etc. or can be collected fromthe sides of an excavated trench. Soil samples shall berepresentative of
33、 the area of interest. Where the stratum ofinterest contains a variety of soil types, it is desirable to sampleeach type separately. Foreign material such as gravel, smallstones, roots, twigs, and so forth shall be avoided duringcollection of the sample.8.2 Collected soil samples that are to be test
34、ed in thelaboratory shall be placed in an appropriate sealable containeror polyethylene type bag to prevent contamination. Eachsample shall be clearly marked with the location, depth,collection date, and sample temperature at the time of collec-tion.NOTE 3The resistivity of a soil sample does not ty
35、pically change overtime. However, it is advisable to conduct your tests typically within a fewweeks after sample collection to avoid any unforeseen changes. It is alsoadvisable to avoid prolonged exposure of samples to extreme heat ordirect sunlight.8.3 The collected soil sample size is dependent on
36、 thevolume of the soil box used. Be sure to collect enough soil toallow for compaction during the test. It is also advisable tocollect extra soil in case repeated testing becomes necessary.9. Calibration and Standardization9.1 The accuracy of the soil resistance meter shall beperiodically checked wi
37、th a commercial resistance decade boxor several appropriate known value resistors. Meter error shallnot exceed 5 % over the range of the instrument. If errorexceeds this limit, the meter should be recalibrated as soon aspossible. Until such time, an alternate calibrated meter may beused or a calibra
38、tion curve can be established and used tocorrect all measurements.9.2 Accuracy of the two-electrode soil box can be verifiedusing solutions of known resistivity. Commercially availablesolutions (VWR Conductivity Calibration Standards6)intherange of 1000, 5000, and 10 000 ohm-cm are recommended forth
39、is purpose. Accuracy checks are generally performed bian-nually.9.3 Soil Box FactorDifferent soil boxes will have differentfactors (that is, multiplier) dependent upon the internal dimen-sions of the box (refer to 11.1).10. Procedure10.1 Collect soil sample in accordance with Section 8.10.2 Examine
40、the sample for the presence of foreign mate-rial such as gravel, small stones, roots, twigs, and so forth,which shall be removed from the sample.10.3 Soil resistivity measurements shall not be conductedon frozen or partially frozen soil samples. Soil samples shall beallowed to reach room temperature
41、 (approximately 20C(68F) prior to the resistivity measurement. Field measure-ments shall note the soils temperature at the time of testing.Resistivity values for test soils with temperatures that areabove freezing can be corrected for a uniform temperature of15.5C (60F) per 11.3.10.4 Fill the soil b
42、ox 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 oversaturate the soil. Compact each wetted soil incrementas densely as possible by hand. Make certain that voids areeliminated. Conti
43、nue 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 to the total volume of the soil box. Add a slightamount more of distilled or deionized water to ensure the handcompa
44、cted sample is saturated but not oversaturated (thepresence of a moisture sheen on top of the sample is desirable).This procedure will allow for a resistivity measurement of thesoil in a saturated condition.NOTE 4Other soil box resistivity measurement techniques and equip-ment are available. More de
45、tailed 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.Where resistivity information is included in published information, themeasurement techniques used should be defined.1
46、0.5 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 factor to obtain the soil resistivity.10.6 When requested to supply as-received sample results,perform the same procedure
47、s of steps 10.1 10.5, but eliminatethe addition of water.10.7 The soil resistance measurement using the two-electrode soil box will include the soil resistance between thetwo electrodes and the interface resistance between the soilsample and the electrode. Tests and experience has shown thatthis int
48、erface resistance is negligible.11. Calculation or Interpretation of Results11.1 A soil box will have a soil box factor based on itsinternal dimensions and the exposed area of the electrodeend-plate. The soil box factor is calculated as follows:Soil Box Factor 5 AD (1)where:A = exposed area of elect
49、rode end-plate, andD = distance between the electrode plates of the soil box.Example: A soil box with an exposed electrode area of 25cm2(each) and a distance of 10 cm between electrodes willhave a soil box factor of 25 /10 = 2.5.11.2 Soil resistivity is calculated based on the measuredresistance and the soil box factor as follows: 5 R*Soil Box Factor (2)where: = resistivity, ohm-cm, andR = measured resistance in ohms.Example: A soil sample is measured and found to have 1000ohms of resistance, in a soil box with a factor of 2.5. Theresistivity wou
