ASTM G57-95A

Standard Test Method for Field Measurement of Soil Resistivity Using the Wenner Four-Electrode Method

SCOPE
1.1 This method covers the equipment and procedures for the field measurement of soil resistivity, both in situand for samples removed from the ground, for use in the control of corrosion of buried structures.
1.2 To convert cm (metric unit) to metre (SI unit), divide by 100.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Dec-2000
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.10 - Corrosion in Soils

Relations

• Replaced By: ASTM G57-95a(2001) - Standard Test Method for Field Measurement of Soil Resistivity Using the Wenner Four-Electrode Method
• Effective Date: 01-Jan-2001
• Referred By: ASTM G200-20 - Standard Test Method for Measurement of Oxidation-Reduction Potential (ORP) of Soil
• Effective Date: 01-Jan-2001
• Referred By: ASTM D420-18 - Standard Guide for Site Characterization for Engineering Design and Construction Purposes
• Effective Date: 01-Jan-2001
• Referred By: ASTM E2277-14(2019) - Standard Guide for Design and Construction of Coal Ash Structural Fills
• Effective Date: 01-Jan-2001
• Referred By: ASTM G218-19 - Standard Guide for External Corrosion Protection of Ductile Iron Pipe Utilizing Polyethylene Encasement Supplemented by Cathodic Protection
• Effective Date: 01-Jan-2001
• Referred By: ASTM D6431-18 - Standard Guide for Using the Direct Current Resistivity Method for Subsurface Site Characterization
• Effective Date: 01-Jan-2001
• Referred By: ASTM G51-18 - Standard Test Method for Measuring pH of Soil for Use in Corrosion Testing
• Effective Date: 01-Jan-2001
• Referred By: ASTM G158-98(2021) - Standard Guide for Three Methods of Assessing Buried Steel Tanks
• Effective Date: 01-Jan-2001
• Referred By: ASTM G187-18 - Standard Test Method for Measurement of Soil Resistivity Using the Two-Electrode Soil Box Method
• Effective Date: 01-Jan-2001
• Referred By: ASTM D6429-23 - Standard Guide for Selecting Surface Geophysical Methods
• Effective Date: 01-Jan-2001
• Referred By: ASTM G162-18 - Standard Practice for Conducting and Evaluating Laboratory Corrosion Tests in Soils
• Effective Date: 01-Jan-2001

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: G 57 – 95a
Standard Test Method for
Field Measurement of Soil Resistivity Using the Wenner
1
Four-Electrode Method
This standard is issued under the fixed designation G 57; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope electrodes is measured using a sensitive voltmeter. Alterna-
tively, the resistance can be measured directly. The resistivity,
1.1 This method covers the equipment and procedures for
r, is then:
the field measurement of soil resistivity, both in situ and for
samples removed from the ground, for use in the control of r,V·cm 5 2p aR ~a in cm!
corrosion of buried structures.
5 191.5 aR~a in ft!
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
where:
responsibility of the user of this standard to establish appro-
a 5 electrode separation, and
priate safety and health practices and determine the applica-
R 5 resistance, V.
bility of regulatory limitations prior to use.
Using dimensional analysis, the correct unit for resistivity is
1.3 To convert cm (metric unit) to metre (SI unit), divide by
ohm-centimetre.
100.
3.3 If the current-carrying (outside) electrodes are not
spaced at the same interval as the potential-measuring (inside)
2. Terminology
electrodes, the resistivity, r is:
2.1 Definition:
b
2.1.1 resistivity—the electrical resistance between opposite
r, V·cm 5 95.76 bR/ 1 2
S D
b 1 a
faces of a unit cube of material; the reciprocal of conductivity.
Resistivity is used in preference to conductivity as an expres-
where:
sion of the electrical character of soils (and waters) since it is
b 5 outer electrode spacing, ft,
expressed in whole numbers.
a 5 inner electrode spacing, ft, and
2.1.2 Resistivity measurements indicate the relative ability
R 5 resistance, V.
of a medium to carry electrical currents. When a metallic or:
structure is immersed in a conductive medium, the ability of
b
r, V·cm5p bR/ 1 2
the medium to carry current will influence the magnitude of S D
b 1 a
galvanic currents and cathodic protection currents. The degree
where:
of electrode polarization will also affect the size of such
b 5 outer electrode spacing, cm,
currents.
a 5 inner electrode spacing, cm, and
3. Summary of Test Method
R 5 resistance, V.
3.4 For soil contained in a soil box similar to the one shown
3.1 The Wenner four-electrode method requires that four
in Fig. 1, the resistivity, r, is:
metal electrodes be placed with equal separation in a straight
line in the surface of the soil to a depth not exceeding 5 % of r, V·cm 5 RA/a
the minimum separation of the electrodes. The electrode
where:
separation should be selected with consideration of the soil
R 5 resistance, V,
strata of interest. The resulting resistivity measurement repre-
A 5 cross sectional area of the container perpendicular to
sents the average resistivity of a hemisphere of soil of a radius
2
the current flow, cm , and
equal to the electrode separation.
a 5 inner electrode spacing, cm.
3.2 A voltage is impressed between the outer electrodes,
causing current to flow, and the voltage drop between the inner NOTE 1—The spacing between the inner electrodes should be measured
from the inner edges of the electrode pins, and not from the center of the
electrodes.
1
This method is under the jurisdiction of ASTM Committee G-1 on Corrosion of
Metals, and is the direct responsibility of Subcommittee G01.10 on Corrosion in
4. Apparatus
Soils.
Current edition approved April 15, 1995. Published June 1995. Originally 4.1 At-Grade Measurements in situ:
published as G 57 – 78. Last previous edition G 57 – 95.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
G57
FIG. 1 Typical Connections for Use of Soil Box with Various Types of Instruments
4.1.1 The equipment required for field resistivity measure- 4.1.3 Voltmeter—The voltmeter shall not draw appreciable
ments to be taken at grade consists of a current source, a current from the circuit to avoid polarization effects. A galva-
suitable voltmeter, ammeter, or galvanometer, four metal nometer type of movement is preferred but an electronic type
electrodes, and the necessary wiring to make the connections instrument will yield satisfactory results if the meter input
shown in Fig. 2. impedance is at least 10 megaohm.
4.1.2 Current Source—An ac source, usually 97 Hz, is 4.1.4 Electrodes fabricated from mild steel or martensitic
3 1
preferred since the use of dc will cause polarization of most stainless steel 0.475 to 0.635
...