Standard Test Method for Field Measurement of Soil Resistivity Using the Wenner Four-Electrode Method. Soil testing is performed for a variety of reasons, from agricultural to environmental. Find out why the ASTM G57 standard may be helpful for. Geotechnical and power engineers, find out how to perform a fall-of-potential or ASTM G57 test.
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The data from this evaluation are available from ASTM in a research report.
A soil box can be calibrated using solutions of known resistivity. Surplus water should not be poured off as this will remove soluble constituents. A nomograph for this correction is shown in Fig.
The multi-participant test program results indicate a repeatability Cv of 6. Risk and error must be arbitrarily selected to allow determination of the number of measurements.
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.
To evaluate contamination effects when a new route is being evaluated, soil samples can be obtained at crossings y57 existing pipelines, cables, etc, or by intentional sampling using soil augers. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. The meter used may limit the upper range of resistivity, which can be measured. The two-electrode technique is inherently less accurate than the four-electrode method because of polarization effects, but useful information can be obtained concerning the characteristics of particular strata.
Aetm comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters. The current can be provided by either a cranked ac generator or a vibrator-equipped dc source.
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The former method is suited to graphical presentation and plotting resistivity versus distance, and will identify gradients and abrupt changes in soil condition. The sample should be reasonably large and thoroughly mixed so ast it will be representative. The multiparticipant test program results indicate a reproducibility Cv of The a spacing should equal the maximum depth of interest. Some soils absorb moisture slowly and contain constituents that dissolve slowly, and the resistivity may not stabilize for as much ast 24 astmm after saturation.
Since the number of soil sections that could be inspected is essentially unlimited, in? Where a resistivity meter is used, read the resistance directly and record. The electrode separation should be selected with consideration of the soil strata of interest.
This can be done by preparing a stiff slurry of the sample, adding only sufficient water to produce a slight amount of surface water, which should be allowed to evaporate before the slurry is remixed and placed in the box.
It asgm also be necessary to prepare a mixed sample. This method permits the determination of the probability of the presence of a soil with a resistivity equal to or greater than a particular value. The latter method permits precise mathematical treatment, such as cumulative probability analysis.
It is desirable to sample each type separately.
Since a pipeline ditch cannot be included in the span of at-grade measurements, soil box samples should be obtained where the opportunity exists. 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. The resulting resistivity measurement represents the average resistivity of a hemisphere of soil of a radius equal to the electrode separation. Where available, use ground water from the sample excavation for saturation.
A number in parentheses indicates the year of last reapproval. If samples are retained for subsequent measurement, correct the resistivity if the measurement temperature is substantially different from the ground temperature.
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This standard is subject to revision at any time by the responsible technical committee and must be reviewed every? Conductive structures such as pipes and cables should not be within 1? The effect of variations in compaction and moisture content can be reduced by fully saturating the sample before placing it in the box. Summary of Test Method 3. The electrodes should be formed with a handle and a Satm.
The resistivity, r, is then: Where regular surveys are to be made at? Where mean or median values cannot be estimated with reasonable accuracy, sequential sampling techniques can be employed. These commonly use two electrodes mounted on a prod that is inserted in the soil-at-grade in an excavation or a driven or bored hole. Surface contamination y57 to concentrate in existing ditches with surface run-off, appreciably lowering the resistivity below the natural level.