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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An unaltered dc source can be used if the electrodes are abraded to bright metal before immersion, polarity is regularly reversed during measurement, and measurements are averaged for each polarity. Where mean or median values cannot be estimated with reasonable accuracy, aatm sampling techniques can be employed. The electrode separation should be selected with consideration of the soil strata of interest.
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A galvanometer type of movement is preferred but an electronic type instrument will yield satisfactory results if the meter input impedance is at least 10 megaohm. Measurements could be made in each soil classi?
The resulting astk measurement represents the average resistivity of a hemisphere of soil of a radius equal to the electrode separation. Measure the voltage drop across the inner electrodes and record both the asttm and voltage drop if a separate ammeter and voltmeter are used.
The a spacing should equal the maximum depth of interest. When a metallic structure is immersed in a conductive medium, the ability of the medium to carry current will in?
Where a resistivity meter is used, read the resistance directly and record. The electrodes should be formed with a handle and a FIG. It will also be necessary to prepare a mixed sample.
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Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. Summary of Test Method 3.
Triplicate soil resistivity measurements by seven participants each using different meters. The data from this evaluation are available from ASTM in a research report. Using dimensional analysis, the correct unit for resistivity is ohm-centimetre.
Available pedological data should be used to facilitate interpretation. Alternatively, the resistance can be measured directly.
Do not include large nonconductive bodies such as frozen soil, boulders, concrete foundations, etc. In the case of soil resistivity measurements, the repeatability may be characterized by a coefficient of variation, Cv, representing the repeatability standard deviation divided by the average result and expressed in percent.
The multi-participant test program results indicate a repeatability Cv of 6. Since a pipeline ditch cannot be included in the span of at-grade measurements, soil box samples should be obtained where the opportunity exists.
The sample should be reasonably large and thoroughly mixed so that it will be representative. Otherwise, use distilled water. It is desirable to sample each type separately.
The two-electrode technique is inherently less accurate astmm the four-electrode method because of polarization effects, but useful information can be obtained concerning the characteristics of particular strata. A nomograph for this correction is shown in Fig. In either case, use pedological surveys in the planning asm interpretation of any extensive survey.
ASTM G57 Standard
Terminals should be of good quality to ensure that g5 contact is made at the electrodes and at the meter. Your comments are invited either for revision of this standard or for additional standards and should be addressed to Asstm Headquarters.
More precise procedures may be employed in laboratory investigations and these should be de? This can be done by preparing a stiff slurry of the sample, adding b57 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.
A superscript epsilon e indicates an editorial change since the last revision or reapproval. Precision and Bias 9. Where resistivity information is included in published information, the measurement techniques used should be 5g7 The effect of variations in compaction and moisture content can be reduced by fully saturating the sample before placing it in the box.
The multiparticipant test program results indicate a reproducibility Cv of The soil should be well-compacted in layers in the soil box, with air spaces eliminated as far as practicable.