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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In the v57 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. Where regular surveys are to be made at? When a metallic structure is immersed in a conductive medium, the ability of the medium to carry current will in?
Last previous edition G 57 — Using dimensional analysis, the correct unit for resistivity is ohm-centimetre. Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm. A soil box can be calibrated using solutions of known resistivity.
Alternatively, the resistance can be measured directly. In the case of soil resistivity measurements reproducibility may be characterized by a coefficient of variation, Cv, representing the reproducibility standard deviation divided by the average result and expressed in percent. A number in parentheses indicates the year of last reapproval.
Triplicate soil resistivity measurements by seven participants each using different meters. Measure the voltage drop across the inner electrodes and record both the current and voltage drop if a separate ammeter and voltmeter are used. If samples are retained for subsequent measurement, correct the resistivity if the measurement temperature is substantially different from the ground temperature.
Surface contamination tends to concentrate in existing ditches with surface run-off, appreciably lowering the resistivity below the natural level. Conductive structures such as pipes and cables should not be within 1? The current can be provided by either a cranked ac generator or a vibrator-equipped dc source.
Where resistivity information is included in published information, the measurement techniques used should be de? The electrodes should be formed with a handle and a FIG. The multiparticipant test program results indicate a reproducibility Cv of Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters.
ASTM G57 Standard
A summary of these data is given g5 Table 1. To evaluate f57 effects when a new route is being evaluated, soil samples can be obtained at crossings of existing pipelines, cables, etc, or by intentional sampling using soil augers. The former method is suited to graphical presentation and plotting resistivity versus distance, and will identify gradients and abrupt changes in soil condition. Since the number of soil sections that could be inspected is essentially unlimited, in?
The multi-participant test program results indicate a repeatability Cv of 6. The electrode separation should be selected with consideration of the soil strata of interest. Where mean or median values cannot be estimated with reasonable accuracy, sequential sampling techniques can be employed. Current edition approved April 15, V57 pedological data should be used to facilitate interpretation.
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 box should be readily cleanable to avoid contamination by previous samples. The resistivity, r, is then: More precise procedures may be employed in laboratory investigations and these should be de? The a spacing should equal the maximum depth of interest. Planning and Interpretation aetm. Precision and Bias 9. Some soils absorb moisture slowly and contain constituents that dissolve slowly, and the resistivity may not stabilize for as much as 24 h after saturation.
The v57 resistivity measurement represents the average resistivity of a hemisphere of soil of a radius equal to the electrode separation. Sharp changes in resistivity with distance and appreciable variations in moisture content and drainage are indicative of local severe conditions. Terminals should be of good quality to ensure that lowresistance contact is made at the electrodes and at the meter. 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 soil should be well-compacted in layers in the soil box, with air spaces eliminated as far as practicable.
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It will also be necessary to prepare a mixed sample. In either case, use pedological surveys in the planning and interpretation of any extensive survey.
Both materials may require heat treatment so that they are sufficiently rigid to be inserted in dry or gravel soils. 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. A nomograph for this correction is shown in Fig.
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Surplus water should not be poured off as this will remove soluble constituents. 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. The effect of variations in compaction and moisture content can be reduced by fully saturating the sample before placing it in the box.