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 mean and median resistivity values will indicate the general corrosivity of the soil.
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Resistivity is used in preference to conductivity as an expression of the electrical character of soils and waters since it is expressed in whole numbers. A superscript epsilon e indicates an editorial change since the last revision or reapproval. The effect of variations in compaction and moisture content can be reduced by fully saturating the sample before placing it in the box. Surplus water should not be poured off as this will remove soluble satm. It is desirable to sample each type separately.
In either case, use pedological surveys in the planning and interpretation of any extensive survey. Terminals should be of good quality to ensure that lowresistance contact is made at the electrodes and at the meter. Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm. The multiparticipant test program results indicate a reproducibility Cv of Both materials may require heat treatment so that they g577 sufficiently rigid to be inserted in dry or gravel soils.
Current edition approved April 15, Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters.
If error exceeds this limit, prepare a calibration curve and correct all measurements accordingly. The current can be provided by either a cranked ac generator or a vibrator-equipped dc source. In the case of soil resistivity measurements, the repeatability may be characterized by a coefficient of variation, Asfm, representing the repeatability standard deviation divided by the average result and expressed in percent. 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.
The sample should be reasonably large and thoroughly mixed so that it will be representative.
A summary of these data is given in Table 1. The box should be readily cleanable to avoid contamination by previous samples. The former method is suited to graphical presentation and plotting resistivity versus distance, and will identify gradients and abrupt changes in soil condition. 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.
The electrodes should be formed with a handle and a FIG. 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. Planning and Interpretation 7. The a spacing should equal the maximum depth of interest. Since a pipeline ditch cannot be included atm the span of at-grade measurements, soil box samples should be obtained where the opportunity exists.
Triplicate soil resistivity measurements by seven participants each using different meters. This standard b57 subject to revision at any time by the responsible technical committee and must be reviewed every? 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. Using dimensional analysis, the correct unit for resistivity is ohm-centimetre.
Alternatively, the resistance can be measured directly. The meter used may limit the upper range of resistivity, which can be measured.
A soil box can be calibrated using solutions of known resistivity. The electrode separation should be selected with consideration of the soil strata of interest. Otherwise, use distilled water. The resistivity, r, is then: 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.
Since most pipelines are installed at depths of from 1. Surface contamination tends to concentrate in existing ditches with surface run-off, appreciably lowering the resistivity below the natural level. Since the number of soil sections that could be inspected is essentially unlimited, in? Conductive structures such as pipes and cables should not be within 1?
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Do not include large nonconductive bodies such as frozen soil, boulders, concrete foundations, etc. 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 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. Risk and error must be arbitrarily selected to allow determination of the number asrm measurements.
ASTM G57 Standard
Measurements could be made in sstm soil classi? Last previous edition G 57 — It will also be necessary to prepare a mixed sample. 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.
The multi-participant test program results indicate a repeatability Cv of 6. Where available, use ground water from the sample excavation for saturation. This can be done by preparing a stiff slurry of the sample, adding only sufficient water to produce a slight amount of surface asrm, which should be allowed to evaporate before the slurry is remixed and placed in the box.