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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Using dimensional analysis, the correct unit for resistivity is h57. Where available, use ground water from the sample excavation for saturation. The former method is suited to graphical presentation and plotting resistivity versus distance, and will identify gradients and abrupt changes in soil condition.
Wstm superscript epsilon e indicates an editorial change since the last revision or reapproval. 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 sample should be reasonably large and thoroughly mixed so that it will be representative.
Sharp changes in resistivity with distance and appreciable variations in moisture content and drainage are indicative of local severe conditions. 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. 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.
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 mean and median resistivity values will indicate the general corrosivity of the soil. Since a pipeline ditch cannot be included in the span of at-grade measurements, soil box samples should be obtained where the opportunity exists.
If samples are retained for subsequent measurement, correct the resistivity if the measurement temperature is substantially different from the ground temperature. When a metallic structure is immersed in a conductive medium, the ability of the medium to carry current will in? Originally published as G 57 — More precise procedures may be employed asstm laboratory investigations and these should be de?
Where mean or median values cannot be estimated with reasonable accuracy, sequential sampling techniques can be employed. The multi-participant test program results indicate a repeatability Cv of 6.
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.
To evaluate contamination 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. A galvanometer type of movement is preferred but an electronic type instrument will yield ast, results if the meter input impedance is at least 10 megaohm. A summary of these data is given in Table 1.
The data from this evaluation are available from ASTM in a research report.
Aztm 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.
Since most pipelines are installed at depths qstm from 1. The soil should be well-compacted in layers in the soil box, with air spaces eliminated as far as practicable. 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 nomograph for this correction is shown in Fig. Otherwise, use distilled water. Surface contamination tends to concentrate in existing ditches with surface run-off, appreciably lowering the resistivity below the natural level.
The effect of variations in compaction and moisture content can be reduced by fully saturating the sample before placing it in the box. The meter used may limit the upper range of resistivity, which can be measured. 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.
Last previous edition G 57 — 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. Surplus water should not be poured off as this will remove soluble constituents.
Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. 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?
Triplicate soil resistivity measurements by seven participants each using different meters. Precision and Bias 9. It is desirable to sample each type separately. Terminals should be of good quality to ensure that lowresistance contact is made at the electrodes and at the meter.
Summary of Test Method 3. 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. Measure the voltage drop across the inner electrodes sstm record both the current and voltage drop if a separate ammeter and voltmeter are used.
Where a resistivity meter is used, read the resistance directly and record. 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 soil box can be calibrated using solutions of known resistivity. Alternatively, the resistance can be measured directly. The multiparticipant test program results indicate a reproducibility Cv of It will also be necessary to prepare a mixed sample.
Both aastm may require heat treatment so that they are sufficiently rigid to be inserted in dry or gravel soils.