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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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. The current can be provided by either a cranked ac generator or a vibrator-equipped dc source.
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Resistivity is used in preference to conductivity as an expression of the electrical character of adtm and waters since it is expressed in whole numbers. The electrodes should be formed with a handle and a FIG.
Where available, use ground water from the sample excavation for saturation. The latter method permits precise mathematical treatment, such as atm probability analysis. Last previous edition G 57 — The former method is suited to graphical presentation and plotting resistivity versus distance, and will identify gradients and abrupt changes in soil condition.
Since most pipelines are installed at depths of from 1.
It will also be necessary to prepare a mixed sample. Where a resistivity meter is used, read the resistance directly and record.
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 effect of variations in compaction and moisture content can be reduced by fully saturating the sample before placing it in the box.
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 number in parentheses indicates the year of last reapproval. A summary of these data is given in Table 1. A nomograph for this correction is shown in Fig.
ASTM G57 Standard
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. 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.
A superscript epsilon e indicates an editorial change since the last revision or reapproval. Otherwise, use distilled water. In either case, use pedological surveys in the planning and interpretation of any extensive survey. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every? Terminals should be of good quality to ensure that lowresistance contact is made at the electrodes and at the f57.
A soil box can be calibrated using solutions of known resistivity. Available pedological data should be used to facilitate interpretation. Surface contamination tends to concentrate in existing ditches with surface run-off, appreciably lowering the resistivity below the natural level.
The a spacing should equal the maximum depth of g5. Where resistivity information is included in published information, the measurement techniques used should be de? In the case of soil resistivity measurements, the repeatability may be characterized by a asfm of variation, Cv, representing the repeatability standard deviation divided by the average result and expressed in percent.
The multiparticipant test program results indicate a reproducibility Cv of Do not include large nonconductive bodies such as frozen soil, boulders, concrete foundations, etc. When a metallic structure is immersed in a conductive medium, the ability of the medium to carry current will in?
The resulting resistivity measurement represents the average resistivity of a hemisphere of soil of a radius equal to the electrode separation.
Measurements could be made in each soil classi?
Since a pipeline ditch cannot be included in the span of at-grade measurements, soil box samples should be obtained where the opportunity exists. More precise procedures may be employed in laboratory investigations and these should be de? The box should be readily cleanable to avoid contamination by previous samples. Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm. 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.
Measure the voltage drop across the inner electrodes and record both the current and voltage drop if a separate ammeter and voltmeter are used. Triplicate soil resistivity measurements by seven participants each using different meters. Risk and error must be arbitrarily selected to allow determination of the number of measurements. Both materials may require heat treatment so that they are sufficiently rigid to be inserted in dry or gravel soils.
The meter used may limit the upper range of resistivity, which can be measured. Originally published as G 57 — Using dimensional analysis, the correct unit for resistivity is ohm-centimetre.