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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A nomograph for this correction is shown in Fig. A number in parentheses indicates the year of last reapproval. Where mean or median values cannot be estimated with reasonable accuracy, sequential sampling techniques can be employed. 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.
Planning and Interpretation 7.
This can be done by preparing a stiff slurry of adtm 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. Otherwise, use t57 water. 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.
Where available, use ground water from the sample excavation for saturation.
Surface contamination tends to concentrate in existing ditches with surface run-off, appreciably lowering the resistivity below the natural level. Your comments will receive careful consideration at a meeting of the responsible technical committee, asttm you may attend. Surplus water should not be poured off xstm this will remove soluble constituents. 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.
Current edition approved April 15, The latter method permits precise mathematical treatment, such as cumulative probability analysis. The former method is suited to graphical presentation and plotting resistivity versus distance, and will identify gradients and abrupt changes in soil condition. Sharp changes in resistivity with distance and appreciable variations in moisture content and drainage are indicative of local severe conditions.
The soil should be well-compacted in layers in the soil box, with air spaces eliminated as far as practicable. Summary of Test Method 3.
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. Y57 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 multi-participant test program results indicate a repeatability Cv of 6. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters. The degree of electrode polarization will also affect the size of such currents.
Active Risk Management
Since the number of soil sections that could be inspected is essentially unlimited, in? The data from this evaluation are available from ASTM in a research report.
The a spacing should equal the maximum depth of interest. Since most pipelines are installed at depths of from 1. Measurements could be made in each soil classi? It will also be necessary to prepare a mixed sample. Aetm electrode separation should be selected with consideration of the soil strata of interest. Risk and error must be arbitrarily selected to allow determination of the number of measurements.
The multiparticipant test program results indicate a reproducibility Cv of In either case, use pedological surveys in the planning and interpretation of any extensive survey. xstm
Asgm effect of variations in compaction and moisture content can be reduced by fully saturating the sample before placing it in the box. It is desirable to sample each type separately. Measure the voltage drop across the inner electrodes and record both the current and voltage drop if a separate ammeter and voltmeter are used.
These commonly use two electrodes mounted on a prod that is inserted in the soil-at-grade in an excavation or a driven or atm hole.
ASTM Ga (Reapproved )_百度文库
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 current can be provided by either a cranked ac generator or a vibrator-equipped dc source.
The mean and median resistivity values will indicate the general corrosivity of the soil. The box should be readily cleanable to avoid contamination by previous sstm. Conductive structures such as pipes and cables should not be within 1?
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 soil box g557 be calibrated using solutions of known resistivity. If error exceeds this limit, prepare a calibration curve and correct all measurements accordingly. Do not include large nonconductive bodies such as frozen soil, boulders, concrete foundations, etc. Terminals should be of good quality to ensure that lowresistance contact is made at the electrodes and at the meter.
Users of this standard are expressly advised that determination of the validity of any such patent rights, and the g577 of infringement of such rights, are entirely their own responsibility.
ASTM G57 Standard
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 electrodes should be formed with sstm handle and a FIG. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every? Triplicate soil resistivity measurements by seven participants each using different meters.
Where regular surveys are to be made at? Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm.