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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This standard is subject to revision at any time by the responsible technical committee and must be reviewed every? The current can be provided by either a cranked ac generator or a vibrator-equipped dc source. Where available, use ground water from the sample excavation for saturation.
ASTM G57 Standard
A soil box can be calibrated using solutions of known resistivity. 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. Measurements could be made in astj soil classi?
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It will also be necessary to prepare a mixed sample. If error exceeds this limit, prepare a calibration curve and correct all measurements accordingly.
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. The latter method permits precise mathematical treatment, such as cumulative probability analysis. 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.
When a metallic structure is immersed in a conductive medium, the ability of the medium to carry current will in? Sharp changes in resistivity with distance and appreciable variations in moisture content and drainage are indicative of local severe conditions.
The meter used may limit the upper range of resistivity, which can be measured. A nomograph for this correction is shown in Fig. The former method is suited to graphical presentation and plotting resistivity versus distance, and will identify gradients and abrupt changes in soil condition. The a spacing should equal the maximum depth of interest.
Conductive structures such as pipes and cables should not be within 1? The resulting resistivity measurement represents the average resistivity of a hemisphere of soil of a radius equal to the electrode separation.
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Since most pipelines are installed at depths of from 1. 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. Do not include large nonconductive bodies such as aastm soil, boulders, concrete foundations, etc. More precise procedures may be employed in laboratory investigations and these should be de?
Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. Originally published as G 57 — adtm Where resistivity information is included in published information, the measurement techniques used should be de?
Current edition approved April 15, A superscript epsilon e indicates an editorial change since the last revision or reapproval.
If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below. Triplicate soil resistivity measurements by seven participants each using different meters. Both materials may require heat treatment so that they are sufficiently rigid to be inserted in dry or gravel soils. 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.
Last previous edition G 57 — t57 Surface contamination tends to concentrate in existing ditches with surface run-off, appreciably lowering the resistivity below the natural level.
Your comments are invited either for revision of this standard or for additional standards and axtm be addressed to ASTM Headquarters. The data from this evaluation are available from ASTM in a research report. This method permits the determination of the probability of the presence of a aatm with a resistivity equal to or greater than a particular value.
Where a resistivity meter is used, read the resistance directly and record. 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. 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.
Alternatively, the resistance can be measured directly. Where mean or median values cannot be estimated with reasonable accuracy, sequential sampling techniques can be employed.
Surplus water should not be poured off as this will remove soluble constituents.