1、Designation: D6431 18Standard Guide forUsing the Direct Current Resistivity Method for SubsurfaceSite Characterization1This standard is issued under the fixed designation D6431; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 Purpose and Application:1.1.1 This guide summarizes the equipment, fieldprocedures, and interpretation methods
3、 for the assessment ofthe electrical properties of subsurface materials and their porefluids, using the direct current (DC) resistivity method. Mea-surements of the electrical properties of subsurface materialsare made from the land surface and yield an apparent resistiv-ity. These data can then be
4、interpreted to yield an estimate ofthe depth, thickness, voids, and resistivity of subsurfacelayer(s).1.1.2 Resistivity measurements as described in this guideare applied in geological, geotechnical, environmental, andhydrologic investigations. The resistivity method is used tomap geologic features
5、such as lithology, structure, fractures,and stratigraphy; hydrologic features such as depth to watertable, depth to aquitard, and groundwater salinity; and todelineate groundwater contaminants. General references are,Keller and Frischknecht (1),2Zohdy et al (2), Koefoed (3),EPA(4), Ward (5), Griffit
6、hs and King (6), and Telford et al (7).1.1.3 This guide does not address the use tomographicinterpretation methods, commonly referred to as electricalresistivity tomography (ERT) or electrical resistivity imaging(ERI). While many of the principles apply the data acquisitionand interpretation differ
7、from those set forth in this guide.1.2 Limitations:1.2.1 This guide provides an overview of the Direct CurrentResistivity Method. It does not address in detail the theory,field procedures, or interpretation of the data. Numerousreferences are included for that purpose and are considered anessential
8、part of this guide. It is recommended that the user ofthe resistivity method be familiar with the references cited inthe text and with the Guide D420, Practice D5088, PracticeD5608, Guide D5730, Test Method G57, D6429, and D6235.1.2.2 This guide is limited to the commonly used approachfor resistivit
9、y measurements using sounding and profilingtechniques with the Schlumberger, Wenner, or dipole-dipolearrays and modifications to those arrays. It does not cover theuse of a wide range of specialized arrays. It also does notinclude the use of spontaneous potential (SP) measurements,induced polarizati
10、on (IP) measurements, or complex resistivitymethods.1.2.3 The resistivity method has been adapted for a numberof special uses, on land, within a borehole, or on water.Discussions of these adaptations of resistivity measurementsare not included in this guide.1.2.4 The approaches suggested in this gui
11、de for the resis-tivity method are the most commonly used, widely acceptedand proven; however, other approaches or modifications to theresistivity method that are technically sound may be substitutedif technically justified and documented.1.2.5 This guide offers an organized collection of informa-ti
12、on or a series of options and does not recommend a specificcourse of action. This document cannot replace education orexperience and should be used in conjunction with professionaljudgements. Not all aspects of this guide may be applicable inall circumstances. This ASTM standard is not intended tore
13、present or replace the standard of care by which theadequacy of a given professional service must be judged, norshould this document be applied without consideration of aprojects many unique aspects. The word “Standard” in thetitle of this document means only that the document has beenapproved throu
14、gh the ASTM consensus process.1.3 UnitsThe values stated in SI units are to be regardedas standard. No other units of measurement are included in thisstandard. Reporting of test results in units other than SI shallnot be regarded as nonconformance with this test method.1.4 Precautions:1.4.1 It is th
15、e responsibility of the user of this guide tofollow any precautions in the equipment manufacturers rec-ommendations and to consider the safety implications whenhigh voltages and currents are used.1.4.2 If this guide is used at sites with hazardous materials,operations, or equipment, it is the respon
16、sibility of the user ofthis guide to establish appropriate safety and health practicesand to determine the applicability of regulations prior to use.1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.01 on Surface and Subsu
17、rfaceCharacterization.Current edition approved Feb. 1, 2018. Published March 2018. Originallyapproved in 1999. Last previous edition approved in 2010 as D643199(2010).DOI: 10.1520/D6431-18.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.*A Summary of C
18、hanges section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the
19、Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.11.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresp
20、onsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-iz
21、ation established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3D420 Guide to Site Characterization for Engineering
22、Designand Construction PurposesD653 Terminology Relating to Soil, Rock, and ContainedFluidsD5088 Practice for Decontamination of Field EquipmentUsed at Waste SitesD5608 Practices for Decontamination of Sampling and NonSample Contacting Equipment Used at Low Level Radio-active Waste SitesD5730 Guide
23、for Site Characterization for EnvironmentalPurposes With Emphasis on Soil, Rock, the Vadose Zoneand Groundwater (Withdrawn 2013)4D5753 Guide for Planning and Conducting GeotechnicalBorehole Geophysical LoggingD6235 Practice for Expedited Site Characterization of Va-dose Zone and Groundwater Contamin
24、ation at HazardousWaste Contaminated SitesD6429 Guide for Selecting Surface Geophysical MethodsG57 Test Method for Field Measurement of Soil ResistivityUsing the Wenner Four-Electrode Method3. Terminology3.1 Definitions:3.1.1 For common definitions of terms used in this standard,see Terminology D653
25、.3.1.2 The majority of the technical terms used in thisdocument are defined in Sheriff (1991).3.2 Additional Definitions:3.2.1 apparent resistivity, nthe resistivity ofhomogeneous, isotropic ground that would give the samevoltage-current relationship as measured.3.2.1.1 DiscussionApparent resistivit
26、y is expressed inohm-meter (m).3.2.2 conductivity, nthe ability of a material to conduct anelectrical current. In isotropic material, it is the reciprocal ofresistivity.3.2.2.1 DiscussionConductivity is measured in Siemensper meter (S/m).3.2.3 resistance, nopposition to the flow of direct current.3.
27、2.3.1 DiscussionResistance is measured in ohm ().3.2.4 resistivity, nthe property of a material that resists theflow of electrical current.3.2.4.1 DiscussionResistivity is measured in ohm-meter(m).4. Summary of Guide4.1 SummaryThe measurement of electrical resistivityrequires that four electrodes be
28、 placed in contact with thesurface materials (Fig. 1). The geometry and separation of theelectrode array are selected on the basis of the application andrequired depth of the site characterization.4.1.1 In an electrical resistivity survey, a direct current or avery low frequency alternating current
29、is passed into theground through a pair of current electrodes (C1 and C2), andthe resulting potential drop is measured across a pair ofpotential electrodes (P1 and P2) as shown in Fig. 1. Theresistance is then derived as the ratio of the voltage measuredacross the potential electrodes and the measur
30、ed appliedcurrent. The apparent resistivity of subsurface materials isderived as the resistance multiplied by a geometric factor thatis determined by the geometry and spacing of the electrodearray.4.1.2 The calculated apparent resistivity measurement rep-resents a bulk average resistivity of the vol
31、ume of earthdetermined by the geometry of the array and the resistivity ofthe subsurface material. This apparent resistivity is differentfrom true resistivity unless the subsurface materials are elec-trically uniform. Representative resistivity values of layers areinterpreted from apparent resistivi
32、ty values obtained from aseries of measurements made with variable electrode spacing.Increasing electrode spacing may permit distinction amonglayers that vary in electrical properties with depth.4.1.3 Most resistivity surveys for geologic, engineering,hydrologic, and environmental applications are c
33、arried out todetermine depths of specific layers or lateral changes ingeologic conditions at depths of less than a hundred metres.However, with sufficient power and instrument sensitivity,resistivity measurements are made to depths of several hundredmetres.4.2 Complementary DataOther complementary s
34、urfacegeophysical methods (D6429) or borehole geophysical meth-ods (Guide D5753) and non-geophysical methods may benecessary to properly interpret subsurface conditions.5. Significance and Use5.1 ConceptsThe resistivity technique is used to measurethe resistivity of subsurface materials. Although th
35、e resistivityof materials can be a good indicator of the type of subsurfacematerial present, it is not a unique indicator. While theresistivity method is used to measure the resistivity of earthmaterials, it is the interpreter who, based on knowledge of localgeologic conditions and other data, must
36、interpret resistivitydata and arrive at a reasonable geologic and hydrologicinterpretation.5.2 Parameter Being Measured and Representative Values:3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
37、 volume information, refer to the standards Document Summary page onthe ASTM website.4The last approved version of this historical standard is referenced onwww.astm.org.D6431 1825.2.1 Table 1 shows some general trends for resistivityvalues. Fig. 2 shows ranges in resistivity values for subsurfacemat
38、erials.5.2.2 Materials with either a low effective porosity or thatlack conductive pore fluids have a relatively high resistivity(1000 m). These materials include massive limestones,most unfractured igneous rocks, unsaturated unconsolidatedmaterials, and ice.5.2.3 Materials that have high porosity w
39、ith conductive porefluids or that consist of or contain clays usually have lowresistivity. These include clay soil and weathered rock.5.2.4 Materials whose pore water has low salinity havemoderately high resistivity.5.2.5 The dependence of resistivity on water saturation isnot linear. Resistivity in
40、creases relatively little as saturationdecreases from 100 % to somewhere between 40 and 60 % andthen increases much more as saturation continues to decrease.An empirical relationship known asArchies Law describes therelationship between pore fluid resistivity, porosity, and bulkresistivity (McNeill
41、(10).5.3 EquipmentGeophysical apparatus used for surfaceresistivity measurement includes a source of power, a means tomeasure the current, a high impedance voltmeter, electrodes tomake contact with the ground, and the necessary cables toconnect the electrodes to the power sources and the volt meter(
42、Fig. 1).5.3.1 While resistivity measurements can be made usingcommon electronic instruments, it is recommended that com-mercial resistivity instruments specifically designed for thepurpose be used for resistivity measurements in the field.5.3.2 Care must be taken to ensure good electrical contact of
43、the electrodes with the ground. Electrodes should be driveninto the ground until they are in firm contact. If connectionsbetween electrodes and the insulated wire are not waterproof,care must be taken to ensure that they will not be shorted outby moisture. Special waterproof cables and connectors ar
44、erequired for wet areas.5.3.3 A large variety of resistivity systems are availablefrom different manufacturers. Relatively inexpensive battery-powered units are available for shallow surveys. The currentsource (transmitter) and the potential measurement instrumentFIG. 1 Diagram Showing Basic Concept
45、 of Resistivity Measurement (from Benson et al, (8)TABLE 1 Representative Resistivity Values for Soil, Water, andRock (Mooney (4)Regional Soil Resistivity m- wet regions 50 to 200- dry regions 100 to 500- arid regions 200 to 1000 (sometimes as low as 50 if thesoil is saline)Water Type m- soil water
46、1 to 100- rain water 30 to 1000- sea water order of 0.2- ice 105 to 108Earth Material Types m- igneous and metamorphic 100 to 10,000- consolidated sediments 10 to 100- unconsolidated sediments 1 to 100D6431 183(receiver) are often assembled into a single, portable unit. Insome cases, the transmitter
47、 and receiver units are separate.High power units capable of deep survey work are powered bygenerators. The current used in dc resistivity surveys variesfrom a few milliamps to several amps, depending on the depthof the site characterization.5.3.4 Signal EnhancementSignal enhancement capabilityis av
48、ailable in many resistivity systems. It is a significant aidwhen working in noisy areas or with low power sources.Enhancement is accomplished by adding the results from anumber of measurements at the same station. This processincreases the signal-to-noise ratio.5.4 Limitations and Interferences:5.4.
49、1 Limitations Inherent to Geophysical Methods:5.4.1.1 Afundamental limitation of all geophysical methodslies in the fact that a given set of data cannot be associated witha unique set of subsurface conditions. In most situations,surface geophysical measurements alone cannot resolve allambiguities, and some additional information, such as boreholedata, is required. Because of this inherent limitation in geo-physical methods, a resistivity survey alone is never considereda complete assessment of subsurface conditions. Properlyintegrated with other informati
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