ASTM D6431-18
(Guide)Standard Guide for Using the Direct Current Resistivity Method for Subsurface Site Characterization
Standard Guide for Using the Direct Current Resistivity Method for Subsurface Site Characterization
SIGNIFICANCE AND USE
5.1 Concepts—The resistivity technique is used to measure the resistivity of subsurface materials. Although the resistivity of materials can be a good indicator of the type of subsurface material present, it is not a unique indicator. While the resistivity method is used to measure the resistivity of earth materials, it is the interpreter who, based on knowledge of local geologic conditions and other data, must interpret resistivity data and arrive at a reasonable geologic and hydrologic interpretation.
5.2 Parameter Being Measured and Representative Values:
5.2.1 Table 1 shows some general trends for resistivity values. Fig. 2 shows ranges in resistivity values for subsurface materials.
5.6.2 Schlumberger Array—The Schlumberger array consists of unequally spaced in-line electrodes (Fig. 3), where AB > 5 MN. The formula for calculating apparent resistivity from a Schlumberger measurement is:
where:
AB = distance between current electrodes, and MN = distance between potential electrodes.
5.6.3 Dipole-Dipole Array—The dipole-dipole array consists of a pair of closely spaced current electrodes and a pair of closely spaced potential electrodes (Fig. 3). The formula for calculating apparent resistivity from a dipole-dipole measurement is:
where:
na = distance between innermost electrodes measured as a number (n) of a-spacings, and a = distance between the current electrodes and also the potential electrodes.
5.6.4 Comparison of the Arrays:
5.6.4.1 Schlumberger Arrays:
(1) Schlumberger arrays are less susceptible to contact problems and the influence of nearby geologic conditions that may affect readings. The method provides a means to recognize the effects of lateral variations and to partially correct for them.
(2) Schlumberger arrays are slightly faster in field operations since only the current electrodes must be moved between readings.
5.6.4.2 Wenner Arrays:
(1) The Wenner array provid...
SCOPE
1.1 Purpose and Application:
1.1.1 This guide summarizes the equipment, field procedures, and interpretation methods for the assessment of the electrical properties of subsurface materials and their pore fluids, using the direct current (DC) resistivity method. Measurements of the electrical properties of subsurface materials are made from the land surface and yield an apparent resistivity. These data can then be interpreted to yield an estimate of the depth, thickness, voids, and resistivity of subsurface layer(s).
1.1.2 Resistivity measurements as described in this guide are applied in geological, geotechnical, environmental, and hydrologic investigations. The resistivity method is used to map geologic features such as lithology, structure, fractures, and stratigraphy; hydrologic features such as depth to water table, depth to aquitard, and groundwater salinity; and to delineate groundwater contaminants. General references are, Keller and Frischknecht (1),2 Zohdy et al (2), Koefoed (3), EPA(4), Ward (5), Griffiths and King (6), and Telford et al (7).
1.1.3 This guide does not address the use tomographic interpretation methods, commonly referred to as electrical resistivity tomography (ERT) or electrical resistivity imaging (ERI). While many of the principles apply the data acquisition and interpretation differ from those set forth in this guide.
1.2 Limitations:
1.2.1 This guide provides an overview of the Direct Current Resistivity Method. It does not address in detail the theory, field procedures, or interpretation of the data. Numerous references are included for that purpose and are considered an essential part of this guide. It is recommended that the user of the resistivity method be familiar with the references cited in the text and with the Guide D420, Practice D5088, Practice D5608, Guide D5730, Test Method G57, D6429, and D6235.
1.2.2 This guide is limited to the commonly used approach fo...
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6431 − 18
Standard Guide for
Using the Direct Current Resistivity Method for Subsurface
1
Site Characterization
This standard is issued under the fixed designation D6431; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 1.2.2 This guide is limited to the commonly used approach
for resistivity measurements using sounding and profiling
1.1 Purpose and Application:
techniques with the Schlumberger, Wenner, or dipole-dipole
1.1.1 This guide summarizes the equipment, field
arrays and modifications to those arrays. It does not cover the
procedures, and interpretation methods for the assessment of
use of a wide range of specialized arrays. It also does not
the electrical properties of subsurface materials and their pore
include the use of spontaneous potential (SP) measurements,
fluids, using the direct current (DC) resistivity method. Mea-
induced polarization (IP) measurements, or complex resistivity
surements of the electrical properties of subsurface materials
methods.
are made from the land surface and yield an apparent resistiv-
1.2.3 The resistivity method has been adapted for a number
ity. These data can then be interpreted to yield an estimate of
of special uses, on land, within a borehole, or on water.
the depth, thickness, voids, and resistivity of subsurface
Discussions of these adaptations of resistivity measurements
layer(s).
are not included in this guide.
1.1.2 Resistivity measurements as described in this guide
1.2.4 The approaches suggested in this guide for the resis-
are applied in geological, geotechnical, environmental, and
tivity method are the most commonly used, widely accepted
hydrologic investigations. The resistivity method is used to
and proven; however, other approaches or modifications to the
map geologic features such as lithology, structure, fractures,
resistivitymethodthataretechnicallysoundmaybesubstituted
and stratigraphy; hydrologic features such as depth to water
if technically justified and documented.
table, depth to aquitard, and groundwater salinity; and to
1.2.5 This guide offers an organized collection of informa-
delineate groundwater contaminants. General references are,
2
tion or a series of options and does not recommend a specific
Keller and Frischknecht (1), Zohdy et al (2), Koefoed (3),
course of action. This document cannot replace education or
EPA(4), Ward (5), Griffiths and King (6), and Telford et al (7).
experienceandshouldbeusedinconjunctionwithprofessional
1.1.3 This guide does not address the use tomographic
judgements. Not all aspects of this guide may be applicable in
interpretation methods, commonly referred to as electrical
all circumstances. This ASTM standard is not intended to
resistivity tomography (ERT) or electrical resistivity imaging
represent or replace the standard of care by which the
(ERI). While many of the principles apply the data acquisition
adequacy of a given professional service must be judged, nor
and interpretation differ from those set forth in this guide.
should this document be applied without consideration of a
1.2 Limitations:
project’s many unique aspects. The word “Standard” in the
1.2.1 This guide provides an overview of the Direct Current
title of this document means only that the document has been
Resistivity Method. It does not address in detail the theory,
approved through the ASTM consensus process.
field procedures, or interpretation of the data. Numerous
1.3 Units—The values stated in SI units are to be regarded
references are included for that purpose and are considered an
as standard. No other units of measurement are included in this
essential part of this guide. It is recommended that the user of
standard. Reporting of test results in units other than SI shall
the resistivity method be familiar with the references cited in
not be regarded as nonconformance with this test method.
the text and with the Guide D420, Practice D5088, Practice
D5608, Guide D5730, Test Method G57, D6429, and D6235.
1.4 Precautions:
1.4.1 It is the responsibility of the user of this guide to
follow any precautions in the equipment manufacturer’s rec-
1
This guide is under the jurisdiction ofASTM CommitteeD18 on Soil and Rock
ommendations and to consider the safety implications when
and is the direct responsibility of Subcommittee D18.01 on Surface and Subsurface
high voltages and currents are used.
Characterization.
Current edition approved Feb. 1, 2018. Publis
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6431 − 99 (Reapproved 2010) D6431 − 18
Standard Guide for
Using the Direct Current Resistivity Method for Subsurface
1
InvestigationSite Characterization
This standard is issued under the fixed designation D6431; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 Purpose and Application:
1.1.1 This guide summarizes the equipment, field procedures, and interpretation methods for the assessment of the electrical
properties of subsurface materials and their pore fluids, using the direct current (DC) resistivity method. Measurements of the
electrical properties of subsurface materials are made from the land surface and yield an apparent resistivity. These data can then
be interpreted to yield an estimate of the depth, thickness, voids, and resistivity of subsurface layer(s).
1.1.2 Resistivity measurements as described in this guide are applied in geological, geotechnical, environmental, and hydrologic
investigations. The resistivity method is used to map geologic features such as lithology, structure, fractures, and stratigraphy;
hydrologic features such as depth to water table, depth to aquitard, and groundwater salinity; and to delineate groundwater
2
contaminants. General references are, Keller and Frischknecht (1), Zohdy et al (2), Koefoed (3), EPA(4), Ward (5), Griffiths and
King (6), and Telford et al (7).
1.1.3 This guide does not address the use tomographic interpretation methods, commonly referred to as electrical resistivity
tomography (ERT) or electrical resistivity imaging (ERI). While many of the principles apply the data acquisition and
interpretation differ from those set forth in this guide.
1.2 Limitations:
1.2.1 This guide provides an overview of the Direct Current Resistivity Method. It does not address in detail the theory, field
procedures, or interpretation of the data. Numerous references are included for that purpose and are considered an essential part
of this guide. It is recommended that the user of the resistivity method be familiar with the references cited in the text and with
the Guide D420, Practice D5088, Practice D5608, Guide D5730, Test Method G57, D6429, and D6235.
1.2.2 This guide is limited to the commonly used approach for resistivity measurements using sounding and profiling techniques
with the Schlumberger, Wenner, or dipole-dipole arrays and modifications to those arrays. It does not cover the use of a wide range
of specialized arrays. It also does not include the use of spontaneous potential (SP) measurements, induced polarization (IP)
measurements, or complex resistivity methods.
1.2.3 The resistivity method has been adapted for a number of special uses, on land, within a borehole, or on water. Discussions
of these adaptations of resistivity measurements are not included in this guide.
1.2.4 The approaches suggested in this guide for the resistivity method are the most commonly used, widely accepted and
proven; however, other approaches or modifications to the resistivity method that are technically sound may be substituted if
technically justified and documented.
1.2.5 This guide offers an organized collection of information or a series of options and does not recommend a specific course
of action. This document cannot replace education or experience and should be used in conjunction with professional judgements.
Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace
the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied
without consideration of a project’s many unique aspects. The word “Standard” in the title of this document means only that the
document has been approved through the ASTM consensus process.
1
This guide is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.01 on Surface and Subsurface
Characterization.
Current edition approved May 1, 2010Feb. 1, 2018. Published September 2010March 2018. Originally approved in 1999. Last previous edition approved in 20052010 as
D6431–99(2005).D6431–99(2010). DOI: 10.1520/D6431-99R10.10.1520/D6431-18.
2
The boldface numbers in parentheses refer to the list of references at the end of this standard.
*A Summa
...
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