ASTM D6639-18
(Guide)Standard Guide for Using the Frequency Domain Electromagnetic Method for Subsurface Site Characterizations
Standard Guide for Using the Frequency Domain Electromagnetic Method for Subsurface Site Characterizations
SIGNIFICANCE AND USE
5.1 Concepts:
5.1.1 This guide summarizes the equipment, field procedures and interpretation methods used for the characterization of subsurface materials and geological structure as based on their properties to conduct, enhance or obstruct the flow of electrical currents as induced in the ground by an alternating electromagnetic field.
5.1.2 The frequency domain method requires a transmitter or energy source, a transmitter coil, receiver electronics, a receiver coil, and interconnect cables (Fig. 5).
Perhaps the most important constraint is that the depth of penetration (skin depth, see section 6.5.3.1) of the electromagnetic wave generated by the transmitter be much greater than the intercoil spacing of the instrument. The depth of penetration is inversely proportional to the ground conductivity and instrument frequency. For example, an instrument with an intercoil spacing of 10 m and a frequency of 6400 Hz, using the vertical dipole, meets the low induction number assumption for earth conductivities less than 200 mS/m.
5.1.5 Multi-frequency domain instruments usually measure the two components of the secondary magnetic field: a component in-phase with the primary field and a component 90° out-of-phase (quadrature component) with the primary field (Kearey and Brook 1991). Generally, instruments do not display either the in-phase or out-of-phase (quadrature) components but do show either the apparent conductivity or the ratio of the secondary to primary magnetic fields.
5.1.6 When ground conditions are such that the low induction number approximation is valid, the in-phase component is much less than the quadrature phase component. If there is a relatively large in-phase component, the low induction number approximation is not valid and there is likely a very conductive buried body or layer, that is, ore body or man-made metal object.
5.1.7 The transmitter and receiver coils are almost always aligned in a plane either parallel to the earth's sur...
SCOPE
1.1 Purpose and Application:
1.1.1 This guide summarizes the equipment, field procedures, and interpretation methods for the assessment of subsurface conditions using the frequency domain electromagnetic (FDEM) method.
1.1.2 FDEM measurements as described in this standard guide are applicable to mapping subsurface conditions for geologic, geotechnical, hydrologic, environmental, agricultural, archaeological and forensic site characterizations as well as mineral exploration.
1.1.3 The FDEM method is sometimes used to map such diverse geologic conditions as depth to bedrock, fractures and fault zones, voids and sinkholes, soil and rock properties, and saline intrusion as well as man-induced environmental conditions including buried drums, underground storage tanks (USTs), landfill boundaries and conductive groundwater contamination.
1.1.4 The FDEM method utilizes the secondary magnetic field induced in the earth by a time-varying primary magnetic field to explore the subsurface. It measures the amplitude and phase of the induced field at various frequencies. FDEM instruments typically measure two components of the secondary magnetic field: a component in-phase with the primary field and a component 90° out-of-phase (quadrature component) with the primary field (Kearey and Brook 1991). Generally, the in-phase response is more sensitive to metallic items (either above or below the ground surface) while the quadrature response is more sensitive to geologic variations in the subsurface. However, both components are, to some degree, affected by both metallic and geologic features. FDEM measurements therefore are dependent on the electrical properties of the subsurface soil and rock or buried man-made objects as well as the orientation of any subsurface geological features or man-made objects. In many cases, the FDEM measurements can be used to identify the subsurface structure or object. This method is used only wh...
General Information
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Standards Content (Sample)
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: D6639 − 18
Standard Guide for
Using the Frequency Domain Electromagnetic Method for
1
Subsurface Site Characterizations
This standard is issued under the fixed designation D6639; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* can be used to identify the subsurface structure or object. This
methodisusedonlywhenitisexpectedthatthesubsurfacesoil
1.1 Purpose and Application:
or rock, man-made materials or geologic structure can be
1.1.1 This guide summarizes the equipment, field
characterized by differences in electrical conductivity.
procedures, and interpretation methods for the assessment of
1.1.5 The FDEM method may be used instead of the Direct
subsurface conditions using the frequency domain electromag-
Current Resistivity method (Guide D6431) when surface soils
netic (FDEM) method.
are excessively insulating (for example, dry or frozen) or a
1.1.2 FDEM measurements as described in this standard
layerofasphaltorplasticorotherlogisticalconstraintsprevent
guide are applicable to mapping subsurface conditions for
electrode to soil contact.
geologic, geotechnical, hydrologic, environmental,
agricultural, archaeological and forensic site characterizations
1.2 Limitations:
as well as mineral exploration.
1.2.1 This standard guide provides an overview of the
1.1.3 The FDEM method is sometimes used to map such
FDEMmethodusingcoplanarcoilsatorneargroundleveland
diverse geologic conditions as depth to bedrock, fractures and
has been referred to by other names including Slingram,
fault zones, voids and sinkholes, soil and rock properties, and
HLEM(horizontalloopelectromagnetic)andGroundConduc-
saline intrusion as well as man-induced environmental condi-
tivity methods. This guide does not address the details of the
tions including buried drums, underground storage tanks
electromagnetictheory,fieldproceduresorinterpretationofthe
(USTs), landfill boundaries and conductive groundwater con-
data. References are included that cover these aspects in
tamination.
greater detail and are considered an essential part of this guide
1.1.4 The FDEM method utilizes the secondary magnetic
(Grant and West, 1965; Wait, 1982; Kearey and Brook, 1991;
field induced in the earth by a time-varying primary magnetic
Milsom,1996;Ward,1990).Itisrecommendedthattheuserof
field to explore the subsurface. It measures the amplitude and
the FDEM method review the relevant material pertaining to
phase of the induced field at various frequencies. FDEM
their particular application. ASTM standards that should also
instruments typically measure two components of the second-
be consulted include Guide D420, Terminology D653, Guide
arymagneticfield:acomponentin-phasewiththeprimaryfield
D5730, Guide D5753, Practice D6235, Guide D6429, and
and a component 90° out-of-phase (quadrature component)
Guide D6431.
withtheprimaryfield(KeareyandBrook1991).Generally,the
1.2.2 Thisguideislimitedtofrequencydomaininstruments
in-phase response is more sensitive to metallic items (either
using a coplanar orientation of the transmitting and receiving
above or below the ground surface) while the quadrature
coils in either the horizontal dipole (HD) mode with coils
response is more sensitive to geologic variations in the
vertical, or the vertical dipole (VD) mode with coils horizontal
subsurface. However, both components are, to some degree,
(Fig. 2). It does not include coaxial or asymmetrical coil
affected by both metallic and geologic features. FDEM mea-
orientations,whicharesometimesusedforspecialapplications
surements therefore are dependent on the electrical properties
(Grant and West 1965).
of the subsurface soil and rock or buried man-made objects as
1.2.3 This guide is limited to the use of frequency domain
well as the orientation of any subsurface geological features or
instruments in which the ratio of the induced secondary
man-made objects. In many cases, the FDEM measurements
magnetic field to the primary magnetic field is directly propor-
tionaltotheground’sbulkorapparentconductivity(see5.1.4).
Instruments that give a direct measurement of the apparent
1
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock
ground conductivity are commonly referred to as Ground
and is the direct responsibility of Subcommittee D18.01 on Surface and Subsurface
Characterization.
Conductivity Meters (GCMs) that are designed to operate
Current edition approved Feb. 1, 2018. Published March 2018. Origi
...
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