ASTM D6432-99(2005)
(Guide)Standard Guide for Using the Surface Ground Penetrating Radar Method for Subsurface Investigation
Standard Guide for Using the Surface Ground Penetrating Radar Method for Subsurface Investigation
SCOPE
1.1 Purpose and Application:
1.1.1 This guide covers the equipment, field procedures, and interpretation methods for the assessment of subsurface materials using the impulse Ground Penetrating Radar (GPR) Method. GPR is most often employed as a technique that uses high-frequency electromagnetic (EM) waves (from 10 to 3000 MHz) to acquire subsurface information. GPR detects changes in EM properties (dielectric permittivity, conductivity, and magnetic permeability), that in a geologic setting, are a function of soil and rock material, water content, and bulk density. Data are normally acquired using antennas placed on the ground surface or in boreholes. The transmitting antenna radiates EM waves that propagate in the subsurface and reflect from boundaries at which there are EM property contrasts. The receiving GPR antenna records the reflected waves over a selectable time range. The depths to the reflecting interfaces are calculated from the arrival times in the GPR data if the EM propagation velocity in the subsurface can be estimated or measured.
1.1.2 GPR measurements as described in this guide are used in geologic, engineering, hydrologic, and environmental applications. The GPR method is used to map geologic conditions that include depth to bedrock, depth to the water table (Wright et al (1)²), depth and thickness of soil strata on land and under fresh water bodies (Beres and Haeni (2)), and the location of subsurface cavities and fractures in bedrock (Ulriksen (3) and Imse and Levine (4)). Other applications include the location of objects such as pipes, drums, tanks, cables, and boulders , mapping landfill and trench boundaries (Benson et al (6)), mapping contaminants (Cosgrave et al (7); Brewster and Annan (8); Daniels et al (9)), conducting archaeological (Vaughan (10)) and forensic investigations (Davenport et al (11)), inspection of brick, masonry, and concrete structures, roads and railroad trackbed studies (Ulriksen (3)), and highway bridge scour studies (Placzek and Haeni (12)). Additional applications and case studies can be found in the various Proceedings of the International Conferences on Ground Penetrating Radar (Lucius et al (13); Hannien and Autio, (14), Redman, (15); Sato, (16); Plumb (28)), various Proceedings of the Symposium on the Application of Geophysics to Engineering and Environmental Problems (Environmental and Engineering Geophysical Society, 1988-1998), and The Ground Penetrating Radar Workshop (Pilon (18)), EPA ((19)), and Daniels (20) provide overviews of the GPR method.
1.2 Limitations:
1.2.1 This guide provides an overview of the impulse GPR method. It does not address details of the theory, field procedures, or interpretation of the data. References are included for that purpose and are considered an essential part of this guide. It is recommended that the user of the GPR method be familiar with the relevant material within this guide and the references cited in the text and with Guides D 420, D 5730, D 5753, D 6429, and D 6235.
1.2.2 This guide is limited to the commonly used approach to GPR measurements from the ground surface. The method can be adapted for a number of special uses on ice (Haeni et al (21); Wright et al (22)), within or between boreholes (Lane et al (23); Lane et al (24)), on water (Haeni (25)), and airborne (Arcone et al (25)) applications. A discussion of these other adaptations of GPR measurements is not included in this guide.
1.2.3 The approaches suggested in this guide for using GPR are the most commonly used, widely accepted, and proven; however, other approaches or modifications to using GPR that are technically sound may be substituted if technically justified and documented.
1.2.4 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 aspec...
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Designation: D6432 – 99 (Reapproved 2005)
Standard Guide for
Using the Surface Ground Penetrating Radar Method for
Subsurface Investigation
This standard is issued under the fixed designation D6432; 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 roadsandrailroadtrackbedstudies(Ulriksen (3)),andhighway
bridge scour studies (Placzek and Haeni (12)). Additional
1.1 Purpose and Application:
applications and case studies can be found in the various
1.1.1 Thisguidecoverstheequipment,fieldprocedures,and
Proceedings of the International Conferences on Ground
interpretation methods for the assessment of subsurface mate-
Penetrating Radar(Luciusetal (13);HannienandAutio, (14),
rials using the impulse Ground Penetrating Radar (GPR)
Redman, (15); Sato, (16); Plumb (17)), various Proceedings of
Method. GPR is most often employed as a technique that uses
the Symposium on the Application of Geophysics to Engineer-
high-frequency electromagnetic (EM) waves (from 10 to 3000
ing and Environmental Problems (Environmental and Engi-
MHz) to acquire subsurface information. GPR detects changes
neering Geophysical Society, 1988–1998), and The Ground
in EM properties (dielectric permittivity, conductivity, and
Penetrating Radar Workshop (Pilon (18)), EPA (19), and
magnetic permeability), that in a geologic setting, are a
Daniels (20) provide overviews of the GPR method.
function of soil and rock material, water content, and bulk
1.2 Limitations:
density. Data are normally acquired using antennas placed on
1.2.1 This guide provides an overview of the impulse GPR
the ground surface or in boreholes. The transmitting antenna
method. It does not address details of the theory, field proce-
radiates EM waves that propagate in the subsurface and reflect
dures,orinterpretationofthedata.Referencesareincludedfor
fromboundariesatwhichthereareEMpropertycontrasts.The
that purpose and are considered an essential part of this guide.
receiving GPR antenna records the reflected waves over a
ItisrecommendedthattheuseroftheGPRmethodbefamiliar
selectabletimerange.Thedepthstothereflectinginterfacesare
with the relevant material within this guide and the references
calculated from the arrival times in the GPR data if the EM
citedinthetextandwithGuidesD420,D5730,D5753,D6429,
propagation velocity in the subsurface can be estimated or
and D6235.
measured.
1.2.2 This guide is limited to the commonly used approach
1.1.2 GPRmeasurementsasdescribedinthisguideareused
to GPR measurements from the ground surface. The method
in geologic, engineering, hydrologic, and environmental appli-
canbeadaptedforanumberofspecialusesonice(Haenietal
cations. The GPR method is used to map geologic conditions
(21); Wright et al (22)), within or between boreholes (Lane et
that include depth to bedrock, depth to the water table (Wright
2 al (23); Lane et al (24)), on water (Haeni (25)), and airborne
et al (1) ), depth and thickness of soil strata on land and under
(Arcone et al (25)) applications. A discussion of these other
fresh water bodies (Beres and Haeni (2)), and the location of
adaptationsofGPRmeasurementsisnotincludedinthisguide.
subsurface cavities and fractures in bedrock (Ulriksen (3) and
1.2.3 TheapproachessuggestedinthisguideforusingGPR
Imse and Levine (4)). Other applications include the location
are the most commonly used, widely accepted, and proven;
of objects such as pipes, drums, tanks, cables, and boulders ,
however, other approaches or modifications to using GPR that
mapping landfill and trench boundaries (Benson et al (6)),
aretechnicallysoundmaybesubstitutediftechnicallyjustified
mapping contaminants (Cosgrave et al (7); Brewster and
and documented.
Annan (8); Daniels et al (9)), conducting archaeological
1.2.4 This guide offers an organized collection of informa-
(Vaughan (10)) and forensic investigations (Davenport et al
tion or a series of options and does not recommend a specific
(11)), inspection of brick, masonry, and concrete structures,
course of action. This document cannot replace education or
experienceandshouldbeusedinconjunctionwithprofessional
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock
judgements. Not all aspects of this guide may be applicable in
and is the direct responsibility of Subcommittee D18.01 on Surface and Subsurface
all circumstances. This ASTM standard is not intended to
Characterization.
represent or replace the standard of care by which the
Current edition approved May 1, 2005. Published December 2005. Originally
approved in 1999. Last previous edition approved in 1999 as D6432–99. DOI: adequacy of a given professional service must be judged, nor
10.1520/D6432-99R05.
should this document be applied without consideration of a
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
project’s many unique aspects. The word “Standard” in the
this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6432 – 99 (2005)
title of this document means only that the document has been including conduction currents, dielectric relaxation, scattering,
approved through the ASTM consensus process. and geometrical spreading.
1.3 Precautions:
3.1.3.3 bandwidth—The operating frequency range of an
1.3.1 It is the responsibility of the user of this guide to
antenna that conforms to a specified standard (Balanis (28)).
follow any precautions in the equipment manufacturer’s rec-
For GPR antennas, typically the bandwidth is defined by the
ommendations and to establish appropriate health and safety
upper and lower frequencies radiated from a transmitting GPR
practices.
antenna that possess power that is 3 dB below the peak power
1.3.2 If this guide method is used at sites with hazardous
radiatedfromtheantennaatitsresonantfrequency.Sometimes
materials, operations, or equipment, it is the responsibility of
the ratio of the upper and lower 3-dB frequencies is used to
the user of this guide to establish appropriate safety and health
describeanantenna’sbandwidth.Forexample,iftheupperand
practices and to determine the applicability of any regulations
lower 3-dB frequencies of an antenna are 600 and 200 MHz,
prior to use.
respectively, the bandwidth of the antenna is said to be 3:1. In
1.3.3 This guide does not purport to address all of the safety
GPR system design, the ratio of the difference between the
concerns that may be associated with the use of the GPR
upper frequency minus the lower frequency to the center
method. It is the responsibility of the user of this guide to
frequencyiscommonlyused.Intheprecedingcase,onewould
establish appropriate safety and health practices and to
have a ratio of 400:400 or 1:1.
determine the applicability of regulations prior to use.
3.1.3.4 bistatic—the survey method that utilizes antennas.
One antenna radiates the EM waves and the other antenna
2. Referenced Documents
receives the reflected waves.
2.1 ASTM Standards:
3.1.3.5 conductivity—the ability of a material to support an
D420 Guide to Site Characterization for Engineering De-
electrical current (material property that describes the move-
sign and Construction Purposes
mentofelectronsorions)duetoanappliedelectricalfield.The
D653 Terminology Relating to Soil, Rock, and Contained
units of conductivity are Siemens/metre (S/m).
Fluids
3.1.3.6 control unit (C/U)—An electronic instrument that
D5730 Guide for Site Characterization for Environmental
controls GPR data collection. The control unit may also
Purposes With Emphasis on Soil, Rock, the Vadose Zone
process, display, and store the GPR data.
and Ground Water
3.1.3.7 coupling—the coupling of a ground penetrating
D5753 Guide for Planning and Conducting Borehole Geo-
radarantennatothegrounddescribestheabilityoftheantenna
physical Logging
to get electromagnetic energy into the ground. A poorly
D6235 Practice for Expedited Site Characterization of Va-
doseZoneandGroundWaterContaminationatHazardous coupled antenna is described as being mismatched. A well-
coupled antenna has an impedance equal to the impedance of
Waste Contaminated Sites
D6429 Guide for Selecting Surface Geophysical Methods the ground.
3.1.3.8 depth of penetration—the maximum depth range a
3. Terminology
radar signal can penetrate in a given medium, be scattered by
3.1 Definitions: an electrical inhomogeneity, propagate back to the surface, be
3.1.1 Definitions shall be in accordance with the terms and recorded by a receiver GPR antenna, and yield a voltage
symbols given in Terminology D653. greater than the noise levels of the GPR unit.
3.1.2 The majority of the technical terms used in this guide
(1) In a conductive material (seawater, metallic materials, or
are defined in Sheriff (27).
mineralogic clay soils), attenuation can be great, and the wave
3.1.3 Additional Definitions:
may penetrate only a short distance (less than 1 m). In a
3.1.3.1 antenna—a transmitting GPR antenna converts an
resistive material (fresh water, granite, ice, or quartz sand), the
excitationintheformofavoltagepulseorwavetrainintoEM
depth of penetration can be tens to thousands of metres.
waves.Areceiving GPR antenna converts energy contained in
3.1.3.9 dielectric permittivity—dielectric permittivity is the
EM waves into voltages, which are regarded as GPR data.
propertythatdescribestheabilityofamaterialtostoreelectric
3.1.3.2 attenuation—(1) the loss of EM wave energy due to
energy by separating opposite polarity charges in space. It
conduction currents associated with finite conductivity (s) and
relates ability of a material to be polarized in the electric
the dielectric relaxation (also referred to as polarization loss)
displacement, D, in response to the application of an electric
associated with the imaginary component of the permittivity
field, E, through D=´ E.The units of dielectric permittivity, ´,
(´9), and magnetic relaxation associated with the imaginary
are farads/metre (F/m). Relative dielectric permittivity (previ-
component of magnetic permeability.
ously called the dielectric constant) is the ratio of the permit-
(2)Theterm“attenuation”isalsosometimesusedtoreferto
−12
tivity of a material to that of free space, 8.854 3 10 F/m.
the loss in EM wave energy from all possible sources,
Wheneverthedielectricpermittivityisgreaterthanthatoffree
space, it must be complex and lossy, with frequency depen-
dence typically described by the Cole-Cole (Cole and Cole
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
(28)) relaxation distribution model. Nearly all dielectric relax-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ation processes are the result of the presence of water or clay
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. minerals (Olhoeft (29)).
D6432 – 99 (2005)
3.1.3.10 dielectric relaxation—generally used to describe 3.1.3.16 megahertz (MHz)—aunitoffrequency.Onemega-
EM wave attenuation due to ´9 (the imaginary part of the hertz equals 10 Hz.
complex permittivity). The term is derived from the empirical
3.1.3.17 monostatic—(1) a survey method that utilizes a
relationship developed by describing the frequency-dependent
single antenna acting as both the transmitter and receiver of
behavior of dielectrics. The classical Debye formulation con-
EM waves. (2) Two antennas, one transmitting and one
tains a term referred to as the relaxation time.
receiving, that are separated by a small distance relative to the
depth of interest are sometimes referred to as operating in
3.1.3.11 diffusion—the process by which the application of
“monostatic mode.”
an external force (stimulus) results in a flux or movement of
something (response). In electromagnetics, diffusion describes 3.1.3.18 nanosecond (Ns)—aunitoftime.Onenanosecond
−9
themovementofchargesinresponsetoanappliedelectricfield equals 10 s; one billionth of a second.
or in response to an applied time-varying magnetic field.
3.1.3.19 polarization—(1) the storage of electrical or mag-
Diffusion is the low-frequency, high-loss, limiting behavior of
netic energy by the application of electric or magnetic fields to
electromagnetic wave propagation and is descriptive of behav-
matter. (2) The orientation of the direction of the vector
ior that decays rapidly (exponentially) with distance and time,
electromagnetic field is described by the polarization vector.
generallyto1/eoftheinitialamplitudein ⁄2 pofawavelength.
Most GPR antennas are linearly polarized, though some are
circularly polarized (Balanis (27)).
3.1.3.12 dipole antenna—a linear polarization antenna con-
sisting of two wires fed at the middle by a balanced source 3.1.3.20 propagation—when sufficient energy storage is
(Balanis (27)). available compared to energy dissipation (loss) processes in a
material, electromagnetic waves may propagate instead of
3.1.3.13 Fresnel zone—the area of a target’s surface that
exponential rapid decay (diffusion). Propagation is character-
contains the portion of the incident wave that arrives at the
1 ized by a decay in amplitude from the source to 1/e in several
receive antenna less than ⁄2 of a cycle out-of-phase from
wavelengths, a distance called the skin depth or attenuation
earliest arriving reflected energy from the target. There are
length.
multiple Fresnel zones that form annular rings around the first
3.1.3.21 receiver—the electronics that are connected to
Fresnel zone (Sheriff (26)).
antenna that is excited by EM waves and converts the EM
3.1.3.14 loss tangent—There are three loss tangents: elec-
energy into voltages.
tric, magnetic, and electromagnetic. Each loss tangent is the
3.1.3.22 relative permittivity (relative dielectric permittiv-
ratio of the imaginary to the real parts or the lossy to the
ity; sometimes called Dielectric constant)—property of an
storage parts of the response to the stimulus in the force-flux
electrical insulating material equal to the ratio of the capaci-
stimulus-response equations. The electrical loss tangent is the
tance of a capacitor filled with a given material to the
ratio of the imaginary to the real part of the dielectric
capacitance of the identical capacitor filled with air. Earth
permittivity plus the electrical conductivity divided by radian
materials are classified generally as conductors, semiconduc-
frequency times the real part of the permittivity. It represents
tors,andinsulators(dielectrics).Therelativepermittivityisthe
the cotangent of the phase between E and J (el
...
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