ASTM D7006-03(2022)
(Practice)Standard Practice for Ultrasonic Testing of Geomembranes
Standard Practice for Ultrasonic Testing of Geomembranes
SIGNIFICANCE AND USE
5.1 This practice covers test arrangements, measurement techniques, sampling methods, and calculations to be used for nondestructive evaluation of geomembranes using ultrasonic testing.
5.2 Wave velocity may be established for particular geomembranes (for specific polymer type, specific formulation, specific density). Relationships may be established between velocity and both density and tensile properties of geomembranes. An example of the use of ultrasound for determining density of polyethylene is presented in Test Method D4883. Velocity measurements may be used to determine thickness of geomembranes (1, 2).4 Travel time and amplitude of transmitted waves may be used to assess the condition of geomembranes and to identify defects in geomembranes including surface defects (for example, scratches, cuts), inner defects (for example, discontinuities within geomembranes), and defects that penetrate the entire thickness of geomembranes (for example, pinholes) (3, 4). Bonding between geomembrane sheets can be evaluated using travel time, velocity, or impedance measurements for seam assessment (5-10). Examples of the use of ultrasonic testing for determining the integrity of field and factory seams through travel time and velocity measurements (resulting in thickness measurements) are presented in Practices D4437 and D4545, respectively. An ultrasonic testing device is routinely used for evaluating seams in prefabricated bituminous geomembranes in the field (11). Integrity of geomembranes may be monitored in time using ultrasonic measurements.
Note 1: Differences may exist between ultrasonic measurements and measurements made using other methods due to differences in test conditions such as pressure applied and probe dimensions. An example is ultrasonic and mechanical thickness measurements.
5.3 The method is applicable to testing both in the laboratory and in the field for parent material and seams. The test durations are very short as wave transmission through ...
SCOPE
1.1 This practice provides a summary of equipment and procedures for ultrasonic testing of geomembranes using the pulse echo method.
1.2 Ultrasonic wave propagation in solid materials is correlated to physical and mechanical properties and condition of the materials. In ultrasonic testing, two wave propagation characteristics are commonly determined: velocity (based on wave travel time measurements) and attenuation (based on wave amplitude measurements). Velocity of wave propagation is used to determine thickness, density, and elastic properties of materials. Attenuation of waves in solid materials is used to determine microstructural properties of the materials. In addition, frequency characteristics of waves are analyzed to investigate the properties of a test material. Travel time, amplitude, and frequency distribution measurements are used to assess the condition of materials to identify damage and defects in solid materials. Ultrasonic measurements are used to determine the nature of materials/media in contact with a test specimen as well. Measurements are conducted in the time-domain (time versus amplitude) or frequency-domain (frequency versus amplitude).
1.3 Measurements of one or more ultrasonic wave transmission characteristics are made based on the requirements of the specific testing program.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development ...
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Designation: D7006 − 03 (Reapproved 2022)
Standard Practice for
Ultrasonic Testing of Geomembranes
This standard is issued under the fixed designation D7006; 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 mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This practice provides a summary of equipment and
procedures for ultrasonic testing of geomembranes using the
2. Referenced Documents
pulse echo method.
2.1 ASTM Standards:
1.2 Ultrasonic wave propagation in solid materials is corre-
D4437 Practice for Nondestructive Testing (NDT) for De-
lated to physical and mechanical properties and condition of
termining the Integrity of Seams Used in Joining Flexible
the materials. In ultrasonic testing, two wave propagation
Polymeric Sheet Geomembranes
characteristics are commonly determined: velocity (based on
D4545 Practice for Determining the Integrity of Factory
wave travel time measurements) and attenuation (based on
Seams Used in Joining Manufactured Flexible Sheet
wave amplitude measurements). Velocity of wave propagation 3
Geomembranes (Withdrawn 2008)
isusedtodeterminethickness,density,andelasticpropertiesof
D4883 Test Method for Density of Polyethylene by the
materials. Attenuation of waves in solid materials is used to
Ultrasound Technique
determine microstructural properties of the materials. In
E1316 Terminology for Nondestructive Examinations
addition, frequency characteristics of waves are analyzed to
investigate the properties of a test material. Travel time,
3. Terminology
amplitude, and frequency distribution measurements are used
3.1 Definitions:
to assess the condition of materials to identify damage and
3.1.1 atmosphere for testing geomembranes, n—air main-
defects in solid materials. Ultrasonic measurements are used to
tained at a relative humidity of 50 to 70 % and a temperature
determine the nature of materials/media in contact with a test
of 21 6 1 °C.
specimen as well. Measurements are conducted in the time-
3.1.2 geomembrane,n—anessentiallyimpermeablegeosyn-
domain (time versus amplitude) or frequency-domain (fre-
thetic composed of one or more synthetic sheets.
quency versus amplitude).
3.1.3 For definitions of terms related to ultrasonic testing,
1.3 Measurements of one or more ultrasonic wave transmis-
refer to Terminology E1316.
sion characteristics are made based on the requirements of the
specific testing program.
4. Summary of Practice
1.4 The values stated in SI units are to be regarded as
4.1 Mechanical waves are introduced to a geomembrane
standard. No other units of measurement are included in this
from a surface of the material using an ultrasonic transducer.
standard.
Transmission characteristics of the waves in the geomembrane
1.5 This standard does not purport to address all of the
are determined. The measured characteristics are used to
safety concerns, if any, associated with its use. It is the
evaluate certain properties and conditions of geomembranes.
responsibility of the user of this standard to establish appro-
5. Significance and Use
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
5.1 This practice covers test arrangements, measurement
1.6 This international standard was developed in accor-
techniques, sampling methods, and calculations to be used for
dance with internationally recognized principles on standard-
nondestructive evaluation of geomembranes using ultrasonic
ization established in the Decision on Principles for the
testing.
Development of International Standards, Guides and Recom-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This practice is under the jurisdiction of ASTM Committee D35 on Geosyn- contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
thetics and is the direct responsibility of Subcommittee D35.10 on Geomembranes. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Jan. 15, 2022. Published January 2022. Originally the ASTM website.
approved in 2003. Last previous edition approved in 2013 as D7006 – 03 (2013). The last approved version of this historical standard is referenced on
DOI: 10.1520/D7006-03R22. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7006 − 03 (2022)
conditions such as pressure applied and probe dimensions.An example is
5.2 Wave velocity may be established for particular
ultrasonic and mechanical thickness measurements.
geomembranes (for specific polymer type, specific
formulation, specific density). Relationships may be estab-
5.3 The method is applicable to testing both in the labora-
lished between velocity and both density and tensile properties
tory and in the field for parent material and seams. The test
of geomembranes. An example of the use of ultrasound for
durations are very short as wave transmission through
determining density of polyethylene is presented in Test
geomembranes occurs within microseconds.
Method D4883. Velocity measurements may be used to deter-
mine thickness of geomembranes (1, 2). Travel time and
6. Apparatus
amplitude of transmitted waves may be used to assess the
6.1 The test equipment consists of a single transducer (both
conditionofgeomembranesandtoidentifydefectsingeomem-
transmitter and receiver); a pulse generator; a pulse receiver
branes including surface defects (for example, scratches, cuts),
(includes amplifier and filters for noise reduction); electronic
inner defects (for example, discontinuities within
circuits to measure and record waveforms, to measure wave
geomembranes), and defects that penetrate the entire thickness
travel time, to measure wave amplitudes, and to display
of geomembranes (for example, pinholes) (3, 4). Bonding
received signals; electronic circuitry to time and synchronize
between geomembrane sheets can be evaluated using travel
all instrument functions; and connecting cables. The test
time, velocity, or impedance measurements for seam assess-
apparatus is shown in Fig. 1.
ment (5-10). Examples of the use of ultrasonic testing for
determining the integrity of field and factory seams through
6.2 Piezoelectric transducers are effective for wave trans-
travel time and velocity measurements (resulting in thickness
mission. Compressional waves (P-waves, longitudinal waves)
measurements) are presented in Practices D4437 and D4545,
shall be used for ultrasonic testing of geomembranes.Aspacer
respectively. An ultrasonic testing device is routinely used for
shall be used to obtain good near surface resolution and to
evaluating seams in prefabricated bituminous geomembranes
eliminate near field effects for accurate measurement of ultra-
in the field (11). Integrity of geomembranes may be monitored
sonic wave propagation characteristics in geomembranes. A
in time using ultrasonic measurements.
plastic spacer has been found to be effective for geomem-
NOTE 1—Differences may exist between ultrasonic measurements and
branes. The thickness of the spacer shall be at least twice the
measurements made using other methods due to differences in test
thicknessofthetestspecimen.Thethicknessofthespacershall
be less than five to ten times the thickness of the test
geomembrane. For testing geomembranes with various
The boldface numbers in parentheses refer to the list of references at the end of
thicknesses, use the material with the largest thickness for
this standard.
FIG. 1 Test Apparatus
D7006 − 03 (2022)
edge measurements shall be demonstrated prior to their routine use to
selection of the thickness of the spacer. The spacer shall be
ensure that potential edge reflections do not interfere with measurements
sufficiently large to cover the active surface area of the
through the thickness of geomembranes.
transducer to ensure that the waveform generated is fully
transmitted to the test specimen through the spacer. The center
9. Calibration
frequency of the transducer shall be between 1 and 20 MHz (a
9.1 The electronic equipment shall be calibrated to ensure
10 MHz transducer has been found to be effective). Focused
accurate determination of the transit time. Calibration bars or
transducers shall be used for textured geomembranes to ensure
blocks with known thicknesses and wave transmission veloci-
measurements are made over essentially a “point” on the test
ties shall be used for calibration procedures.
material. Other means may also be used if high-frequency
mechanical waves can be generated with these devices.
10. Conditioning
6.3 Pulsegeneratorshallgeneratepulsesofelectricalenergy
10.1 For baseline measurements (for example, measure-
that activate the transducer. Pulsers that generate spike or
ments used to establish baseline ultrasonic properties for a
square wave type voltage pulses have been found to be
particular geomembrane), specimens shall be exposed to the
effective for testing geomembranes.
standard atmosphere for testing geomembranes for a period
sufficient to reach moisture and temperature equilibrium.
6.4 The receiver shall amplify and filter the signal received
Exposure for 24 h has been found to be effective for reaching
by the transducer after the waves have been transmitted
equilibrium.
through a test sample.
10.2 Tests can be conducted at conditions outside the range
6.5 Electronic circuitry shall be used to measure travel time
for standard atmosphere conditions for various applications
of waves in a test sample. The circuitry shall allow for
such as field measurements. For these measurements, speci-
determination of travel times with a precision equal to or better
mens shall be in moisture and temperature equilibrium with
than 0.1 µs. If attenuation and amplitude measurements are
their surrounding environment.
desired, instrumentation shall be used to record the waveforms
NOTE4—Correctionfactorsshallbeusedifcomparisonsaretobemade
received from a test material. The circuitry shall allow for
between standard and nonstandard testing conditions. Correction factors
determination of amplitudes with a precision equal to or better
are determined by taking measurements at nonstandard conditions and
than 1 mV. Electronic circuitry may also be used to display
normalizing these by the measurements conducted at standard conditions.
received signals. Analog to digital converters and computer-
10.3 Surface Preparation—The surface of the test geomem-
ized signal acquisition and analysis setups have been found to
brane shall be free of excessive dust, particles, and any other
be effective for testing geomembranes.
materials that may interfere with wave transmission. The
6.6 Electronic circuitry shall be used to time and synchro-
surface of geomembranes may be cleaned with a damp cloth to
nize all instrument functions to eliminate uncertainty in the
ensure a clean measurement surface prior to testing.
determination of wave transit times.
11. Procedure
NOTE 2—The apparatus listed here has been found to be effective for
testing geomembranes. Ultrasonic testing of materials is a well-
11.1 Ultrasonic measurements in geomembranes shall be
established field and other types of devices may also be used for testing
conducted using the pulse echo test method. In this method,
geomembranes. Details for various test arrangements and examples of
ultrasonic waves are sent and received from one surface of a
devices produced by various manufacturers are available in (12). Effec-
tiveness of alternative devices shall be demonstrated prior to their routine
testspecimenusingoneortwotransducers.Asingletransducer
use for geomembranes.
shall be used in the measurements of geomembranes.
11.2 Ultrasonic measurements on geomembranes may be
7. Materials
taken using two test arrangements. In both arrangements, the
7.1 A coupling agent shall be used to ensure good contact
transducer shall be orthogonal to the test geomembrane.
between the transducer and test specimen. Coupling agents
11.2.1 Arrangement A—In this arrangement the transducer
include water, commercial ultrasonic couplants, oil, petroleum
assembly is placed over the test geomembrane. The transducer
jelly,grease,glycerin,propyleneglycol,orotherviscousfluids.
assembly consists of the ultrasonic transducer and the spacer.
Water has been used effectively on flat surfaces. More viscous
Apply a small amount of couplant between the transducer and
materials may be used on inclined surfaces.
the spacer to ensure that the two units are in good contact with
no air gaps. Then, apply a small amount of couplant on the
8. Sampling and Test Specimens
surface of the geomembrane at the measurement location.
8.1 Test specimens shall be cut such that a distance greater
Place the transducer assembly on the geomembrane, leaving a
than ten times the thickness of the specimen shall be left
thin film of couplant between the assembly and the geomem-
between the transducer and the edges of the specimen in every
brane. Ensure that the transducer assembly is in good contact
direction.
(for example, no air gaps) with the geomembrane.Asmall load
may be permanently attached on top of the transducer to
8.2 In field testing, measurements shall be taken at locations
provide good contact with the geomembrane and ensure that
that are at a distance greater than ten times the thickness of the
thetransducerisperfectlyorthogonaltothetestspecimen.This
specimen from the edges of the geomembrane sheet in any
arrangement is presented in Fig. 2(a).
direction.
11.2.2 Arrangement B—In this arrangement the transducer
NOTE 3—Seam inspection tests may be conducted at locations closer to
the edge of geomembranes than specified in 8.2. Effectiveness of the near assembly is placed below the test geomembrane.Apply a small
D7006 − 03 (2022)
FIG. 2 Test Arrangements
theultrasonicunits.Useofthesetypesoftransducershasbeenfoundtobe
amount of couplant between the transducer and the spacer to
effective for testing geomembranes. Commercially available immersion
ensure that the two units are in good contact with no air gaps.
transducer setups can be used in Test Arrangement B. In these setups a
Then, apply a small amount of couplant on the top surface of
water-resistant transducer is placed at a certain depth in a water bath. The
the spacer. Place the geomembrane over the spacer, leaving a
specimen is placed directly on the
...
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: D7006 − 03 (Reapproved 2013) D7006 − 03 (Reapproved 2022)
Standard Practice for
Ultrasonic Testing of Geomembranes
This standard is issued under the fixed designation D7006; 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
1.1 This practice provides a summary of equipment and procedures for ultrasonic testing of geomembranes using the pulse echo
method.
1.2 Ultrasonic wave propagation in solid materials is correlated to physical and mechanical properties and condition of the
materials. In ultrasonic testing, two wave propagation characteristics are commonly determined: velocity (based on wave travel
time measurements) and attenuation (based on wave amplitude measurements). Velocity of wave propagation is used to determine
thickness, density, and elastic properties of materials. Attenuation of waves in solid materials is used to determine microstructural
properties of the materials. In addition, frequency characteristics of waves are analyzed to investigate the properties of a test
material. Travel time, amplitude, and frequency distribution measurements are used to assess the condition of materials to identify
damage and defects in solid materials. Ultrasonic measurements are used to determine the nature of materials/media in contact with
a test specimen as well. Measurements are conducted in the time-domain (time versus amplitude) or frequency-domain (frequency
versus amplitude).
1.3 Measurements of one or more ultrasonic wave transmission characteristics are made based on the requirements of the specific
testing program.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
D4437 Practice for Nondestructive Testing (NDT) for Determining the Integrity of Seams Used in Joining Flexible Polymeric
Sheet Geomembranes
This practice is under the jurisdiction of ASTM Committee D35 on Geosynthetics and is the direct responsibility of Subcommittee D35.10 on Geomembranes.
Current edition approved May 1, 2013Jan. 15, 2022. Published May 2013January 2022. Originally approved in 2003. Last previous edition approved in 20082013 as
D7006–03(2008).D7006 – 03 (2013). DOI: 10.1520/D7006-03R13.10.1520/D7006-03R22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7006 − 03 (2022)
D4545 Practice for Determining the Integrity of Factory Seams Used in Joining Manufactured Flexible Sheet Geomembranes
(Withdrawn 2008)
D4883 Test Method for Density of Polyethylene by the Ultrasound Technique
E1316 Terminology for Nondestructive Examinations
3. Terminology
3.1 Definitions:
3.1.1 atmosphere for testing geomembranes, n—air maintained at a relative humidity of 50 to 70 % and a temperature of 21 6
1°C.1 °C.
3.1.2 geomembrane, n—an essentially impermeable geosynthetic composed of one or more synthetic sheets.
3.1.3 For definitions of terms related to ultrasonic testing, refer to Terminology E1316.
4. Summary of Practice
4.1 Mechanical waves are introduced to a geomembrane from a surface of the material using an ultrasonic transducer.
Transmission characteristics of the waves in the geomembrane are determined. The measured characteristics are used to evaluate
certain properties and conditionconditions of geomembranes.
5. Significance and Use
5.1 This practice covers test arrangements, measurement techniques, sampling methods, and calculations to be used for
nondestructive evaluation of geomembranes using ultrasonic testing.
5.2 Wave velocity may be established for particular geomembranes (for specific polymer type, specific formulation, specific
density). Relationships may be established between velocity and both density and tensile properties of geomembranes. An example
of the use of ultrasound for determining density of polyethylene is presented in Test Method D4883. Velocity measurements may
be used to determine thickness of geomembranes (1, 2). Travel time and amplitude of transmitted waves may be used to assess
the condition of geomembranes and to identify defects in geomembranes including surface defects (for example, scratches, cuts),
inner defects (for example, discontinuities within geomembranes), and defects that penetrate the entire thickness of geomembranes
(for example, pinholes) (3, 4). Bonding between geomembrane sheets can be evaluated using travel time, velocity, or impedance
measurements for seam assessment (5-10). Examples of the use of ultrasonic testing for determining the integrity of field and
factory seams through travel time and velocity measurements (resulting in thickness measurements) are presented in Practices
D4437 and D4545, respectively. An ultrasonic testing device is routinely used for evaluating seams in prefabricated bituminous
geomembranes in the field (11). Integrity of geomembranes may be monitored in time using ultrasonic measurements.
NOTE 1—Differences may exist between ultrasonic measurements and measurements made using other methods due to differences in test conditions such
as pressure applied and probe dimensions. An example is ultrasonic and mechanical thickness measurements.
5.3 The method is applicable to testing both in the laboratory and in the field for parent material and seams. The test durations
are very short as wave transmission through geomembranes occurs within microseconds.
6. Apparatus
6.1 The test equipment consists of a single transducer (both transmitter and receiver); a pulse generator; a pulse receiver (includes
amplifier and filters for noise reduction); electronic circuits to measure and record waveforms, to measure wave travel time, to
measure wave amplitudes, and to display received signals; electronic circuitry to time and synchronize all instrument functions;
and connecting cables. The test apparatus is shown in Fig. 1.
6.2 Piezoelectric transducers are effective for wave transmission. Compressional waves (P-waves, longitudinal waves) shall be
used for ultrasonic testing of geomembranes. A spacer shall be used to obtain good near surface resolution and to eliminate near
field effects for accurate measurement of ultrasonic wave propagation characteristics in geomembranes. A plastic spacer has been
The last approved version of this historical standard is referenced on www.astm.org.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
D7006 − 03 (2022)
FIG. 1 Test Apparatus
found to be effective for geomembranes. The thickness of the spacer shall be at least twice the thickness of the test specimen. The
thickness of the spacer shall be less than 5five to 10ten times the thickness of the test geomembrane. For testing geomembranes
with various thicknesses, use the material with the largest thickness for selection of the thickness of the spacer. The spacer shall
be sufficiently large to cover the active surface area of the transducer to ensure that the waveform generated is fully transmitted
to the test specimen through the spacer. The center frequency of the transducer shall be between 1 and 20 MHz (a 10 MHz
transducer has been found to be effective). Focused transducers shall be used for textured geomembranes to ensure measurements
are made over essentially a “point” on the test material. Other means may also be used if high frequency high-frequency
mechanical waves can be generated with these devices.
6.3 Pulse generator shall generate pulses of electrical energy that activate the transducer. Pulsers that generate spike or square
wave type voltage pulses have been found to be effective for testing geomembranes.
6.4 The receiver shall amplify and filter the signal received by the transducer after the waves have been transmitted through a test
sample.
6.5 Electronic circuitry shall be used to measure travel time of waves in a test sample. The circuitry shall allow for determination
of travel times with a precision equal to or better than 0.1 μs. If attenuation and amplitude measurements are desired,
instrumentation shall be used to record the waveforms received from a test material. The circuitry shall allow for determination
of amplitudes with a precision equal to or better than 1 mV. Electronic circuitry may also be used to display received signals.
Analog to digital converters and computerized signal acquisition and analysis setups have been found to be effective for testing
geomembranes.
6.6 Electronic circuitry shall be used to time and synchronize all instrument functions to eliminate uncertainty in the determination
of wave transit times.
NOTE 2—The apparatus listed here has been found to be effective for testing geomembranes. Ultrasonic testing of materials is a well established
well-established field and other types of devices may also be used for testing geomembranes. Details for various test arrangements and examples of
D7006 − 03 (2022)
devices produced by various manufacturers are available in (12). Effectiveness of alternative devices shall be demonstrated prior to their routine use for
geomembranes.
7. Materials
7.1 A coupling agent shall be used to ensure good contact between the transducer and test specimen. Coupling agents include
water, commercial ultrasonic couplants, oil, petroleum jelly, grease, glycerin, propylene glycol, or other viscous fluids. Water has
been used effectively on flat surfaces. More viscous materials may be used on inclined surfaces.
8. Sampling and Test Specimens
8.1 Test specimens shall be cut such that a distance greater than 10ten times the thickness of the specimen shall be left between
the transducer and the edges of the specimen in every direction.
8.2 In field testing, measurements shall be taken at locations that are at a distance greater than 10ten times the thickness of the
specimen from the edges of the geomembrane sheet in any direction.
NOTE 3—Seam inspection tests may be conducted at locations closer to the edge of geomembranes than specified in 8.2. Effectiveness of the near edge
measurements shall be demonstrated prior to their routine use to ensure that potential edge reflections do not interfere with measurements through the
thickness of geomembranes.
9. Calibration
9.1 The electronic equipment shall be calibrated to ensure accurate determination of the transit time. Calibration bars or blocks
with known thicknesses and wave transmission velocities shall be used for calibration procedures.
10. Conditioning
10.1 For baseline measurements (for example, measurements used to establish baseline ultrasonic properties for a particular
geomembrane), specimens shall be exposed to the standard atmosphere for testing geomembranes for a period sufficient to reach
moisture and temperature equilibrium. Exposure for 24 h has been found to be effective for reaching equilibrium.
10.2 Tests can be conducted at conditions outside the range for standard atmosphere conditions for various applications such as
field measurements. For these measurements, specimens shall be in moisture and temperature equilibrium with their surrounding
environment.
NOTE 4—Correction factors shall be used if comparisons are to be made between standard and nonstandard testing conditions. Correction factors are
determined by taking measurements at nonstandard conditions and normalizing these by the measurements conducted at standard conditions.
10.3 Surface Preparation—The surface of the test geomembrane shall be free of excessive dust, particles, and any other materials
that may interfere with wave transmission. The surface of geomembranes may be cleaned with a damp cloth to ensure a clean
measurement surface prior to testing.
11. Procedure
11.1 Ultrasonic measurements in geomembranes shall be conducted using the pulse echo test method. In this method, ultrasonic
waves are sent and received from one surface of a test specimen using one or two transducers. A single transducer shall be used
in the measurements of geomembranes.
11.2 Ultrasonic measurements on geomembranes may be taken using two test arrangements. In both arrangements, the transducer
shall be orthogonal to the test geomembrane.
11.2.1 Arrangement A—In this arrangement the transducer assembly is placed over the test geomembrane. The transducer
assembly consists of the ultrasonic transducer and the spacer. Apply a small amount of couplant between the transducer and the
spacer to ensure that the two units are in good contact with no air gaps. Then, apply a small amount of couplant on the surface
of the geomembrane at the measurement location. Place the transducer assembly on the geomembrane, leaving a thin film of
couplant between the assembly and the geomembrane. Ensure that the transducer assembly is in good contact (for example, no air
D7006 − 03 (2022)
gaps) with the geomembrane. A small load may be permanently attached on top of the transducer to provide good contact with
the geomembrane and ensure that the transducer is perfectly orthogonal to the test specimen. This arrangement is presented in Fig.
2a. (a).
11.2.2 Arrangement B—In this arrangement the transducer assembly is placed below the test geomembrane. Apply a small amount
of couplant between the transducer and the sp
...
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