ASTM D6760-16
(Test Method)Standard Test Method for Integrity Testing of Concrete Deep Foundations by Ultrasonic Crosshole Testing
Standard Test Method for Integrity Testing of Concrete Deep Foundations by Ultrasonic Crosshole Testing
SIGNIFICANCE AND USE
5.1 This method uses data from ultrasonic probes lowered into parallel access ducts, or in a single access duct, in the deep foundation element to assess the homogeneity and integrity of concrete between the probes. The data are used to confirm adequate concrete quality or identify zones of poor quality. If defects are detected, then further investigations should be made by excavation or coring the concrete as appropriate, or by other testing such as Test Method D1143, D4945 or D5882, and measures taken to remediate the structure if a defect is confirmed.
5.2 Limitations:
5.2.1 For crosshole tests, the access ducts should preferably be made of steel to prevent debonding of the access duct from the concrete resulting in an anomaly. This test can assess to the integrity of the concrete mainly in the area bounded by the access ducts, which means typically inside the reinforcement cage.
5.2.2 For single hole tests the access tubes must be plastic tubes. Testing should therefore be performed as soon as practical in order to avoid debonding issues. Since the generated waves travel through the concrete around the access duct, unless a flaw is massive enough and very near to the access duct it may not be detected by this method.
Note 1: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing and inspection. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
SCOPE
1.1 This test method covers procedures for checking the homogeneity and integrity of concrete in deep foundation such as bored piles, drilled shafts, concrete piles or augercast piles. This method can also be extended to diaphragm walls, barrettes, dams etc. In this test method, all the above will be designated “deep foundation elements.” The test measures the propagation time and relative energy of an ultrasonic pulse between parallel access ducts (crosshole) or in a single tube (single hole) installed in the deep foundation element. This method is most applicable when performed in tubes that are installed during construction.
1.2 Similar techniques with different excitation sources exist, but these techniques are outside the scope of this test method.
1.3 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.
1.4 The method used to specify how data are collected, calculated, or recorded in this test method is not directly related to the accuracy to which data can be applied in design or other uses, or both. How one applies the results obtained using this standard is beyond its scope.
1.5 This standard provides minimum requirements for crosshole (or single hole) testing of concrete deep foundation elements. Plans, specifications, provisions, or combinations thereof prepared by a qualified engineer, and approved by the agency requiring the test(s), may provide additional requirements and procedures as needed to satisfy the objectives of a particular test program.
1.6 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.8 Limitations—Proper installation of the access ducts is essential for effective testing and interpretation. The method does not give the exact type of flaw (for example, inclusion, honeycombing, lack of cement particles, etc....
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: D6760 − 16
Standard Test Method for
Integrity Testing of Concrete Deep Foundations by
Ultrasonic Crosshole Testing
This standard is issued under the fixed designation D6760; 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 1.7 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
1.1 This test method covers procedures for checking the
standard.
homogeneity and integrity of concrete in deep foundation such
1.8 Limitations—Proper installation of the access ducts is
as bored piles, drilled shafts, concrete piles or augercast piles.
essential for effective testing and interpretation. The method
This method can also be extended to diaphragm walls,
does not give the exact type of flaw (for example, inclusion,
barrettes, dams etc. In this test method, all the above will be
designated “deep foundation elements.” The test measures the honeycombing, lack of cement particles, etc.) but rather only
that a flaw exists.
propagation time and relative energy of an ultrasonic pulse
between parallel access ducts (crosshole) or in a single tube
1.9 This standard does not purport to address all of the
(single hole) installed in the deep foundation element. This
safety concerns, if any, associated with its use. It is the
method is most applicable when performed in tubes that are
responsibility of the user of this standard to establish appro-
installed during construction.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.2 Similar techniques with different excitation sources
exist, but these techniques are outside the scope of this test
2. Referenced Documents
method.
2.1 ASTM Standards:
1.3 All observed and calculated values shall conform to the
D653 Terminology Relating to Soil, Rock, and Contained
guidelines for significant digits and rounding established in
Fluids
Practice D6026.
D1143 Test Method for Piles Under Static Axial Compres-
1.4 The method used to specify how data are collected,
sive Load (Withdrawn 2005)
calculated,orrecordedinthistestmethodisnotdirectlyrelated
D3740 Practice for Minimum Requirements for Agencies
to the accuracy to which data can be applied in design or other Engaged in Testing and/or Inspection of Soil and Rock as
uses, or both. How one applies the results obtained using this
Used in Engineering Design and Construction
standard is beyond its scope. D4945 Test Method for High-Strain Dynamic Testing of
Deep Foundations
1.5 This standard provides minimum requirements for
D5882 Test Method for Low Strain Impact Integrity Testing
crosshole (or single hole) testing of concrete deep foundation
of Deep Foundations
elements. Plans, specifications, provisions, or combinations
D6026 Practice for Using Significant Digits in Geotechnical
thereof prepared by a qualified engineer, and approved by the
Data
agency requiring the test(s), may provide additional require-
ments and procedures as needed to satisfy the objectives of a
3. Terminology
particular test program.
3.1 Definitions of Terms Specific to This Standard:
1.6 The text of this standard references notes and footnotes
3.1.1 access ducts, n—preformed steel tubes, plastic tubes
which provide explanatory material. These notes and footnotes
(for example, PVC or equivalent), or drilled boreholes, placed
(excluding those in tables and figures) shall not be considered
in the concrete to allow probe entry in pairs to measure pulse
as requirements of the standard.
transmission in the concrete between the probes.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
RockandisthedirectresponsibilityofSubcommitteeD18.11onDeepFoundations. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Dec. 1, 2016. Published January 2017. Originally the ASTM website.
approved in 2002. Last previous edition approved in 2014 as D6760 – 14. DOI: The last approved version of this historical standard is referenced on
10.1520/D6760-16. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6760 − 16
3.1.2 anomaly, n—irregularity or series of irregularities multiple access ducts can also be allowed. Testing of the
observed in an ultrasonic profile indicating a possible flaw. concrete in the vicinity of the access duct can also be made
with both probes installed in a single access duct.
3.1.3 defect, n—a flaw that, because of either size or
location, may significantly detract from the element’s capacity
4.2 Two ultrasonic probes, one a transmitter and the other a
or durability.
receiver, are lowered to the bottom of their respective water-
filled access duct(s) to test the full shaft length from bottom to
3.1.4 depth interval, n—the maximum incremental spacing
top. The transmitter probe generates ultrasonic pulses at
along the pile shaft between ultrasonic pulses.
frequent and regular intervals during the probes’ controlled
3.1.5 flaw, n—any deviation from the planned shape or
travel rate. The probe depth and receiver probe’s output (timed
material (or both) of the element.
relative to the transmitter probe’s ultrasonic pulse generation)
3.1.6 integrity evaluation, n—the qualitative or quantitative
are recorded for each pulse. The receiver’s output signals are
evaluation of the concrete continuity and consistency between
sampled and saved as voltage versus time (see Fig. 1) for each
the access ducts or boreholes.
sampled depth. These signals can be then nested to produce a
3.1.7 ultrasonic profile, n—a combined graphical output of
“waterfall” diagram (see right side of Fig. 2).
a series of measured or processed ultrasonic pulses with depth.
4.3 Thedataarefurtherprocessedandpresentedtoshowthe
3.1.8 ultrasonic pulse, n—data for one specific depth of a
FirstArrivalTime(FAT)oftheultrasonicpulseanditsRelative
short duration generated by a transmitter probe and sensed by
Energy (RE) to aid interpretation. The processed data are
the receiver probe.
plotted versus depth as a graphical representation of the
ultrasonicprofileofthetestedstructure(seeFig.2left).Special
4. Principle of the Test Method
test methods to further investigate anomalies are employed
4.1 The actual speed of sound wave propagation in concrete
where the probes are not raised together.
is dependent on the concrete material properties, geometry of
the element and wavelength of the sound waves. When
5. Significance and Use
ultrasonic frequencies (for example, >20,000 Hz) are
5.1 This method uses data from ultrasonic probes lowered
generated, Pressure (P) waves and Shear (S) waves travel
into parallel access ducts, or in a single access duct, in the deep
though the concrete. Because S waves are relatively slow, they
foundation element to assess the homogeneity and integrity of
are of no further interest in this method. In good quality
concrete between the probes. The data are used to confirm
concretetheP-wavespeedwouldtypicallyrangebetween3600
adequate concrete quality or identify zones of poor quality. If
to 4400 m/s. Poor quality concrete containing defects (for
defectsaredetected,thenfurtherinvestigationsshouldbemade
example, soil inclusion, gravel, water, drilling mud, bentonite,
byexcavationorcoringtheconcreteasappropriate,orbyother
voids, contaminated concrete, or excessive segregation of the
testing such as Test Method D1143, D4945 or D5882, and
constituent particles) has a comparatively lower P-wave speed.
measures taken to remediate the structure if a defect is
By measuring the transit time of an ultrasonic P-wave signal
confirmed.
between an ultrasonic transmitter and receiver in two parallel
5.2 Limitations:
water-filledaccessductscastintotheconcreteduringconstruc-
tion and spaced at a known distance apart, such anomalies may 5.2.1 For crosshole tests, the access ducts should preferably
be detected. Usually the transmitter and receiver are main- be made of steel to prevent debonding of the access duct from
tained at equal elevations as they are moved up or down the the concrete resulting in an anomaly.This test can assess to the
access ducts. In some cases and for special processing the integrity of the concrete mainly in the area bounded by the
probes may be deliberately offset in relative elevation and the access ducts, which means typically inside the reinforcement
cage.
use of multiple receivers either in the same access duct or in
FIG. 1 An Ultrasonic Pulse from Receiver
D6760 − 16
FIG. 2 Typical Ultrasonic Profile
5.2.2 For single hole tests the access tubes must be plastic stances if approved by the specifier but require more frequent
tubes. Testing should therefore be performed as soon as
attachment to the reinforcing cage to maintain alignment. The
practical in order to avoid debonding issues. Since the gener-
plastic material must not deform during the high temperatures
ated waves travel through the concrete around the access duct,
ofconcretecuring.Ifnotubesareinstalledduringconstruction,
unless a flaw is massive enough and very near to the access
boreholes drilled into the pile or structure can be installed after
duct it may not be detected by this method.
installation. The internal diameter of the access ducts shall be
NOTE 1—The quality of the result produced by this standard is
sufficient to allow the easy passage of the ultrasonic probes
dependent on the competence of the personnel performing it, and the
over the entire access duct length. If the access duct diameter
suitability of the equipment and facilities used. Agencies that meet the
is too large it influences the precision of arrival time and
criteria of Practice D3740 are generally considered capable of competent
and objective testing and inspection. Users of this standard are cautioned
calculated concrete wave speed.Access ducts typically have an
that compliance with Practice D3740 does not in itself assure reliable
internal diameter from 38 to 50 mm.
results. Reliable results depend on many factors; Practice D3740 provides
a means of evaluating some of those factors.
6.2 Apparatus for Determining Physical Test Parameters:
6.2.1 Weighted Measuring Tape—Aplumbbobconnectedto
6. Apparatus
a measuring tape shall be used as a dummy probe to check free
6.1 Apparatus for Allowing Internal Inspection (Access
passage through and determine the unobstructed length of each
Ducts)—To provide access for the probes, access ducts can be
access duct to the nearest 100 mm. The plumb bob shall have
preformedtubes,whicharepreferablyinstalledduringthedeep
a diameter similar to the diameter of the probes.
foundation element installation. The tubes shall preferably be
6.2.2 Magnetic Compass—A magnetic compass accurate to
mild steel for crosshole testing, and are required to be PVC or
within 10° shall be used to document the access duct designa-
equivalent for single hole testing. Plastic tubes, while not
preferred for crosshole testing, can be used in special circum- tions compared with the site layout plan. Alternately, access
D6760 − 16
ducts can be labeled based on the site plan, structure orienta- fitted inside the access ducts to minimize abrasion and gener-
tion or other methods to document access duct designations ally assist with smooth deployment of the probes.
assigned and used for reporting test results. 6.3.6 Probe Depth-Measuring Device—The signal cables
shall be passed over or through a pulley with a depth-encoding
6.3 Apparatus for Obtaining Measurements:
device to determine the depth to the location of the transmitter
6.3.1 Probes—Probes shall allow a generated or detected
and receiver on the probes in the access ducts throughout the
pulse within 125 mm of the bottom of the access duct. The
test. The design of the depth-measuring device shall be such
weight of each probe shall in all cases be sufficient to allow it
that cable slippage shall not occur. Preferably a separate
to sink under its own weight in the access ducts. The probe
depth-measuring device shall monitor each probe so the exact
housing shall be waterproof to at least 1.5 times the maximum
depth of each probe is known at all times. (Alternately a single
depth of testing.
pulley can be connected to one electronic depth encoder, but
6.3.2 Transmitter Probe—The transmitter probe shall gen-
then the probes must remain at the same known relative
erate an ultrasonic pulse with a frequency of between 30,000
elevation difference for the entire test.) The depth-measuring
Hz and 60,000 Hz.
deviceshallbeaccuratetowithin1 %oftheaccessductlength,
6.3.3 Receiver Probe—The receiver probe shall be of a
or 0.25 m, whichever is larger.
similar size and compatible design to the transmitter probe and
used to detect the arrival of the ultrasonic pulse generated by 6.4 Apparatus for Recording, Processing and Displaying
the transmitter probe. Data:
6.3.4 Probe Centralizer—If the receiver or transmitter 6.4.1 General—The signals from the transmitter and re-
probes, or both, are less than half the access duct diameter, ceiver probes and the depth-measuring device shall be trans-
each probe shall be fitted with centralizers with effective mitted to a field rugged, computerized apparatus for recording,
diameter equivalent to at least 50 % of the access duct processing and displaying the data in the form of an ultrasonic
diameter. It shall be designed to minimize any possible profile. A typical schematic arrangement for the test apparatus
snagging on irregularities in the inner access duct wall. isillustratedinFig.3.Theapparatusshallgeneratepulsesfrom
6.3.5 Signal Transmission Cables—The signal cables used the transmitter probe either at fixed depth intervals or at fixed
to deploy the probes and transmit data from the probes shall be timeintervals.Inthelattercase,thedepthshallberecordedand
sufficiently robust to support the probes’ weight. The cable assigned to each pulse captured by the apparatus for the instant
shall be abrasion resistant to allow repeated field use and of pulse generation. The rate of pulse generation by either
maintain flexibility in the range of anticipated temp
...
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: D6760 − 14 D6760 − 16
Standard Test Method for
Integrity Testing of Concrete Deep Foundations by
Ultrasonic Crosshole Testing
This standard is issued under the fixed designation D6760; 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 test method covers procedures for checking the homogeneity and integrity of concrete in deep foundation such as bored
piles, drilled shafts, concrete piles or augercast piles. This method can also be extended to diaphragm walls, barrettes, dams etc.
In this test method, all the above will be designated “deep foundation elements.” The test measures the propagation time and
relative energy of an ultrasonic pulse between parallel access ducts (crosshole) or in a single tube (single hole) installed in the deep
foundation element. This method is most applicable when performed in tubes that are installed during construction.
1.2 Similar techniques with different excitation sources exist, but these techniques are outside the scope of this test method.
1.3 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.3.1 The method used to specify how data are collected, calculated, or recorded in this standard is not directly related to the
accuracy to which data can be applied in design or other uses, or both. How one applies the results obtained using this standard
is beyond its scope.
1.4 The method used to specify how data are collected, calculated, or recorded in this test method is not directly related to the
accuracy to which data can be applied in design or other uses, or both. How one applies the results obtained using this standard
is beyond its scope.
1.5 This standard provides minimum requirements for crosshole (or single hole) testing of concrete deep foundation elements.
Plans, specifications, provisions, or combinations thereof prepared by a qualified engineer, and approved by the agency requiring
the test(s), may provide additional requirements and procedures as needed to satisfy the objectives of a particular test program.
1.6 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) shall not be considered as requirements of the standard.
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.8 Limitations—Proper installation of the access ducts is essential for effective testing and interpretation. The method does not
give the exact type of defectflaw (for example, inclusion, honeycombing, lack of cement particles, etc.) but rather only that a defect
exists. The method is limited primarily to testing the concrete between the access ducts and thus gives little information about the
concrete outside the reinforcement cage to which the access ducts are attached when the tubes are attached to the inside of the
reinforcement cage.flaw exists.
1.9 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D1143 Test Method for Piles Under Static Axial Compressive Load (Withdrawn 2005)
This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.11 on Deep Foundations.
Current edition approved June 1, 2014Dec. 1, 2016. Published July 2014January 2017. Originally approved in 2002. Last previous edition approved in 20082014 as
D6760 – 08.D6760 – 14. DOI: 10.1520/D6760-14.10.1520/D6760-16.
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.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6760 − 16
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4945 Test Method for High-Strain Dynamic Testing of Deep Foundations
D5882 Test Method for Low Strain Impact Integrity Testing of Deep Foundations
D6026 Practice for Using Significant Digits in Geotechnical Data
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 access ducts, n—preformed steel tubes, plastic tubes (for example, PVC or equivalent), or drilled boreholes, placed in the
concrete to allow probe entry in pairs to measure pulse transmission in the concrete between the probes.
3.1.2 anomaly, n—irregularity or series of irregularities observed in an ultrasonic profile indicating a possible flaw.
3.1.3 defect, n—a flaw that, because of either size or location, may significantly detract from the element’s capacity or durability.
3.1.4 depth interval, n—the maximum incremental spacing along the pile shaft between ultrasonic pulses.
3.1.5 flaw, n—any deviation from the planned shape or material (or both) of the element.
3.1.6 integrity evaluation, n—the qualitative or quantitative evaluation of the concrete continuity and consistency between the
access ducts or boreholes.
3.1.7 specifier, n—the party requesting that the tests are carried out, for example, the engineer or client.
3.1.7 ultrasonic profile, n—a combined graphical output of a series of measured or processed ultrasonic pulses with depth.
3.1.8 ultrasonic pulse, n—data for one specific depth of a short duration generated by a transmitter probe and sensed by the
receiver probe.
4. Principle of the Test Method
4.1 The actual speed of sound wave propagation in concrete is dependent on the concrete material properties, geometry of the
element and wavelength of the sound waves. When ultrasonic frequencies (for example, >20 000>20,000 Hz) are generated,
Pressure (P) waves and Shear (S) waves travel though the concrete. Because S waves are relatively slow, they are of no further
interest in this method. In good quality concrete the P-wave speed would typically range between 3600 to 4400 m/s. Poor quality
concrete containing defects (for example, soil inclusion, gravel, water, drilling mud, bentonite, voids, contaminated concrete, or
excessive segregation of the constituent particles) has a comparatively lower P-wave speed. By measuring the transit time of an
ultrasonic P-wave signal between an ultrasonic transmitter and receiver in two parallel water-filled access ducts cast into the
concrete during construction and spaced at a known distance apart, such anomalies may be detected. Usually the transmitter and
receiver are maintained at equal elevations as they are moved up or down the access ducts. In some cases and for special processing
the probes may be deliberately offset in relative elevation and the use of multiple receivers either in the same access duct or in
multiple access ducts can also be allowed. Testing of the concrete in the vicinity of the access duct can also be made with both
probes installed in a single access duct. The principles and limitations of the test and interpretation of the results are described in
the References section.
4.2 Two ultrasonic probes, one a transmitter and the other a receiver, are lowered and lifted usually in unison in to the bottom
of their respective water-filled access duct(s) to test the full shaft length from topbottom to bottom.top. The transmitter probe
generates ultrasonic pulses at frequent and regular intervals during the probes’ controlled travel rate. The probe depth and receiver
probe’s output (timed relative to the transmitter probe’s ultrasonic pulse generation) are recorded for each pulse. The receiver’s
output signals are sampled and saved as amplitudevoltage versus time (see Fig. 1) for each sampled depth. These signals can be
then nested to produce a “waterfall” diagram (see right side of Fig. 2).
4.3 The data are further processed and presented to show the first arrival First Arrival Time (FAT) of the ultrasonic pulse and
the relative energy of the signal its Relative Energy (RE) to aid interpretation. The processed data are plotted versus depth as a
graphical representation of the ultrasonic profile of the tested structure. structure (see Fig. 2 left). Special test methods to further
investigate anomalies are employed where the probes are not raised together. The References section lists further sources of
information about these special test techniques.
5. Significance and Use
5.1 This method uses data from ultrasonic probes lowered into parallel access ducts, or in a single access duct, in the deep
foundation element to assess the homogeneity and integrity of concrete between the probes. The data are used to confirm adequate
concrete quality or identify zones of poor quality. If defects are detected, then further investigations should be made by excavation
or coring the concrete as appropriate, or by other testing such as Test Method D1143, D4945 or D5882, and measures taken to
remediate the structure if a defect is confirmed.
5.2 Limitations:
D6760 − 16
FIG. 1 1 ms Duration An Ultrasonic Pulse from Receiver
FIG. 2 Typical Ultrasonic Profile
5.2.1 For crosshole tests, the access ducts should preferably be made of steel to prevent debonding of the access duct from the
concrete resulting in an anomaly. This test can assess to the integrity of the concrete mainly in the area bounded by the access ducts,
which means typically inside the reinforcement cage.
D6760 − 16
5.2.2 For single hole tests the access tubes must be plastic tubes. Testing should therefore be performed as soon as practical in
order to avoid debonding issues. Since the generated waves travel through the concrete around the access duct, unless a flaw is
massive enough and very near to the access duct it may not be detected by this method.
NOTE 1—The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the
equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing and
inspection. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on
many factors; Practice D3740 provides a means of evaluating some of those factors.
6. Apparatus
6.1 Apparatus for Allowing Internal Inspection (Access Ducts)—To provide access for the probes, access ducts can be
preformed tubes, which are preferably installed during the deep foundation element installation. The tubes shall preferably be mild
steel for crosshole testing, and are required to be PVC or equivalent for single hole testing. Plastic tubes, while not preferred for
crosshole testing, can be used in special circumstances if approved by the specifier but require more frequent attachment to the
reinforcing cage to maintain alignment. The plastic material must not deform during the high temperatures of concrete curing. If
no tubes are installed during construction, boreholes drilled into the pile or structure can be installed after installation. The internal
diameter of the access ducts shall be sufficient to allow the easy passage of the ultrasonic probes over the entire access duct length.
If the access duct diameter is too large it influences the precision of arrival time and calculated concrete wave speed. Access ducts
typically have an internal diameter from 38 to 50 mm.
6.2 Apparatus for Determining Physical Test Parameters:
6.2.1 Weighted Measuring Tape—A plumb bob connected to a measuring tape shall be used as a dummy probe to check free
passage through and determine the unobstructed length of each access duct to the nearest 100 mm. The plumb bob shall have a
diameter similar to the diameter of the probes.
6.2.2 Magnetic Compass—A magnetic compass accurate to within 10° shall be used to document the access duct designations
compared with the site layout plan. Alternately, access ducts can be labeled based on the site plan, structure orientation or other
methods to document access duct designations assigned and used for reporting test results.
6.3 Apparatus for Obtaining Measurements:
6.3.1 Probes—Probes shall allow a generated or detected pulse within 125 mm of the bottom of the access duct. The weight
of each probe shall in all cases be sufficient to allow it to sink under its own weight in the access ducts. The probe housing shall
be waterproof to at least 1.5 times the maximum depth of testing.
6.3.2 Transmitter Probe—The transmitter probe shall generate an ultrasonic pulse with a frequency of between 30 00030,000
Hz and 100 000 60,000 Hz.
6.3.3 Receiver Probe—The receiver probe shall be of a similar size and compatible design to the transmitter probe and used to
detect the arrival of the ultrasonic pulse generated by the transmitter probe.
6.3.4 Probe Centralizer—If the receiver or transmitter probes, or both, are less than half the access duct diameter, each probe
shall be fitted with centralizers with effective diameter equivalent to at least 50 % of the access duct diameter. It shall be designed
to minimize any possible snagging on irregularities in the inner access duct wall.
6.3.5 Signal Transmission Cables—The signal cables used to deploy the probes and transmit data from the probes shall be
sufficiently robust to support the probes’ weight. The cable shall be abrasion resistant to allow repeated field use and maintain
flexibility in the range of anticipated temperatures. All cable connectors or splices, if any, shall be watertight. Where the signal
transmission cables exit the access duct, suitable cable guides, pulleys or cushioning material shall be fitted inside the acce
...
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