ASTM D8295-19

Standard Test Method for Determination of Shear Wave Velocity and Initial Shear Modulus in Soil Specimens using Bender Elements

SIGNIFICANCE AND USE
5.1 The initial shear modulus (Gmax) of a soil specimen under particular stress and time conditions is an important parameter in small-strain dynamic analyses such as those to predict soil behavior or soil-structure interaction during earthquakes, explosions, and machine or traffic vibrations. Gmax can be equally important for small-strain cyclic situations such as those caused by wind or wave loading. Small-strain Gmax is also vital for non-linear analyses of large strain situations, where the larger strain soil stiffness results could come from torsional shear tests, for example. Shear wave velocity and Gmax can be used to compare different soil specimens in a laboratory testing program, and also for comparing laboratory and field measurements of these parameters.  
5.2 Torsional resonant column tests (Test Method D4015) are often used to determine properties of a soil specimen at small shear strains up to and possibly slightly beyond 0.01%. Resonant column test results can include Gmax versus time, shear modulus versus strain, damping ratio versus time and damping ratio versus strain. Bender element tests can only provide the first of these, Gmax versus time. The strain level in bender element tests is small (constant Gmax strain levels), but the strain magnitude is not known and the strain is not constant along the shear wave travel path due to material and geometric damping. Bender elements can therefore not be used to evaluate shear modulus versus strain and do not provide information about damping ratio. However, bender elements can be incorporated in a variety of different laboratory testing devices, allowing the measurement of small-strain and large-strain stiffness on the same specimen at the particular conditions of the test and possibly eliminating the need for additional resonant column tests.  
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 equipmen...
SCOPE
1.1 This test method covers the laboratory use of piezo-ceramic bender elements to determine the shear wave velocity in soil specimens. A shear wave is generated at one boundary of a soil specimen and then received at an opposite boundary. The shear wave travel time is measured, which over a known travel distance yields the shear wave velocity. From this shear wave velocity and the density of the soil specimen the initial shear modulus (Gmax) can be determined, which is the result of primary interest from bender element tests.  
1.2 This shear wave velocity determination involves very small strains and is non-destructive to a test specimen. As such, bender element shear wave velocity determinations can be made at any time and any number of times during a laboratory test.  
1.3 This test method describes the use of bender elements in a triaxial type test (for example, Test Methods D3999, D4767, D5311, or D7181), but a similar procedure may be used for other laboratory applications, like in Direct Simple Shear (Test Method D6528) or oedometer tests (for example, Test Methods D2435 and D4186). Shear wave velocity can also be determined in unconfined soil specimens held together by matrix suction.  
1.4 Shear wave velocity can be determined in different directions in a triaxial test, for example vertically and horizontally. Shear waves generated to determine shear wave velocity can also be polarized in different directions, for example a horizontally propagating shear wave with either vertical or horizontal polarization. This test method describes the use of bender elements mounted in the top platen and base pedestal of a triaxial test specimen to measure shear wave velocity in the vertical direction. With additional bender elements mounted on opposite sides of a triaxial specimen, a similar procedure may be used to determine horizontal shear wave velocity.  
1.5 A variety of different interpretation methods to evaluate ...

General Information

• Status: Published
• Publication Date: 31-Oct-2019
• ICS: 13.080.20 - Physical properties of soils
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.09 - Cyclic and Dynamic Properties of Soils

Relations

• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM D4767-11(2020) - Standard Test Method for Consolidated Undrained Triaxial Compression Test for Cohesive Soils
• Effective Date: 01-Apr-2020
• Refers: ASTM D7181-20 - Standard Test Method for Consolidated Drained Triaxial Compression Test for Soils
• Effective Date: 01-Jan-2020
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM D2216-19 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Mar-2019
• Refers: ASTM D7263-09(2018)e1 - Standard Test Methods for Laboratory Determination of Density (Unit Weight) of Soil Specimens
• Effective Date: 15-Feb-2018
• Refers: ASTM D7263-09(2018) - Standard Test Methods for Laboratory Determination of Density (Unit Weight) of Soil Specimens
• Effective Date: 15-Feb-2018
• Refers: ASTM D6528-17 - Standard Test Method for Consolidated Undrained Direct Simple Shear Testing of Fine Grain Soils
• Effective Date: 01-Aug-2017
• Refers: ASTM D4015-15 - Standard Test Methods for Modulus and Damping of Soils by Fixed-Base Resonant Column Devices
• Effective Date: 01-Oct-2015
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D3740-12a - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-May-2012
• Refers: ASTM D3740-12 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2012
• Refers: ASTM D3999-11 - Standard Test Methods for the Determination of the Modulus and Damping Properties of Soils Using the Cyclic Triaxial Apparatus
• Effective Date: 01-Nov-2011
• Refers: ASTM D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• Refers: ASTM D3740-11 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Sep-2011

Overview

ASTM D8295-19 is the internationally recognized standard test method for the determination of shear wave velocity and initial shear modulus (Gmax) in soil specimens using bender elements. Developed by ASTM International, this standard provides precise laboratory procedures for capturing key small-strain dynamic properties of soils, which are critical for geotechnical engineering applications including earthquake engineering, soil-structure interaction, and vibration analysis.

By generating a shear wave at one boundary of a soil sample and measuring the wave's travel time to the other boundary, the method enables calculation of the shear wave velocity (Vs). Combined with knowledge of the soil specimen’s density, this information is used to compute Gmax-a primary indicator of soil stiffness under very small strains.

Key Topics

• Shear Wave Velocity Measurement: The core procedure involves using piezo-ceramic bender elements to produce and detect shear waves across soil specimens. The travel time, measured between transmitter and receiver elements, is essential for determining shear wave velocity.
• Initial Shear Modulus (Gmax): Using the measured Vs and soil density, Gmax is calculated, providing insight into the soil’s stiffness under small-strain conditions relevant to a wide range of engineering analyses.
• Non-Destructive Testing: The method allows for non-destructive, repeatable measurements at any stage of a laboratory test, without affecting the integrity of the specimen.
• Versatile Applications: While the standard details application with triaxial testing setups, it can be adapted for use with direct simple shear and oedometer tests, making it suitable for various laboratory soil testing programs.
• Interpretation Methods: Time-domain interpretation (Start to Start and Peak to Peak) is specified, though other reliable methods may be used if validated.

Applications

ASTM D8295-19 has practical value across many geotechnical and civil engineering projects:

• Seismic Site Response and Earthquake Engineering: Gmax and shear wave velocity data are vital for modeling how soils will behave during earthquakes, including liquefaction and amplification studies.
• Soil-Structure Interaction: Accurate soil stiffness characterization supports safer and more cost-effective design of foundations, retaining structures, and buried utilities where dynamic loads are expected.
• Machine and Traffic Vibration Analysis: Dynamic testing helps predict and mitigate ground vibrations from construction equipment, trains, or highway traffic.
• Cyclic Loading Due to Environmental Forces: Wind, wave, or other cyclic loads acting on soils and foundations require knowledge of small-strain modulus behavior.
• Comparing Laboratory and Field Measurements: The method serves as a benchmark for correlating laboratory test results with field data, improving reliability in site investigations.

Related Standards

Many other ASTM standards complement or reference ASTM D8295-19, providing a comprehensive framework for soil characterization:

• ASTM D4015: Test Methods for Modulus and Damping of Soils by Fixed-Base Resonant Column Devices-offers alternative means for assessing modulus and damping at small strains.
• ASTM D3999, D4767, D5311, D7181: Various triaxial test methods adapted for different soil types and stress paths.
• ASTM D6528: Direct simple shear testing for fine-grained soils, compatible with bender element use.
• ASTM D2435 & D4186: Consolidation testing methods, also supporting bender element incorporation.
• ASTM D7263: Laboratory determination of soil specimen density, essential for accurate modulus calculation.
• ASTM D653: Terminology for soils and related materials, ensuring consistency in definitions.

For laboratories, researchers, and consulting engineers, following ASTM D8295-19 ensures that shear wave velocity and small-strain stiffness measurements are accurate, standardized, and comparable across projects-supporting better design, analysis, and safety in geotechnical engineering.

Keywords: ASTM D8295-19, shear wave velocity, initial shear modulus, Gmax, soil bender elements, dynamic soil properties, laboratory soil testing, triaxial testing, geotechnical engineering standards.

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: D8295 − 19
Standard Test Method for
Determination of Shear Wave Velocity and Initial Shear
Modulus in Soil Specimens using Bender Elements
This standard is issued under the fixed designation D8295; 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 proposed and used. This test method only describes two of
these, Start to Start and Peak to Peak using a single sine wave
1.1 This test method covers the laboratory use of piezo-
signal sent to the transmitter bender element. Other interpre-
ceramic bender elements to determine the shear wave velocity
tation methods producing similar results may also be used.
in soil specimens. A shear wave is generated at one boundary
of a soil specimen and then received at an opposite boundary. 1.6 Bender element measurements may not work very well
The shear wave travel time is measured, which over a known
in some situations, like in extremely stiff soils where the
travel distance yields the shear wave velocity. From this shear generated shear wave amplitude may be exceedingly small.
wave velocity and the density of the soil specimen the initial
1.7 This test method does not cover the determination of
shear modulus (G ) can be determined, which is the result of
max
compressional wave velocity in soil specimens. This measure-
primary interest from bender element tests.
ment requires a different type of piezo-ceramic element
1.2 This shear wave velocity determination involves very
configuration, and such determinations are generally not useful
smallstrainsandisnon-destructivetoatestspecimen.Assuch,
in saturated soft soil specimens as the earliest identifiable
bender element shear wave velocity determinations can be compressional wave arrival at the receiver end of a saturated
made at any time and any number of times during a laboratory
specimen will likely have been transmitted through the (rela-
test. tively incompressible) specimen pore water rather than the
(compressible) soil skeleton.
1.3 This test method describes the use of bender elements in
a triaxial type test (for example, Test Methods D3999, D4767,
1.8 Units—The values stated in SI units are to be regarded
D5311,or D7181), but a similar procedure may be used for
as standard. No other units of measurement are included in this
other laboratory applications, like in Direct Simple Shear (Test
standard.
Method D6528) or oedometer tests (for example,Test Methods
1.9 All observed and calculated values shall conform to the
D2435 and D4186). Shear wave velocity can also be deter-
guidelines for significant digits and rounding established in
mined in unconfined soil specimens held together by matrix
Practice D6026, unless superseded by this test method.
suction.
1.9.1 Theproceduresusedtospecifyhowdataarecollected/
1.4 Shear wave velocity can be determined in different
recorded and calculated in the standard are regarded as the
directions in a triaxial test, for example vertically and horizon-
industry standard. In addition, they are representative of the
tally. Shear waves generated to determine shear wave velocity
significant digits that generally should be retained. The proce-
can also be polarized in different directions, for example a
dures used do not consider material variation, purpose for
horizontally propagating shear wave with either vertical or
obtaining the data, special purpose studies, or any consider-
horizontal polarization. This test method describes the use of
ations for the user’s objectives; and it is common practice to
bender elements mounted in the top platen and base pedestal of
increase or reduce significant digits of reported data to be
a triaxial test specimen to measure shear wave velocity in the
commensuratewiththeseconsiderations.Itisbeyondthescope
vertical direction.With additional bender elements mounted on
of these test methods to consider significant digits used in
opposite sides of a triaxial specimen, a similar procedure may
analysis methods for engineering data.
be used to determine horizontal shear wave velocity.
1.10 This standard does not purport to address all of the
1.5 Avariety of different interpretation methods to evaluate
safety concerns, if any, associated with its use. It is the
the shear wave travel time in a soil specimen have been
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
mine the applicability of regulatory limitations prior to use.
Rock and is the direct responsibility of Subcommittee D18.09 on Cyclic and
1.11 This international standard was developed in accor-
Dynamic Properties of Soils.
dance with internationally recognized principles on standard-
Current edition approved Nov. 1, 2019. Published December 2019. DOI:
10.1520/D8295-19 ization established in the Decision on Principles for the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8295 − 19
Development of International Standards, Guides and Recom- 3.2.2 receiver bender element, n—aseries-connectedbender
mendations issued by the World Trade Organization Technical element used to detect the arrival of a shear wave propagating
Barriers to Trade (TBT) Committee. through the soil specimen.
3.2.3 transmitter bender element, n—a parallel-connected
2. Referenced Documents
bender element used to generate a shear wave through the soil
2.1 ASTM Standards: specimen.
D653 Terminology Relating to Soil, Rock, and Contained 3.2.3.1 Discussion—The receiver bender element can be
Fluids used as a shear wave transmitter and the transmitter bender
D2216 Test Methods for Laboratory Determination of Water element as a shear wave receiver, but they will function less
(Moisture) Content of Soil and Rock by Mass efficiently (i.e., the receiver signal amplitude will be smaller).
D2435 Test Methods for One-Dimensional Consolidation
Properties of Soils Using Incremental Loading 4. Summary of Test Method
D3740 Practice for Minimum Requirements for Agencies
4.1 The test specimen and triaxial equipment are prepared
Engaged in Testing and/or Inspection of Soil and Rock as
and assembled as for a triaxial test. The specified back
Used in Engineering Design and Construction
pressure, confining pressure and deviator stress are then
D3999 Test Methods for the Determination of the Modulus
applied to the triaxial test specimen.
and Damping Properties of Soils Using the CyclicTriaxial
4.2 For any bender element measurement, a shear wave is
Apparatus
generated by the transmitter bender element at one specimen
D4015 Test Methods for Modulus and Damping of Soils by
boundary, that propagates through the soil specimen and is
Fixed-Base Resonant Column Devices
picked up by the receiver bender element at the opposite
D4186 Test Method for One-Dimensional Consolidation
specimen boundary. The known shear wave travel length
Properties of Saturated Cohesive Soils Using Controlled-
(bender element tip-to-tip distance) divided by the shear wave
Strain Loading
travel time (measured on the recorded transmitter and receiver
D4767 Test Method for Consolidated Undrained Triaxial
benderelementtraces)istheresultingshearwavevelocity.The
Compression Test for Cohesive Soils
small-strain initial shear modulus, G , of the soil specimen is
max
D5311 Test Method for Load Controlled Cyclic Triaxial
determined from the measured shear wave velocity and speci-
Strength of Soil
men bulk density.
D6026 Practice for Using Significant Digits in Geotechnical
Data
5. Significance and Use
D6528 Test Method for Consolidated Undrained Direct
Simple Shear Testing of Fine Grain Soils
5.1 The initial shear modulus (G ) of a soil specimen
max
D7181 Test Method for Consolidated DrainedTriaxial Com-
under particular stress and time conditions is an important
pression Test for Soils
parameter in small-strain dynamic analyses such as those to
D7263 Test Methods for Laboratory Determination of Den-
predict soil behavior or soil-structure interaction during
sity (Unit Weight) of Soil Specimens
earthquakes, explosions, and machine or traffic vibrations.
G can be equally important for small-strain cyclic situations
max
3. Terminology
such as those caused by wind or wave loading. Small-strain
G is also vital for non-linear analyses of large strain
3.1 Definitions:
max
situations, where the larger strain soil stiffness results could
3.1.1 For definitions of common technical terms used in this
come from torsional shear tests, for example. Shear wave
standard, refer to Terminology D653.
velocity and G can be used to compare different soil
3.1.2 initial shear modulus, G or G,n—the shear max
max o
specimens in a laboratory testing program, and also for
modulus for soils determined at very small strain amplitude
–3
comparing laboratory and field measurements of these param-
(for example, a shear strain of 10 % and below) at a
eters.
particular stress condition and time, where the shear modulus
seems to be constant plotted against the logarithm of strain.
5.2 Torsional resonant column tests (Test Method D4015)
are often used to determine properties of a soil specimen at
3.1.3 travel time, n—in propagating waves, the time interval
small shear strains up to and possibly slightly beyond 0.01%.
it takes for a shear wave to propagate through soil from a
Resonant column test results can include G versus time,
source to a receiver.
max
shear modulus versus strain, damping ratio versus time and
3.2 Definitions of Terms Specific to This Standard:
damping ratio versus strain. Bender element tests can only
3.2.1 bender element, n—an electro-mechanical transducer
provide the first of these, G versus time. The strain level in
max
consisting of two thin piezo-ceramic plates with conducting
bender element tests is small (constant G strain levels), but
max
surfaces sandwiched between them and on the outside.
the strain magnitude is not known and the strain is not constant
along the shear wave travel path due to material and geometric
damping. Bender elements can therefore not be used to
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
evaluate shear modulus versus strain and do not provide
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
information about damping ratio. However, bender elements
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. can be incorporated in a variety of different laboratory testing
D8295 − 19
devices, allowing the measurement of small-strain and large-
strain stiffness on the same specimen at the particular condi-
tionsofthetestandpossiblyeliminatingtheneedforadditional
resonant column tests.
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/sampling/inspection/etc. 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 Triaxial Testing Equipment—The triaxial equipment and
ancillary equipment is the same as in the triaxial standard
method being followed.
6.2 Transmitter Bender Element—A parallel-connected
bender element having a wire connected to both outer surface
electrodes and another wire is connected to the center elec-
trode.Thepolarizationsofthetwoceramicplatesinthisbender
element (sandwiched between the three electrode surfaces) are
in the same direction, towards one side.The transmitter bender
element is permanently mounted in the end platen opposite of
the receiver bender element. The wires and connections to the
transmitter bender element should be shielded to reduce any
ambient electrical noise that could be included in the driving
signal sent to the transmitter element.
6.3 Receiver Bender Element—A series-connected bender
element having a wire connected to one outer surface electrode
and another wire connected to the opposite outer surface
electrode. The polarizations of the two ceramic plates in this
bender element (sandwiched between the three electrode sur-
faces) are in opposite directions, towards the center electrode.
FIG. 1 Receiver Bender Element Mounted in a Triaxial Cell Pedes-
The wires and connections to the receiver bender element
tal
should be shielded to reduce any ambient electrical noise that
could be picked up in the recorded receiver signal.
6.3.1 Fig. 1 shows an example of a receiver bender element
function in the recording equipment. The time delay should be
permanently mounted in a triaxial cell pedestal.Approximately
long enough for all the movements in the receiver bender
onethirdofitslengthisrigidlygluedintoaslotinthepedestal,
elementfromthepreviousshearwavepulsetohavecompletely
one third passes through a clear slot filled with soft silicone in
died out. For typical triaxial testing, a conservative time delay
the filter stone, and one third protrudes into the soil specimen.
could be about 0.1 second.
Other bender element configurations may be used.
6.5 Data Recorder—Either a stand-alone digital storage
6.3.2 It can be advantageous to have the receiver bender
oscilloscope or an oscilloscope interface connected to a com-
element mounted in the end platen with least mechanical
puter. It must have two input channels, one for each of the
vibrations (most stationary). With an actuator situated in the
bender element cables. Single-ended (common ground) de-
top of a load frame connected to the triaxial piston and top
vices are often used, but there can be instances where differ-
platen, the receiver bender element would preferably be
ential inputs are advantageous. For typical measurements on
mounted in the base platen (pedestal) of the triaxial cell.
triaxial specimens, the unit must have a time resolution of at
–6
6.4 Function Generator—A device used to generate a driv- least one microsecond (1 µs = 10 s) and an amplitude
–5
ing signal to the transmitter bender element. It must be able to resolution of at least ten microvolt (10 V) for the receiver
generate a single-period sine wave pulse with an adjustable signal. The unit must be able to display the superimposed time
frequency typically within the range from 1 kHz to 50 kHz. traces from both bender elements as a measurement is taken,
The amplitude of the generated sine wave should be sufficient and preferably have movable cursors in order to interpret the
that a clearly recognizable received signal is apparent. It is measured shear wave travel time. The unit should have a
advantageous if this function generator can be programmed to delayed trigger function, such that the very start of the
automatically send single-period sine wave pulses with a transmitter signal is recorded. The unit should preferably have
specified time delay between them in order to use an averaging an averaging function, where the measurements from several
D8295 − 19
consecutive shear wave pulses can be averaged in order to can be made on the triaxial top platen and base pedestal to
remove random noise components from the receiver signal. assist in orienting them correctly during equipment assembly.
7.4.1 Bender element measurements in the form of plots
6.6 Additional Power Amplifiers and Signal Filters—Such
(timetracesseenonthescreenofthedatarecordingdevice)are
units should be avoided in the connections between the bender
usually presented with the same polarity. For example, if the
elements and the data recorder, as they can distort the signals
transmitter trace first starts in the upwards direction (positive
and introduce errors in the shear wave travel time measure-
voltage), the first significant movement of the receiver trace is
ments.Ifapoweramplifierisabsolutelynecessarybetweenthe
also upward. The alignment marks in 7.3 are made such that
function generator and the transmitter bender element, it
the top platen orientation relative to the base pedestal will
should be placed prior to the connection to the data recorder. If
produce the same polarity in the resulting bender element
the receiver signal contains excessive random electrical noise
traces. Otherwise, if one of the bender elements happens to be
making interpretation difficult, it is preferable to eliminate this
oriented 180° from this, the recording equipment may have a
noise by using the averaging function of the data recorder
function by which one of the traces can be inverted to get
instead of using a separate signal filter that could adversely
similar polarity in the two traces.
affect the measurements.
7.5 Fig. 2 shows an example of how the bender elements
7. Preparation of Apparatus
and electronics are connected for taking shear wave velocity
determinations. The function generator sends a driving signal
7.1 The preparation of the triaxial equipment is the same as
(also called the transmitter signal) to the transmitter bender
in the standard method being followed.
element and one channel of the data recorder. This driving
7.2 A function check of both the transmitter and receiver
signal causes the transmitter bender element to move, which
benderelementsshouldbeperformedbeforeeachuse.Thiscan
generates a shear wave. The cable from the receiver bender
be done by sending a square wave signal to either bender
element is connected to a second input channel of the data
element while holding this close to one’s ear. If functioning
recorder. The receiver signal is generated by the receiver
properly,aslightclickingsoundshouldbeheard.Alternatively,
bender element and is proportional to the movement it expe-
both bender elements can be tapped lightly on the sides, for
riences upon arrival of the shear wave.
example with a finger or pencil. If functioning properly, the
signals on the recording device should show responses each
8. Calibration
time the bender elements are tapped.
8.1 The bender elements themselves may have a time delay,
7.3 The shear wave travel distance is the tip-to-tip distance
T , that should be corrected for in the measured shear wave
c
between the transmitter and receiver bender elements within
travel time. Such a time delay is usually very small, but can be
the soil specimen. Because the lengths of each bender element
important when measuring shear wave travel time
...