ASTM D5778-20

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: D5778 − 20
Standard Test Method for
Electronic Friction Cone and Piezocone Penetration Testing
of Soils
This standard is issued under the fixed designation D5778; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 1.7 All observed and calculated values shall conform to the
guidelines for significant digits and rounding established in
1.1 This test method covers the procedure for determining
Practice D6026, unless superseded by this test method.
theresistanceofafrictionconeorapiezoconeasitisadvanced
1.7.1 Theproceduresusedtospecifyhowdataarecollected/
into subsurface soils at a steady rate.
recorded and calculated in the standard are regarded as the
1.2 This test method applies to electronic friction cones and
industry standard. In addition, they are representative of the
does not include hydraulic, pneumatic, or free-fall cones,
significant digits that generally should be retained. The proce-
although many of the procedural requirements herein could
dures used do not consider material variation, purpose for
apply to those cones. Also, offshore/marine Cone Penetration
obtaining the data, special purpose studies, or any consider-
Testing (CPT) systems may have procedural differences be-
ations for the user’s objectives; and it is common practice to
cause of the difficulties of testing in those environments (for
increase or reduce significant digits of reported data to be
example, tidal variations, salt water and waves). Field tests
commensuratewiththeseconsiderations.Itisbeyondthescope
using mechanical-type cones are covered elsewhere by Test
of these test methods to consider significant digits used in
Method D3441.
analysis methods for engineering data.
1.3 This test method can be used to determine pore water 1.8 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
pressures developed during the penetration when using a
properly saturated piezocone. Pore water pressure dissipation, responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
after a push, can also be monitored for correlation to time rate
of consolidation and permeability. mine the applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accor-
1.4 Additional sensors, such as inclinometer, seismic (Test
dance with internationally recognized principles on standard-
Methods D7400), resistivity, electrical conductivity, dielectric,
ization established in the Decision on Principles for the
and temperature sensors, may be included in the cone to
Development of International Standards, Guides and Recom-
provide additional information. The use of an inclinometer is
mendations issued by the World Trade Organization Technical
recommended since it will provide information on potentially
Barriers to Trade (TBT) Committee.
damaging situations during the sounding process.
1.5 CPT data can be used to interpret subsurface 2. Referenced Documents
stratigraphy, and through use of site specific correlations, they 2
2.1 ASTM Standards:
canprovidedataonengineeringpropertiesofsoilsintendedfor
D653Terminology Relating to Soil, Rock, and Contained
use in design and construction of earthworks and foundations
Fluids
for structures.
D3441Test Method for Mechanical Cone Penetration Test-
ing of Soils
1.6 Units—The values stated in SI units are to be regarded
D3740Practice for Minimum Requirements for Agencies
asstandard.Nootherunitsofmeasurementareincludedinthis
Engaged in Testing and/or Inspection of Soil and Rock as
standard. Reporting of test results in units other than SI shall
Used in Engineering Design and Construction
not be regarded as nonconformance with this test method
D6026Practice for Using Significant Digits in Geotechnical
Data
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.02 on Sampling and
Related Field Testing for Soil Evaluations. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
CurrenteditionapprovedJune1,2020.PublishedJuly2020.Originallyapproved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 1995. Last previous edition approved in 2012 as D5778–12. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D5778-20. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5778 − 20
D7400Test Methods for Downhole Seismic Testing 3.2.13 friction reducer, n—local and symmetrical enlarge-
ment of the diameter of a push rod to obtain a reduction of the
friction along the push rods.
3. Terminology
3.2.14 friction sleeve, n—anisolatedcylindricalsectionofa
3.1 Definitions:
cone upon which the friction component of penetration resis-
3.1.1 Fordefinitionsofcommontechnicaltermsusedinthis
tance develops.
standard, see Terminology D653.
3.2.15 friction sleeve resistance, f,n—the friction compo-
s
3.2 Definitions of Terms Specific to This Standard:
nent of cone resistance developed on a friction sleeve, equal to
3.2.1 apparent load transfer, n—resistance measured on
the shear force applied to the friction sleeve divided by the
either the tip or friction sleeve of a friction cone while that
friction sleeve surface area. Also referred to as local side
element is in a no-load condition but the other element is
friction or sleeve friction.
loaded.
3.2.16 full-scale output, n—the output of an electronic
3.2.2 baseline, n—a set of zero load readings that are used
transducer when loaded to 100% rated capacity.
as reference values during performance of testing and calibra-
3.2.17 measuring system, n—all sensors and auxiliary parts
tion.
used to transfer and/or store the electrical signals generated
3.2.3 cone tip, n—the conical point of a cone on which the
during the cone penetration test.
end bearing resistance is developed.
3.2.17.1 Discussion—The measuring system normally in-
cludes components for measuring force (cone resistance,
3.2.4 cone penetration test, n—pushing of a cone at the end
sleeve friction), pressure (pore pressure), inclination, clock
ofaseriesofcylindricalpushrodsintothegroundataconstant
time and penetration length.
rate of penetration. Also referred to as a cone sounding.
3.2.18 penetration depth, n—vertical depth of the base of
3.2.5 cone, n—assembly containing the cone tip, friction
the cone, relative to a fixed point.
sleeve, any other sensors and measuring systems as well as the
3.2.19 penetration length, n—sumofthelengthsofthepush
connection to the push rods.
rods and the cone.
3.2.6 cone tip resistance, q ,n—the measured end-bearing
c
3.2.20 piezocone porewater pressure measurement location:
component of cone resistance, equal to the vertical force
u ,u ,u ,n—fluid pressure measured by the piezocone at
1 2 3
applied to the cone tip divided by the cone base area.
specific locations (2, 3, 4) : u —porous filter location on the
3.2.7 corrected total cone tip resistance, q,n—cone tip
t
midface or tip of the cone, u —porous filter location at the
resistance corrected for water pressure acting behind the cone
shoulder position in the cylindrical extension of the cone tip
tip (see 13.1.1).
(standard location) and, u —porous filter location behind the
3.2.7.1 Discussion—Correction for water pressure requires
friction sleeve.
measuring water pressures with a piezocone element posi-
3.2.21 pore water pressure, n—pore water pressure mea-
tioned behind the cone tip at location u (See section 3.2.20).
sured during penetration.
3.2.8 electronic cone, n—a cone that uses transducers to
3.2.22 pore water pressure ratio, B ,n—the ratio of excess
q
obtain the measurements.
pore water pressure, ∆u , measured with a piezocone element
positioned behind the cone tip at location u (see 3.2.20)to
3.2.9 electronic piezocone, n—an electronic cone that can
corrected total cone tip resistance q, minus the total vertical
measure the pore water pressure simultaneously with the cone
t
overburden stress, σ .
tip resistance and the friction sleeve resistance.
vo
3.2.23 push rods, n—the tubes or rods used to advance the
3.2.10 equilibrium pore water pressure, u ,n—at rest water
cone.
pressure at depth of interest. Also referred to as piezometric
pressure.
3.3 Abbreviations:
3.3.1 CPT—cone penetration test.
3.2.11 excess pore water pressure, ∆u, n—pore water pres-
3.3.2 FSO—full scale output.
sureinexcessoftheequilibriumporewaterpressurecausedby
the penetration of the cone into the ground.
3.3.3 MO—measured output.
3.2.11.1 Discussion—Excess pore water pressure can either
be positive or negative for filters with a piezocone element 4. Summary of Test Method
positioned behind the cone tip at location u (see 3.2.20).
4.1 Acone is advanced through the soil at a constant rate of
3.2.12 friction ratio, R,n—the ratio of the friction sleeve 20 mm/s. The force on the cone tip required to penetrate the
f
resistance, f , to the cone tip resistance, q , with the latter soil is measured using an electric transducer. The cone tip
s c
measured at the depth for the middle of the friction sleeve, resistance q iscalculatedbydividingtheverticalforceapplied
c
expressed as a percentage. to the cone tip by the cone base area.
NOTE 1—Some methods to interpret CPTdata use friction ratio defined
as the ratio of sleeve friction, f , to cone tip resistance corrected for pore
s
pressure effects q, (1). It is not within the scope of this standard to The boldface numbers given in parentheses refer to a list of references at the
t
recommend which methods of interpretation are to be used. end of the text.
D5778 − 20
evaluation of site stratigraphy, engineering properties, homo-
geneity and depth to firm layers, voids or cavities, and other
discontinuities. The use of a friction sleeve and pore water
pressure element can provide an estimate of soil classification,
and correlations with engineering properties of soils. When
properly performed at suitable sites, the test provides a rapid
means for determining subsurface conditions.
5.2 This test method provides data used for estimating
engineering properties of soil intended to help with the design
and construction of earthworks, the foundations for structures,
and the behavior of soils under static and dynamic loads.
5.3 Thismethodteststhesoilinsituandsoilsamplesarenot
obtained during the test. The interpretation of the results from
this test method provides estimates of the types of soil
penetrated. Engineers may obtain soil samples from parallel
borings for correlation purposes but prior information or
experience may preclude the need for borings.
NOTE 2—The quality of the results produced by this standard is
dependent on the competence of the personal performing the test, 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 and Practice
D3740 provides a means of evaluating some of those factors.
6. Interferences
6.1 Refusal, deflection, or damage to the cone may occur in
coarse grained soil deposits with maximum particle sizes that
approach or exceed the diameter of the cone.
6.2 Partially lithified and lithified deposits may cause
refusal, deflection, or damage to the cone.
FIG. 1 Piezocone Pore Water Pressure Measurement Locations
6.3 Push rods can be damaged or broken under extreme
(courtesy ConeTec Data Services)
loadings.Theamountofforcethatpushrodsareabletosustain
isafunctionoftheunrestrainedlengthoftherodsandtheweak
4.2 A friction sleeve is present on the cone immediately
links in the string, such as push rod joints and push rod-cone
behindtheconetip,andtheforceexertedonthefrictionsleeve
connections. The force at which rods may break is a function
is measured using an electric transducer. The friction sleeve
of the equipment configuration and ground conditions during
resistance, f iscalculatedbydividingtheshearforceappliedto
s
penetration. Excessive rod deflection is the most common
the friction sleeve by the surface area of the friction sleeve.
cause for rod breakage.
4.3 Most modern cones are capable of registering pore
7. Apparatus
water pressure induced during advancement of the cone using
anelectricpressuretransducer.Theseconesareformallycalled
7.1 Cone—The cone shall meet requirements as given
“electronic piezocones,” but given their prevalence they are
below and in 10.1. In a conventional cone, the forces at the
often simply referred to as “cones.” The dissipation of either
cone tip and friction sleeve are measured by two load cells
positive or negative excess pore water pressure can be moni-
within the cone. (Fig. 2)
tored by stopping penetration, unloading the push rods, and
7.1.1 In the subtraction-type cone (Fig. 2a) the cell nearest
recordingporewaterpressureasafunctionoftime.Whenpore
the cone tip measures the compressive force on the cone tip,
water pressure becomes constant it is measuring the equilib-
while the second cell measures the sum of the compressive
rium value (designated u ) at that depth.
forces on both the cone tip and friction sleeve. The compres-
4.4 The forces and, if applicable, pressure readings are sive force from the friction sleeve portion is then computed by
taken at penetration length intervals of no more than 50 mm. subtraction. This cone design is common in the industry
Improved resolution may often be obtained at 20- or 10-mm because of its rugged design, even though the calculated
interval readings. friction sleeve force may not be as accurate since it is very
small compared to the cone tip force.
5. Significance and Use
7.1.2 In the compression-type cone (Fig. 2b) there are
5.1 Tests performed using this test method provide a de- separate load cells for the cone tip and the friction sleeve.This
tailed record of cone tip resistance, which is useful for design results in a higher degree of accuracy in friction sleeve
D5778 − 20
FIG. 2 Configurations for Electric Friction-Cone Penetrometers (1) Showing: (a) Subtraction type, (b) Compression type, and (c) Ten-
sion type (courtesy ConeTec Data Services)
measurement, but may be more susceptible to damage under Cone tips that have worn to the operating tolerance shown in
extreme loading conditions. Fig. 3 shall be replaced.
7.1.3 Designsarealsoavailablewhereboththeconetipand
7.3 Friction Sleeve—The outside diameter of the manufac-
sleeve load cells are separate, but where the load cell for the
turedfrictionsleeveandtheoperatingdiameterareequaltothe
friction sleeve operates in tension (Fig. 2c).
diameter of the base of the cone with a tolerance of+0.35 mm
7.1.4 Typicalgeneralpurposeelectronicconesaremanufac-
and−0.0 mm, but not more than 36.1 mm for a 10-cm cone
tured to full scale outputs (FSO) equivalent to net loads of 100
and 44.2 mm for a 15-cm cone. The friction sleeve is made
to 200 kN. Often, weak soils are the most critical in an
from high strength steel of a type and hardness to resist wear
investigation program, and to gain better resolution, the FSO
due to abrasion by soil. Chrome-plated steel is not recom-
can be lowered. However, this may place electrical compo-
mendedduetodifferingfrictionalbehavior.Thesurfaceareaof
nents at risk if overloaded in stronger soils, in which case
2 2
thefrictionsleeveis150cm 62%fora10-cm coneand225
pre-boring may be required to avoid damage. The selection of
2 2
cm 62% for a 15-cm cone. If it has been demonstrated that
cone type and resolution should consider such factors as
comparableresultsareobtained,thesurfaceareaofthefriction
practicality, availability, calibration requirements, cost, risk of
sleeve for a 15-cm cone can be adjusted to a minimum of 200
damage, and preboring requirements.
cm 62%.
7.2 Cone Tip—Nominal dimensions, with manufacturing
and operating tolerances, for the cone are shown on Fig. 3.
NOTE4—Iftheconebaseareaisalteredtoothervalues,asprovidedfor
in Note 2, the surface area of the friction sleeve should be adjusted
NOTE 3—In some applications it may be desirable to scale the cone
proportionally to the cone base area ratio.
diameter down to a smaller projected area. Cones with 5 cm projected
area find use in the field applications and even smaller sizes (1 cm ) are
7.3.1 The top diameter of the sleeve must not be smaller
used in the laboratory for research purposes. These cones should be
than the bottom diameter or significantly lower sleeve resis-
designedwithdimensionsadjustedproportionallytothesquarerootofthe
tance will occur. The top and bottom of the sleeve should be
diameter ratio. In thinly layered soils, the diameter affects how accurately
thelayersmaybesensed.Smallerdiameterconesmaysensethinnerlayers periodically checked for wear with a suitable tool. Normally,
more accurately than larger cones.
the top of the sleeve will wear faster than the bottom. Friction
sleeves that have worn to the operating tolerance shall be
7.2.1 The cone tip is made of high strength steel of a type
and hardness suitable to resist wear due to abrasion by soil. replaced.
D5778 − 20
FIG. 3 Manufacturing and Operating Tolerances of Cone Tips (5) (courtesy ConeTec Data Services)
NOTE5—Theeffectscausedbyconediameterchangesontipandsleeve
7.3.2 Friction sleeves must be designed with equal end
resistance are dependent on the magnitude of diameter increase, location,
areas,whichareexposedtowaterpressures (1, 5, 6, 7, 8).This
and soil conditions. If there is question regarding a specific design with
will remove the tendency for unbalanced end forces to act on
diameter increases, comparison studies can be made to a cone with
the sleeve. Sleeve design must be checked in accordance with
constant diameter. Most practitioners feel that diameter increases equiva-
A1.6 to ensure proper response. lent to addition of a friction reducer with area increases of 15 to 20%
should be restricted to a location at least eight to ten cone diameters
7.4 Gap—The gap (annular space) between the cylindrical
behind the friction sleeve.
extension of the cone tip base and the other elements of the
7.6 Cone Axis—The axis of the cone tip, the friction sleeve,
cone shall be kept to the minimum necessary for operation of
and the remainder of the cone must be coincident.
the sensing devices and shall be designed and constructed in
such a way to prevent the entry of soil particles. These gap 7.7 Force Sensing Devices—The typical force sensing de-
vice is a strain gauge load cell that contains temperature
requirements also apply to the gaps at either end of the friction
sleeve and to other elements of the cone. compensated bonded strain gauges. The configuration and
locationofstraingaugesshouldbesuchthatmeasurementsare
7.4.1 The gap between the cylindrical extension of the cone
tip and other elements of the cone must not be larger than 5 not influenced by possible eccentricity of loading.
7.7.1 The transducers shall have an accuracy of at least
mm.
7.4.2 If a seal is placed in the gap, it should be properly 6100 kPa or 5% of the reading (whichever is larger), except
if the transducer is dedicated to measuring the friction sleeve
designed and manufactured to prevent entry of soil particles. It
must have a deformability at least two orders of magnitude resistance, in which case the precision shall be at least 15 kPa
greater than the material comprising the load transferring or 15 % of the reading (whichever is larger).
components of the sensing devices in order to prevent load
7.8 Electronic Piezocone—A piezocone can contain porous
transfer from the cone tip to the sleeve.
filter element(s), pressure transducer(s), and fluid filled ports
7.5 Diameter Requirements—The cone shall have the same connecting the elements to the transducer to measure pore
diameter as the cone tip (that is, equal to the diameter of the water pressure. Fig. 4 shows some common design types used
2 2
base of the cone withatoleranceof+35mmand–0.0mm,but in practice for 10-cm and 15-cm piezocones (with ideal
not more than 36.1 mm for a 10-cm cone and 44.2 mm for a dimensions).
15-cm cone) for the complete length of the cone (5, 9, 10). 7.8.1 The pore water pressure measurement location of the
7.5.1 Forsomeconedesigns,itmaybedesirabletoincrease porous element shall be either in the cone tip (Type 1 or u ),
the diameter of the cone body to house additional sensors or immediately behind the cone tip (Type 2 or u ) or immediately
reduce friction along push rods. These diameter changes are behind the friction sleeve (Type 3 or u ). Some piezocones
acceptable if they do not have significant influence on tip and used for research purposes may have multiple measurement
sleeve data, and therefore these diameter changes shall be at locations. The Type 2 piezocone is preferred to allow correc-
least 400 mm from the cylindrical extension of the cone tip tion of tip resistances. Moreover, this type is less subject to
2 2
base for a 10-cm cone and 500 mm for a 15-cm cone. If the damage and abrasion, and shows fewer compressibility effects
cone diameter is not constant, information on diameters of the (1, 8). However, Type 2 cones may be subject to cavitation at
complete cone shall be reported. shallow depths in dense soils because the zone behind the
D5778 − 20
FIG. 4 Cone Design Configurations: (a) Electronic Friction-type, (b) Type 1 Piezocone, (c) Standard 10-cm Type 2 Piezocone, and (d)
15-cm Type 2 Version (7) (courtesy ConeTec Data Services)
height of cylindrical extension is a zone of dilation in drained or gravel), the pore water pressure will equalize the equilib-
soils. Similar response can occur in stiff fissured clays and rium pore pressure within seconds or minutes. In low perme-
crusts (1).Porewaterpressuremeasurementsobtainedatthe u ability materials such as high plasticity clays, equalization can
location are more effective for dissipation readings, compress- takemanyhours.Ifthegoaloftheexplorationprogramisonly
ibility determinations and layer detection, particularly in fis- to acquire equilibrium pore water pressures in sands, some of
sured soils and materials prone to cause cavitation of Type 2 the preparation procedures for pore water pressure measuring
piezocones, but are more subject to wear and damage (4, 11). can be relaxed, such as deairing fluids. However, such relax-
7.8.2 Numerous design and configuration aspects can affect ation shall be reported in detail, including on each pore
themeasurementofporewaterpressures.Variablessuchasthe pressure graph generated with such relaxed preparation proce-
element location, design and volume of ports, and the type and dures.
degreeofsaturationofthefluids,cavitationoftheelementfluid 7.8.4 The pressure transducer is normally housed near the
system and resaturation lag time, depth and saturation of soil cone tip. For dynamic pressure measurements, the filter and
during testing all affect the pore water pressure measured portsarefilledwithdeairedfluidandthevolumeofconnecting
during testing and dissipation tests of pore water pressures (2, ports to the transducer should be minimized. The transducer
3, 4, 8). It is beyond the scope of the procedure to address all shall have an accuracy of at least 25 kPa or 3% of the reading
of these variables. As a minimum, complete information shall (whichever is larger).
be reported as to the design, configuration, and the preparation 7.8.5 Element—The element is a fine porous filter made
of the piezocone system that is used for the particular sound- fromplastic,sinteredsteelorbronze,orceramic.Theporesize
ing. should be less than 100 micron. Different materials have
7.8.3 Measurement of equilibrium pore water pressures different advantages. Smearing of metallic element openings
during pauses in testing are more straightforward. The pres- by hard soil grains may reduce dynamic response of the
ence of air entrained in the system only affects dynamic system, thus these elements are normally not used for Type 1
response. In high permeability soils (for example, clean sands cones, but best suited for Type 2 or Type 3 cones. Ceramic
D5778 − 20
elements are very brittle and may crack when loaded, but (see 12.1.2) while the magnitude of thrust can fluctuate. The
perform well for Type 1 cones as they reduce compressibility thrust machine must be anchored or ballasted, or both, so that
concerns. Polypropylene plastic elements are most commonly it provides the necessary reaction for the cone and does not
used in practice, particularly for Type 2 and Type 3 cones, but move relative to the soil surface during thrust.
they may be inappropriate for environmental type CPTs where
NOTE6—Conepenetrationsoundingsusuallyrequirethrustcapabilities
contaminant detection is sought.
rangingfrom100to200kNforfullcapacity.Highmassballastedvehicles
7.8.6 Fluids for Saturation—Pureglycerineorsiliconeoilis
can cause soil surface deformations, which may affect cone resistance(s)
measured in near surface layers.Anchored or ballasted vehicles, or both,
most often applied for deairing elements that are used to
may induce changes in ground surface reference level. If these conditions
measure the dynamic response. These stiff viscous oils have
are evident, they should be noted in reports.
lesstendencytocavitate,althoughcavitationmaybecontrolled
7.13 Other Sensing Devices—Other sensing devices can be
by the effective pore size of the element mounting surfaces.
included in the cone to provide additional information during
Water or water mixtures can be used for the fluid if the entire
the sounding.These instruments are normally read at the same
sounding will be submerged, or if the dynamic response is not
continuous rate as tip, sleeve, and pore water pressure sensors,
important.Thefluidsaredeairedusingproceduresdescribedin
or alternatively, during pauses in the push (often at 1-m rod
11.1.
breaks). Typical sensors are inclinometer, temperature, resis-
7.9 Data Acquisition System—The signals from the cone
tivity (or its reciprocal, electrical conductivity), or seismic
transducers are to be displayed at the surface during testing as
sensors. The use of an inclinometer is highly recommended
a continuously updated plot against penetration length. The
since it will provide information on potentially damaging
data are also to be recorded electronically on the same data
situations during the sounding process. An inclinometer can
acquisition system for subsequent processing.
provide a useful depth reliability check because it provides
7.9.1 Theelectronicdatafilesshallincludeproject,location,
information on verticality. In addition, it will allow for correc-
operator, and data format information (for example, channel,
tion of the penetration length to the penetration depth during
units, corrected or uncorrected, etc.) so that the data can be
post-processing of the data.
understood when reading the file with a text editor.
7.10 Push Rods—Steel rods are required having a cross
8. Reagents and Materials
sectional area adequate to sustain, without buckling, the thrust
8.1 O-Ring Compound—A petroleum or silicon compound
required to advance the cone. For systems that use cables, the
for facilitating seals with O-rings. Use of silicon compounds
cable is prestrung through the rods prior to testing. Push rods
may impede repair of strain gages if the strain gauge surface is
are typically supplied in 1-meter lengths, although other
exposed to the compound.
lengths are used as well. The push rods must be secured
8.2 Silicone Oil, Glycerine, or water, for use in pore water
together to bear against each other at the joints and form a
pressure measurement systems.
rigid-jointedstringofpushrods.Beforeatestiscarriedout,the
NOTE 7—Detailed comparisons and discussions on the use of these
linearityofthepushrodsshouldbechecked.Ifanyindications
fluids can be found elsewhere (8, 11).
of bending appear, the use of the rods should be suspended.
7.10.1 For the 10-cm cone steel push rods are typically
9. Hazards
36-mm outside diameter, 16-mm inside diameter, and have a
mass per unit length of 6.65 kg/m. For 15-cm cones, the test 9.1 Technical Precautions—General:
is typically performed with 44.5-mm outside diameter rods or
9.1.1 Use of components that do not meet required toler-
with standard rods used for the 10-cm cones, although other
ances or show visible signs of non-symmetric wear can result
diameters are used as well.
in erroneous cone resistance data.
9.1.2 Theapplicationofthrustinexcessofratedcapacityof
7.11 Friction Reducer—Friction reducers are normally used
the equipment can result in damage to equipment (see Section
on the push rods to reduce rod friction. If a friction reducer is
6).
used, it shall be located on the push rods no closer than 400
9.1.3 A cone sounding must not be performed any closer
mm behind the cone tip base of the 10-cm cone and 500 mm
than 10 borehole diameters from any existing unbackfilled or
behind the cone tip base of a 15-cm cone. Friction reducers,
uncased bore hole.
that increase push rod outside diameter by approximately
2 2
9.1.4 Whenperformingconepenetrationtestinginprebored
25%, are typically used for 10-cm cones. If a 15-cm cone is
holes, the depth and diameter of the prebored hole shall be
advanced with 36-mm push rods there may be no need for
reported and shown on the sounding plot.
friction reducers since the cone itself will open a larger hole.
Thetype,size,amount,andlocationoffrictionreducer(s)used
NOTE 8—Usually it is assumed that the soil is disturbed at least three
during testing must be reported.
borehole diameters below the bottom of the borehole, and this should be
taken into account when evaluating the penetration resistance data.
7.12 Thrust Machine and Reaction—The thrust machine
9.1.5 Ifobstructionsareencounteredandnormaladvanceof
will provide a continuous stroke, preferably over a distance
the sounding is stopped to bore through the obstructions, the
greater than 1 m. The thrust machine should be capable of
depth and thickness of obstructions shall be recorded.
adjusting push direction through the use of a leveling system
such that push initiates in a vertical orientation. The machine 9.1.6 Significant bending of the push rods can influence
mustadvancetheconeandpushrodsatasmooth,constantrate penetration resistance data. The use of a tubular rod guide is
D5778 − 20
recommended at the base of the thrust machine and also in removed from the fluid-filled system or pore water pressure
prebored holes to help prevent push rod bending. fluctuation during cone advancement will be incorrect due to
9.1.7 Bent push rods may result in excessive directional response lag from compression of air bubbles.
penetrometer drift and possibly unreliable penetration resis-
tance values.
10. Calibration and Standardization
9.1.8 The cone may drift directionally from vertical align-
10.1 Electronic (Piezo) Cones:
mentandthesedeviationsininclinationcancreatenonuniform
10.1.1 Newly manufactured or repaired cones are to be
loading resulting in unreliable penetration resistance data as
checked to meet the minimum calibration requirements de-
well as damage. Passing through or alongside obstructions
scribed in the annex. These calibrations include load tests,
(suchasboulders,cobbles,coarsegravel,soilconcretions,thin
thermal tests, and mechanical tests for effects of imbalanced
rock layers, or inclined dense layers) may deflect the cone and
hydrostatic forces. The calibration records must be certified as
also induce directional drift. Therefore, limitations on inclina-
correct by a registered professional engineer or other respon-
tion in the system should be imposed. Generally, a 1° change
sible engineer with knowledge and experience in materials
in inclination over 1 m of penetration can impose detrimental
testing for quality assurance.
push rod bending, while a total drift of over 15° imposes
10.1.2 Baseline Readings—Baseline or zero-load readings
non-symetricloadingandpossibleunreliablepenetrationresis-
for the load cells and pore water pressure transducers must be
tance data.
taken before and after each sounding. The baseline reading is
9.1.9 If the proper rate of advance of the cone is not
a reliable indicator of output stability, temperature-induced
maintained for the entire stroke through the measurement
apparent load, soil ingress, internal friction, threshold
interval, penetration resistance data may be erroneous.
sensitivity, and unknown loading during zero setting.
9.2 Technical Precautions—Electronic Friction Cone:
10.1.2.1 The initial baseline reading shall be taken in a
9.2.1 Failure of seals can result in damage to or inaccurate
temperature environment as close as possible to that of the
readings from electronic transducers. The seals should be
material to be sounded. If temperature is a concern, the cone
inspectedregularlyforoverallcondition,cleanliness,andwater
shall be immersed in a bucket of fresh tap water or inserted in
tightness, and replaced when necessary.
the ground to stabilize its temperature and then extracted for
9.2.2 Soil ingress between different elements of a cone can
rapid determination of initial baseline. The change in initial
result in unreliable data. Specifically, soil ingress will detri-
baseline and calibration values shall not exceed 5% FSO for
mentally affect sleeve resistance data. Seals should be in-
the load cells and pressure transducer.
spected and maintained regularly, and replaced when neces-
10.1.2.2 After a sounding is completed, a final baseline
sary. If very accurate sleeve resistance data is required, it is
reading shall be taken. The change in initial and final baseline
recommended to clean all seals after each sounding.
values shall not exceed 2% FSO for the load cells and pore
9.2.3 Electronic cones shall be temperature compensated. If
water pressure transducers.
extreme temperatures outside of the range established in
10.1.2.3 A continuous record of initial and final baselines
A1.3.1aretobeencountered,theconeshallbecheckedforthe
readings shall be kept during production testing.
required temperature range to establish it can meet the calibra-
tion requirements. Also, harsh environments may severely 10.1.2.4 Ifabaselinereadingexceedstheabovecriteria,the
affect the data acquisition system or power supplies, notebook cone shall be inspected for damage. If there is apparent
damage,theconeshallbecleanedandanydamagedpartsshall
or field computers, and other electronics.
9.2.4 Iftheshiftinbaselinereadingafterextractingthecone be replaced, after which a new baseline shall be obtained. If
this value agrees with the initial baseline within the above
from the soil is so large that the conditions of accuracy as
defined in 10.1.2.3 are no longer met, penetration resistance criteria,recalibrationisnotrequired.However,iftheinitialand
final baselines are still not within the above criteria then it is
data shall be noted as unreliable. If baseline readings do not
conform to allowable limits established by accuracy require- likely that the shift was caused by an obstacle or obstruction,
and the cone shall no longer be used until it has been repaired
ments in 10.1.2.3, the cone must be repaired, and recalibrated
or replaced. and recalibrated.
9.2.5 Friction sleeve design shall be checked in accordance
10.1.2.5 Data for a sounding where unacceptable final
with A1.6 to ensure balanced response. The response is also
baseline shift has occurred shall be reported as unreliable. In
dependent on location of water seals. If water seals are
some cases, it may be obvious where the damage occurred and
damaged during testing, and sleeve data appear affected, the
datapriortothatpointmaybeconsideredreliable.Inthatcase,
soundingdatashallbenotedasunreliableandthesealsshallbe
the location where obvious damage occurred must be clearly
repaired.
noted in the sounding logs and duly reported.
10.1.3 Cone Wear and Usage:
9.3 Technical Precautions—Piezocone:
9.3.1 The electronic piezocone measures pore water pres- 10.1.3.1 For cones used regularly, periodic calibrations
sures on the exterior of the cone by transferring the pressure should be performed. The calibration period can be based on
through a de-aired fluid system to a pressure transducer in the production footage, such as once every 3000 m of soundings,
cone interior. For proper dynamic response, the measurement or time period. If calibration equipment is not available in the
system (consisting of fluid ports and porous element) must be field, the cone may be checked in the laboratory at the end of
completely saturated prior to testing. Entrained air must be the project during which the calibration period ended.
D5778 − 20
10.1.3.2 Cones that are used infrequently should be cali- pureglycerineorsiliconemaybestoredforlongerperiods,but
brated based on a time period. If a cone has not been used for not to exceed one month after storage containers are opened
a long period of time, checking it before use is advisable. and exposed to air.
10.1.3.3 For projects requiring a high level of quality
assurance, it may be required to do a calibration before the 12. Procedure
project.
12.1 General Requirements:
10.1.3.4 Calibrations are required if an initial or a final
12.1.1 Prior to beginning a sounding, site surveys shall be
baseline reading does not meet the requirements given in
performed to ensure hazards such as overhead and under-
10.1.2.3 and whenever a cone has been repaired.
ground utilities will not be encountered. Next, the thrust
10.1.3.5 Records documenting the history of an individual
machine shall be positioned over the location of the sounding,
cone shall be maintained for evaluation of performance.
and either the leveling jacks shall be lowered to raise the
10.1.3.6 If it appears from a track record or the baseline
machine mass off the suspension system (in case the dead
readings that no significant deviations are registered, a longer
weight of the thrust machine is used to generate the required
period between calibrations can be applicable.
reaction)orthegroundanchorsshallbeplaced(incasetheyare
10.2 Calibrations of Other Sensing Devices—Other sensors used to generate the required reaction). Afterwards it shall be
ensured that the hydraulic rams of the penetrometer thrust
intheconemayrequirecalibrationsusingproceduressimilarto
those given in the annex for load cells and pressure transduc- system are set as near vertical as possible.
12.1.2 The hydraulic ram feed rate shall be set to advance
ers. The need for calibration depends on the requirements of
theindividualinvestigationprogram.Fornoncriticalprograms, theconeatarateof20 65mm/s.Thisratemustbemaintained
during the entire stroke during downward advance of the rods
the occurrence of reasonable readings may be sufficient. In
critical programs, it may be necessary to load the sensor while taking readings.
throughtherangeofinterestwithreferencestandardstoensure
NOTE 9—In practice the penetration speed is reduced whenever the
accurate readings.
recordeddataimplyaprecarioussituation(suddendramaticincreaseintip
resistance, bending, or overall inclination). Those deviations must be
clearly indicated in the report.
11. Conditioning
12.1.3 The push rods shall be checked for straightness and
11.1 Piezocones used for pore water pressure readings
permanent bending (See Section 7.10). Push rods are as-
require special preparation such that entrained air is removed
sembled and tightened by hand or by an automatic tightening
from the system. In addition the filter element should be
device, but care must be taken and threads may need cleaning
replaced after every sounding and the ports should be flushed
to ensure that the shoulders are tightly butted to prevent
after every sounding. However, for soundings where dynamic
damage to the push rods. For cones using cables, the cable is
response is important, the prepared filter elements shall be
prestrung through the push rods. A friction reducer shall be
replaced after every sounding.
added to the string of push rods as required, usually as the first
11.1.1 Fieldorlaboratorytestscanbeperformedtoevaluate
push rod behind the cone.
assembled system response, if desired by placing the cone tip
12.1.4 The cone shall be inspected before and after sound-
and the filter element in a pressurized chamber and subject
ings for damage, soil ingress, and wear. In very soft and
them to rapid pressure change. If the responses match, the
sensitive soils where accurate sleeve data is required, the cone
system is properly prepared.
shall be cleaned and lubricated in accordance with the manu-
11.1.2 To condition the filter elements, they shall be placed
facturer’s recommendations after each sounding. If damage is
in a pure glycerine or silicone oil bath under a vacuum of at
found after a sounding, this information shall be recorded.
least 90% of one atmosphere (–90 kPa). Vacuum shall be
maintained until air bubble generation is reduced to a mini- 12.2 Electronic Cones:
mum. Application of ultrasonic vibration and low heat (T < 12.2.1 The cone and the data acquisition system shall be
50°C) will assist in removal of air. Generally with use of poweredupaccordingtothemanufacturer’srecommendations.
combined vacuum, ultrasonic vibration, and low heat, filter 12.2.2 An initial baseline reading shall be obtained for the
elements can be deaired in about 4 h, although it is best to
cone in an unloaded condition at a temperature as close as
allow for 24 h to ensure best performance. Results will depend possible to ground conditions. This baseline reading shall be
upon the viscosity of the fluid and pore size of the filter
compared with the calibration values for the requirements
element. given in 10.1.2.1. If thermal stability needs to be assured, the
11.1.3 Alternatively, elements can be prepared in water by cone shall be submerged in water at temperature close to
boiling the elements while submerged in water for at least 4 h, ground; or an initial short penetration test hole shall be
although damage may result from prolongued exposure in this performed to allow the cone to reach soil temperature.
approach (4), or commercially-purchsed pre-saturated filter 12.2.3 The depth at which readings were taken shall be
elements may be used.
measured with an accuracy of at least 625 mm or 1% of the
11.1.4 Prepared elements must be kept submerged in the reading (whichever is larger) from the ground surface.
preparedfluidinclosedcontainersuntilreadyforuse,whereby 12.2.4 The cone tip resistance and friction sleeve resistance
the allowable storage length depends on the fluid. If elements shall be measured continuously with depth, and recorded at
arepreparedinwater,theymustbedeairedagainonedayafter depthintervalsnotexceeding50mm.Improvedresolutionmay
containers are opened and exposed to air. Elements stored in often be obtained at 20- or 10-mm interval readings.
D5778 − 20
12.2.5 During the sounding, the cone tip and friction sleeve deeper, the saturation levels may recover as air bubbles are
resistance shall be monitored continuously for signs of proper driven back into solution according to Boyles Law. Evaluation
operations.Itishelpfultomonitorotherindicatorssuchasram of proper interpretation of dynamic response requires experi-
pressure or inclination to ensure that damage may not occur if ence (4, 5, 8, 12). Pre-punching or pre-boring with a two-level
highly resistant layers or obstructions are encountered. Incli- phase approach to soundings may help alleviate desaturation
nation is a particularly useful indicator of imminent danger to problems.
the system (see 12.4).
12.3.4 Procedures similar
...