ASTM D3441-98
(Test Method)Standard Test Method for Mechanical Cone Penetration Tests of Soil
Standard Test Method for Mechanical Cone Penetration Tests of Soil
SCOPE
1.1 This test method covers the determination of end bearing and side friction, the components of penetration resistance which are developed during the steady slow penetration of a pointed rod into soil. This test method is sometimes referred to as the "Dutch Cone Test," or "Cone Penetration Test" and is often abbreviated as the "CPT."
1.2 This test method includes the use of both cone and friction-cone penetrometers, of both the mechanical and electric types. It does not include data interpretation. It also includes the penetrometer aspects of piezocone soundings, but does not include the details of piezometer construction, location, measurement, or data interpretation. Note 1-The European Standard for the CPT uses a tip of right cylindrical shape as shown in Fig. 3, as their reference test against which other CPTs may be compared.
1.3 Mechanical penetrometers of the type described in this test method operate incrementally, using a telescoping penetrometer tip, resulting in no movement of the push rods during the measurement of the resistance components. Design constraints for mechanical penetrometers preclude a complete separation of the end-bearing and side-friction components. Electric penetrometers are advanced continuously and permit separate measurement of both components. Differences in shape and method of advance between cone penetrometer tips may result in significant differences in one or both resistance components.
1.4 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D3441–98
Standard Test Method for
Mechanical Cone Penetration Tests of Soil
This standard is issued under the fixed designation D 3441; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope ISOPT-1 International Reference Test Procedure for the
Cone Penetration Test (CPT)
1.1 This test method covers the determination of end bear-
ing and side friction, the components of penetration resistance
3. Terminology
that are developed during the steady slow penetration of a
3.1 Definitions:
pointed rod into soil. This test method is sometimes referred to
3.1.1 cone, n—the cone-shaped point of the penetrometer
as the Dutch Cone Test or Cone Penetration Test and is often
tip, upon which the end-bearing resistance develops.
abbreviated as CPT.
3.1.2 cone penetrometer, n—an instrument in the form of a
1.2 This test method includes the use of mechanical cone
cylindrical rod with a conical point designed for penetrating
and friction-cone penetrometers. It does not include the use of
soil and soft rock and for measuring the end-bearing compo-
electric and electronic cones or data interpretation.
nent of penetration resistance.
1.2.1 The use of electric and electronic cones is covered in
3.1.3 cone resistance, or end-bearing resistance q,n—the
c
Test Method D 5778.
resistance to penetration developed by the cone equal to the
1.3 Mechanical penetrometers of the type described in this
vertical force applied to the cone divided by its horizontally
test method operate incrementally, using a telescoping pen-
projected area.
etrometertip,resultinginnomovementofthepushrodsduring
3.1.4 cone sounding, n—theentireseriesofpenetrationtests
the measurement of the resistance components. Design con-
performed at one location when using a cone penetrometer.
straints for mechanical penetrometers preclude a complete
3.1.5 friction-cone penetrometer, n—a cone penetrometer
separation of the end-bearing and side-friction components.
with the additional capability of measuring the local side
1.4 The values stated in inch-pound units are to be regarded
friction component of penetration resistance.
as the standard. The values given in parentheses are provided
3.1.6 friction cone sounding, n—theentireseriesofpenetra-
for information only.
tion tests performed at one location when using a friction cone
1.5 This standard does not purport to address all of the
penetrometer.
safety concerns, if any, associated with its use. It is the
3.1.7 friction ratio, R, n—the ratio of friction resistance to
f
responsibility of the user of this standard to establish appro-
cone resistance, f /q , expressed in percent.
s c
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
NOTE 1—The friction ratio for mechanical penetrometers is not com-
parable to the friction ratio measured by electronic or electrical penetrom-
2. Referenced Documents
eter (Test Method D 5778). Users should verify that the application of
empiricalcorrelationssuchasthosepredictingsoiltypefrom R areforthe
f
2.1 ASTM Standards:
correct penetrometer.
D 653 Terminology Relating to Soil, Rock, and Contained
3.1.8 friction resistance, f , n—the resistance to penetration
Fluids
s
D 5778 Test Method for Performing Electronic Friction developed by the friction sleeve, equal to the vertical force
appliedtothesleevedividedbyitssurfacearea.Thisresistance
Cone and Piezocone Penetration Testing of Soil
2.2 Other Standards: consists of the sum of friction and adhesion.
3.1.9 friction sleeve, n—a section of the penetrometer tip
USBR D 7020 Performing Cone Penetration Testing of
Soils-Mechanical Method upon which the local side-friction resistance develops.
3.1.10 inner rods, n—rods that slide inside the push rods to
extend the tip of a mechanical penetrometer.
This test method is under the jurisdiction of Committee D-18 on Soil and Rock
3.1.11 mechanical penetrometer, n—a penetrometer that
and is the direct responsibility of Subcommittee D18.02 on Sampling and Related
uses a set of inner rods to operate a telescoping penetrometer
Field Testing for Soil Investigations.
Current edition approved May 10, 1998. Published January 1999. Originally
published as D 3441 – 75 T. Last previous edition D 3441 – 94.
2 3
Earth Manual, Part II, Third Edition, U.S. Department of the Interior, Bureau Proceedings of the First International Symposium for Penetration Testing,
of Reclamation, U.S. Government Printing Office, 1990. DeRuiter, ed., Blakema, Rotterdam, ISBN 90 6191 8014, 1988.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D3441–98
tip and to transmit the component(s) of penetration resistance tween inner rods and push rods shall be between 0.020 and
to the surface for measurement. 0.040 in. (0.5 and 1.0 mm) (see 7.8.1).
3.1.12 penetrometer tip, n—the end section of the pen- 5.1.6 Measurement Accuracy—Maintain the trust-
etrometer, which comprises the active elements that sense the measuring instrumentation to obtain trust measurements within
soil resistance, the cone, and in the case of the friction-cone 65 % of the correct values. Measurement equipment (see
penetrometer, the friction sleeve. 5.2.5) should be subjected to calibration at regularly scheduled
intervals such as annually or after a specified amount of
3.1.13 push rods, n—the thick-walled tubes, or other suit-
able rods, used for advancing the penetrometer tip to the accumulated testing. Examples of mechanical cone testing
calibration can be found in USBR D 7020 and ISOPT-1.
required test depth.
NOTE 2—Special, and preferably redundant, instrumentation may be
4. Significance and Use
required in the offshore environment to ensure this accuracy and the
proper operation of all the remote systems involved.
4.1 This test method supplies data on selected engineering
properties of soil intended to help with design and construction
5.2 Mechanical Penetrometers:
of earthworks and the foundations for structures.
5.2.1 The sliding mechanism necessary in a mechanical
4.2 This test method tests the soil in place and does not
penetrometer tip must allow a downward movement of the
obtain soil samples. The interpretation of the results from this
cone in relation to the push rods of at least 1.2 in. (30.5 mm).
test method requires knowledge of the types of soil penetrated.
NOTE 3—At certain combinations of depth and tip resistance(s), the
Engineers usually obtain this soil information from parallel
elastic compression of the inner rods may exceed the downward stroke
borings and soil sampling methods, but prior information or
that the trust machine can apply to the inner rods relative to the push rods.
experience may preclude the need for borings.
In this case, the tip will not extend and the trust readings will rise
4.3 Engineers often correlate the results of tests by this test elastically to the end of the machine stroke and then jump abruptly when
the trust machine makes contact with the push rods.
method with laboratory or other types of field tests or directly
with performance. The accuracy of such correlations will vary
5.2.2 Mechanical penetrometer tip design shall include
with the type of soil involved. Engineers usually rely on local
protection against soil entering the sliding mechanism and
experience to judge this accuracy.
affecting the resistance component(s) (see 5.2.3 and Note 3).
5.2.3 Cone Penetrometer—Fig. 1 shows the design and
5. Apparatus
action of one mechanical cone penetrometer tip. A mantle of
reduced diameter is attached above the cone to minimize
5.1 General:
possible soil contamination of the sliding mechanism.
5.1.1 Cone—The cone shall have 60°(65°) point angle and
abasediameterof1.40660.016in.(35.7 60.4mm),resulting
NOTE 4—An unknown amount of side friction may develop along this
2 2
in a projected area of 1.55 in. (10 cm ). The point of the cone
mantle and be included in the cone resistance.
shall have a radius less than ⁄8 in. (3 mm).
5.2.4 Friction Cone Penetrometer—Fig. 2 shows the design
5.1.2 Friction Sleeve—having the same outside diameter
and action of one telescoping mechanical friction cone pen-
+0.024 to –0.000 in. (+0.5 to –0.0 mm) as the base diameter of
etrometer tip. The lower part of the tip, including a mantle to
the cone (see 5.1.1). No other part of the penetrometer tip shall
which the cone attaches, advances first until the flange engages
project outside the sleeve diameter. The surface area of the
the friction sleeve and then both advance.
2 2
sleeve shall be 23.2 in. (150 cm ) 62%.
5.1.3 Steel—The cone and friction sleeve shall be made
from steel of a type and hardness suitable to resist wear due to
abrasion by soil. The friction sleeve shall have and maintain
with use a roughness of 63 µin. (1.6 µm) AA, 650 %.
5.1.4 Push Rods—Made of suitable steel, these rods must
have a section adequate to sustain without buckling, the thrust
required to advance the penetrometer tip. They must have an
outsidediameternotgreaterthanthediameterofthebaseofthe
cone for a length of at least 1.3 ft (0.4m) above the base, or, in
thecaseofthefriction-conepenetrometer,atleast1.0ft(0.3m)
above the top of the friction sleeve. Each push rod must have
the same constant inside diameter. They must screw or attach
together to bear against each other and form a rigid-jointed
string of rods with a continuous, straight axis.
5.1.5 Inner Rods—Mechanical penetrometers require a
separate set of steel or other metal alloy inner rods within the
steel push rods. The inner rods must have a constant outside
diameter with a roughness less than 125 µin. (3.2 µm) AA.
They must have the same length as the push rods (6 0.004 in.
or 6 0.1 mm) and a cross section adequate to transmit the cone
FIG. 1 Example of a Mechanical Cone Penetrometer Tip (Dutch
resistance without buckling or other damage. Clearance be- Mantle Cone)
D3441–98
friction-cone penetrometer.The rate of 4 ft/min (20 m/s) is suitable for the
single resistance reading required when using the mechanical cone
penetrometers. The European standard requires 4 ft/min (20 mm/s).
6.2 Mechanical Penetrometers:
6.2.1 Cone Penetrometers—(1) Advance penetrometer tip
to the required test depth by applying sufficient thrust on the
push rods, and (2) Apply sufficient thrust on the inner rods to
extend the penetrometer tip (see Fig. 1). Obtain the cone
resistance at a specific point (see 6.2.3) during the downward
movement of the inner rods relative to the stationary push rods.
Repeat step (1). Apply sufficient thrust on the push rods to
collapse the extended tip and advance it to a new test depth. By
continually repeating this two-step cycle, obtain cone resis-
tance data at increments of depth. This increment shall not
ordinarily exceed 8 in. (203 mm).
6.2.2 Friction-Cone Penetrometer—Use the procedure as
described in 6.2.1, but obtain two resistances during step (2)
extension of the tip (see Fig. 2). First obtain the cone resistance
during the initial phase of the extension. When the lower part
of the tip engages and pulls down the friction sleeve, obtain a
second measurement of the total resistance of the cone plus the
sleeve. Subtraction gives the sleeve resistance.
NOTE 9—Because of soil layering, the cone resistance may change
duringtheadditionaldownwardmovementofthetiprequiredtoobtainthe
friction measurement.
NOTE 10—The soil friction along the sleeve puts an additional over-
burden load on the soil above the cone and may increase cone resistance
FIG. 2 Example of a Mechanical Friction-Cone Penetrometer Tip
above that measured during the initial phase of the tip extension by an
(Begemann Friction-Cone)
unknown but probably small amount. Ignore this effect.
6.2.3 Recording Data—To obtain reproducible cone-
NOTE 5—The shoulder at the lower end of the friction sleeve encoun-
resistance test data, or cone and friction-resistance test data,
ters end-bearing resistance. In sand, as much as two thirds of the sleeve
when using a friction-cone tip, record only those thrust
resistancemayconsistofbearingonthisshoulder.Ignorethiseffectinsoft
readings that occur at a well-defined point during the down-
to medium clays.
ward movement of the top of the inner rods in relation to the
5.2.5 Measuring Equipment—Measure the penetration re-
top of the push rods. Because of the elastic compression of
sistance(s) at the surface by a suitable device such as a
inner rods (see Note 2), this point ordinarily should be at not
hydraulic or electric load cell or proving ring.
less than 1.0 in. (25 mm) apparent relative movement of the
5.3 Thrust Machine—This machine shall provide a continu-
inner rods. When using the friction-cone penetrometer, this
ous stroke, preferably over a distance greater than one push rod
point shall be just before the cone engages the friction sleeve.
length. The machine must advance the penetrometer tip at a
NOTE 11—Fig. 3 shows one example of how the thrust in the hydraulic
constant rate while the magnitude of the thrust required
load cell can vary during the extension of the friction-cone tip. Note the
fluctuates (see 6.1.2).
jump in gage pressure when the cone engages the sleeve.
NOTE 6—Deep penetration soundings usually require a thrust capacity
6.2.3.1 Obtain the cone plus friction-resistance reading as
of at least 5 tons (45kN). Most modern machines use hydraulic pistons
soon as possible after the jump so as to minimize the error
with 10 to 20-ton (90 to 180-kN) thrust capability.
described in Fig. 3. Unless using continuous recording as in
5.4 Reaction Equipment—The proper performance of the
Fig. 3, the operator should not record a cone plus friction
static-thrust machine requires a stable, static reaction.
resistance if he suspects the cone resistance is changing
abruptly or erratically.
NOTE 7—The type of reaction provided may affect the penetrometer
resistance(s) measured, particularly in the surface or near-surface layers.
7. Special Techniques and Precautions
6. Procedure
7.1 Reduction of Friction Along Push Rods—The purpose
6.1 General:
of this friction reduction is to increase the penetrometer depth
6.1.1 Set up the thrust machine for a thrust direction as near
capability,andnottoreduceanydifferencesbetweenresistance
vertical as practical.
components determined by mechanical tips as noted in 1.3. To
6.1.2 Rate of Penetration—Maintain a rate of depth pen-
accompli
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