ASTM D4767-95
(Test Method)Standard Test Method for Consolidated Undrained Triaxial Compression Test for Cohesive Soils
Standard Test Method for Consolidated Undrained Triaxial Compression Test for Cohesive Soils
SCOPE
1.1 This test method covers the determination of strength and stress-strain relationships of a cylindrical specimen of either an undisturbed or remolded saturated cohesive soil. Specimens are isotropically consolidated and sheared in compression without drainage at a constant rate of axial deformation (strain controlled).
1.2 This test method provides for the calculation of total and effective stresses, and axial compression by measurement of axial load, axial deformation, and pore-water pressure.
1.3 This test method provides data useful in determining strength and deformation properties of cohesive soils such as Mohr strength envelopes and Young's modulus. Generally, three specimens are tested at different effective consolidation stresses to define a strength envelope.
1.4 The determination of strength envelopes and the development of relationships to aid in interpreting and evaluating test results are beyond the scope of this test method and must be performed by a qualified, experienced professional.
1.5 The values stated in SI units shall be regarded as the standard. The values stated in inch-pound units are approximate.
1.6 This standard may involve hazardous materials, operations, and equipment. 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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: D 4767 – 95
Standard Test Method for
Consolidated Undrained Triaxial Compression Test for
Cohesive Soils
This standard is issued under the fixed designation D 4767; 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.
1. Scope * D 1587 Practice for Thin-Walled Tube Sampling of Soils
D 2166 Test Method for Unconfined Compressive Strength
1.1 This test method covers the determination of strength
of Cohesive Soil
and stress-strain relationships of a cylindrical specimen of
D 2216 Method for Laboratory Determination of Water
either an undisturbed or remolded saturated cohesive soil.
(Moisture) Content of Soil, Rock, and Soil-Aggregate
Specimens are isotropically consolidated and sheared in com-
Mixtures
pression without drainage at a constant rate of axial deforma-
D 2435 Test Method for One-Dimensional Consolidation
tion (strain controlled).
Properties of Soils
1.2 This test method provides for the calculation of total and
D 2487 Test Method for Classification of Soils for Engi-
effective stresses, and axial compression by measurement of
neering Purposes
axial load, axial deformation, and pore-water pressure.
D 2850 Test Method for Unconsolidated, Undrained Com-
1.3 This test method provides data useful in determining
pressive Strength of Cohesive Soils in Triaxial Compres-
strength and deformation properties of cohesive soils such as
sion
Mohr strength envelopes and Young’s modulus. Generally,
D 3740 Practice for Minimum Requirements for Agencies
three specimens are tested at different effective consolidation
Engaged in the Testing and/or Inspection of Soil and Rock
stresses to define a strength envelope.
as Used in Engineering Design and Construction
1.4 The determination of strength envelopes and the devel-
D 4220 Practices for Preserving and Transporting Soil
opment of relationships to aid in interpreting and evaluating
Samples
test results are beyond the scope of this test method and must
D 4318 Test Method for Liquid Limit, Plastic Limit, and
be performed by a qualified, experienced professional.
Plasticity Index of Soils
1.5 The values stated in SI units shall be regarded as the
D 4753 Specification for Evaluating, Selecting, and Speci-
standard. The values stated in inch-pound units are approxi-
fying Balances and Scales for Use in Soil and Rock
mate.
Testing
1.6 This standard may involve hazardous materials, opera-
tions, and equipment. This standard does not purport to
3. Terminology
address all of the safety concerns, if any, associated with its
3.1 Definitions—The definitions of terms used in this test
use. It is the responsibility of the user of this standard to
method shall be in accordance with Terminology D 653.
establish appropriate safety and health practices and deter-
3.2 Definitions of Terms Specific to This Standard:
mine the applicability of regulatory limitations prior to use.
3.2.1 back pressure—a pressure applied to the specimen
2. Referenced Documents pore-water to cause air in the pore space to compress and to
pass into solution in the pore-water thereby increasing the
2.1 ASTM Standards:
percent saturation of the specimen.
D 422 Method for Particle-Size Analysis of Soils
3.2.2 effective consolidation stress—the difference between
D 653 Terminology Relating to Soil, Rock, and Contained
the cell pressure and the pore-water pressure prior to shearing
Fluids
2 the specimen.
D 854 Test Method for Specific Gravity of Soils
3.2.3 failure—the stress condition at failure for a test
specimen. Failure is often taken to correspond to the maximum
principal stress difference (maximum deviator stress) attained
This test method is under the jurisdiction of ASTM Committee D-18 on Soil
and Rock and is the direct responsibility of Subcommittee D18.05 on Strength and
or the principal stress difference (deviator stress) at 15 % axial
Compressibility of Soils.
strain, whichever is obtained first during the performance of a
Current edition approved Dec. 10, 1995. Published April 1996. Originally
e1 e1 test. Depending on soil behavior and field application, other
published as D 4767 – 88 . Last previous edition D 4767 – 88 .
Annual Book of ASTM Standards, Vol 04.08. suitable failure criteria may be defined, such as maximum
*A Summary of Changes section appears at the end of this standard.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4767
effective stress obliquity, s81/s83, or the principal stress of the accuracy prescribed in this paragraph and may be a part
difference (deviator stress) at a selected axial strain other than of the axial loading device. The axial load-measuring device
15 %. shall be capable of measuring the axial load to an accuracy of
within 1 % of the axial load at failure. If the load-measuring
4. Significance and Use
device is located inside the triaxial compression chamber, it
4.1 The shear strength of a saturated soil in triaxial com-
shall be insensitive to horizontal forces and to the magnitude of
pression depends on the stresses applied, time of consolidation,
the chamber pressure.
strain rate, and the stress history experienced by the soil.
5.4 Triaxial Compression Chamber—The triaxial chamber
4.2 In this test method, the shear characteristics are mea-
shall have a working chamber pressure equal to the sum of the
sured under undrained conditions and is applicable to field
effective consolidation stress and the back pressure. It shall
conditions where soils that have been fully consolidated under
consist of a top plate and a base plate separated by a cylinder.
one set of stresses are subjected to a change in stress without
The cylinder may be constructed of any material capable of
time for further consolidation to take place (undrained condi-
withstanding the applied pressures. It is desirable to use a
tion), and the field stress conditions are similar to those in the
transparent material or have a cylinder provided with viewing
test method.
ports so the behavior of the specimen may be observed. The top
NOTE 1—If the strength is required for the case where the soil is not plate shall have a vent valve such that air can be forced out of
consolidated during testing prior to shear, refer to Test Method D 2850 or
the chamber as it is filled. The baseplate shall have an inlet
Test Method D 2166.
through which the pressure liquid is supplied to the chamber,
and inlets leading to the specimen base and provide for
4.3 Using the pore-water pressure measured during the test,
the shear strength determined from this test method can be connection to the cap to allow saturation and drainage of the
expressed in terms of effective stress. This shear strength may specimen when required.
be applied to field conditions where full drainage can occur 5.5 Axial Load Piston—The piston passing through the top
(drained conditions) or where pore pressures induced by
of the chamber and its seal must be designed so the variation
loading can be estimated, and the field stress conditions are in axial load due to friction does not exceed 0.1 % of the axial
similar to those in the test method.
load at failure and so there is negligible lateral bending of the
4.4 The shear strength determined from the test expressed in piston during loading.
terms of total stresses (undrained conditions) or effective
NOTE 4—The use of two linear ball bushings to guide the piston is
stresses (drained conditions) is commonly used in embankment
recommended to minimize friction and maintain alignment.
stability analyses, earth pressure calculations, and foundation
NOTE 5—A minimum piston diameter of ⁄6the specimen diameter has
design.
been used successfully in many laboratories to minimize lateral bending.
NOTE 2—Notwithstanding the statements on precision and bias con-
5.6 Pressure and Vacuum-Control Devices—The chamber
tained in this test method. The precision of this test method is dependent
pressure and back pressure control devices shall be capable of
on the competence of the personnel performing it and the suitability of the
applying and controlling pressures to within 62 kPa (0.25
equipment and facilities used. Agencies which meet the criteria of Practice
lb/in. ) for effective consolidation pressures less than 200 kPa
D 3740 are generally considered capable of competent testing. Users of
(28 lb/in. ) and to within 61 % for effective consolidation
this test method are cautioned that compliance with Practice D 3740 does
not ensure reliable testing. Reliable testing depends on several factors;
pressures greater than 200 kPa. The vacuum-control device
Practice D 3740 provides a means of evaluating some of those factors.
shall be capable of applying and controlling partial vacuums to
within 62 kPa. The devices may consist of self-compensating
5. Apparatus
mercury pots, pneumatic pressure regulators, combination
5.1 The requirements for equipment needed to perform
pneumatic pressure and vacuum regulators, or any other device
satisfactory tests are given in the following sections.
capable of applying and controlling pressures or partial vacu-
5.2 Axial Loading Device—The axial loading device may
ums to the required tolerances. These tests can require a test
be a screw jack driven by an electric motor through a geared
duration of several days, therefore, an air/water interface is not
transmission, a hydraulic loading device, or any other com-
recommended for either the chamber pressure or back pressure
pression device with sufficient capacity and control to provide
systems.
the rate of axial strain (loading) prescribed in 8.4.2. The rate of
5.7 Pressure- and Vacuum-Measurement Devices—The
advance of the loading device should not deviate by more than
chamber pressure-, back pressure-, and vacuum-measuring
61 % from the selected value. Vibration due to the operation
devices shall be capable of measuring pressures or partial
of the loading device shall be sufficiently small to not cause
vacuums to the tolerances given in 5.6. They may consist of
dimensional changes in the specimen or to produce changes in
Bourdon gages, pressure manometers, electronic pressure
pore-water pressure when the drainage valves are closed.
transducers, or any other device capable of measuring pres-
sures, or partial vacuums to the stated tolerances. If separate
NOTE 3—A loading device may be judged to produce sufficiently small
vibrations if there are no visible ripples in a glass of water placed on the devices are used to measure the chamber pressure and back
loading platform when the device is operating at the speed at which the
pressure, the devices must be calibrated simultaneously and
test is performed.
against the same pressure source. Since the chamber and back
5.3 Axial Load-Measuring Device—The axial load- pressure are the pressures taken at the mid-height of the
measuring device shall be a load ring, electronic load cell, specimen, it may be necessary to adjust the calibration of the
hydraulic load cell, or any other load-measuring device capable devices to reflect the hydraulic head of fluids in the chamber
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4767
and back pressure control systems. prevent lateral motion or tilting, and the specimen cap shall be
designed such that eccentricity of the piston-to-cap contact
5.8 Pore-Water Pressure-Measurement Device—The speci-
relative to the vertical axis of the specimen does not exceed 1.3
men pore-water pressure shall also be measured to the toler-
mm (0.05 in.). The end of the piston and specimen cap contact
ances given in 5.6. During undrained shear, the pore-water
area shall be designed so that tilting of the specimen cap during
pressure shall be measured in such a manner that as little water
the test is minimal. The cylindrical surface of the specimen
as possible is allowed to go into or out of the specimen. To
base and cap that contacts the membrane to form a seal shall be
achieve this requirement, a very stiff electronic pressure
smooth and free of scratches.
transducer or null-indicating device must be used. With an
5.12 Porous Discs—Two rigid porous disks shall be used to
electronic pressure transducer the pore-water pressure is read
provide drainage at the ends of the specimen. The coefficient of
directly. With a null-indicating device a pressure control is
permeability of the disks shall be approximately equal to that
continuously adjusted to maintain a constant level of the
−4 −5
of fine sand (1 3 10 cm/s (4 3 10 in./s)). The disks shall
water/mercury interface in the capillary bore of the device. The
be regularly cleaned by ultrasonic or boiling and brushing and
pressure required to prevent movement of the water is equal to
checked to determine whether they have become clogged.
the pore-water pressure. Both measuring devices shall have a
5.13 Filter-Paper Strips and Disks— Filter-paper strips are
compliance of all the assembled parts of the pore-water
used by many laboratories to decrease the time required for
pressure-measurement system relative to the total volume of
testing. Filter-paper disks of a diameter equal to that of the
the specimen, satisfying the following requirement:
specimen may be placed between the porous disks and speci-
–6 2 –5 2
~DV/V!/Du < 3.2 3 10 m /kN ~2.2 3 10 in. /lb! (1)
men to avoid clogging of the porous disks. If filter strips or
disks are used, they shall be of a type that does not dissolve in
where:
water. The coefficient of permeability of the filter paper shall
DV = change in volume of the pore-water measurement
−5 −6
3 3
not be less than 1 3 10 cm/s (4 3 10 cm/s) for a normal
system due to a pore pressure change, mm (in. ),
3 3
pressure of 550 kPa (80 lb/in. ). To avoid hoop tension, filter
V = total volume of the specimen, mm (in. ), and
Du = change in pore pressure, kPa (lb/in. ). strips should cover no more than 50 % of the specimen
periphery. Filter-strip cages have been successfully used by
NOTE 6—To meet the compliance requirement, tubing between the
many laboratories. An equation for correcting the principal
specimen and the measuring device should be short and thick-walled with
stress difference (deviator stress) for the effect of the stre
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