ASTM D5311-92(1996)
(Test Method)Standard Test Method for Load Controlled Cyclic Triaxial Strength of Soil
Standard Test Method for Load Controlled Cyclic Triaxial Strength of Soil
SCOPE
1.1 This test method covers the determination of the cyclic strength (sometimes called the liquefaction potential) of saturated soils in either undisturbed or reconstituted states by the load-controlled cyclic triaxial technique.
1.2 The cyclic strength of a soil is evaluated relative to a number of factors, including: the development of axial strain, magnitude of applied cyclic stress, number of cycles of stress application, development of excess pore-water pressure, and state of effective stress. A comprehensive review of factors affecting cyclic triaxial test results is contained in the literature (1).
1.3 Cyclic triaxial strength tests are conducted under undrained conditions to simulate essentially undrained field conditions during earthquake or other cyclic loading.
1.4 Cyclic triaxial strength tests are destructive. Failure may be defined on the basis of the number of stress cycles required to reach a limiting strain or 100% pore pressure ratio. See Section 3 for Terminology.
1.5 This test method is generally applicable for testing cohesionless free draining soils of relatively high permeability. When testing well-graded materials, silts, or clays, it should be recognized that pore-water pressures monitored at the specimen ends to not in general represent pore-water pressure values throughout the specimen. However, this test method may be followed when testing most soil types if care is taken to ensure that problem soils receive special consideration when tested and when test results are evaluated.
1.6 There are certain limitations inherent in using cyclic triaxial tests to simulate the stress and strain conditions of a soil element in the field during an earthquake.
1.6.1 Nonuniform stress conditions within the test specimen are imposed by the specimen end platens. This can cause a redistribution of void ratio within the specimen during the test.
1.6.2 A 90° change in the direction of the major principal stress occurs during the two halves of the loading cycle on isotropically consolidated specimens.
1.6.3 The maximum cyclic shear stress that can be applied to the specimen is controlled by the stress conditions at the end of consolidation and the pore-water pressures generated during testing. For an isotropically consolidated contractive (volume decreasing) specimen tested in cyclic compression, the maximum cyclic shear stress that can be applied to the specimen is equal to one-half of the initial total axial pressure. Since cohesionless soils are not capable of taking tension, cyclic shear stresses greater than this value tend to lift the top platen from the soil specimen. Also, as the pore-water pressure increases during tests performed on isotropically consolidated specimens, the effective confining pressure is reduced, contributing to the tendency of the specimen to neck during the extension portion of the load cycle, invalidating test results beyond that point.
1.6.4 While it is advised that the best possible undisturbed specimens be obtained for cyclic strength testing, it is sometimes necessary to reconstitute soil specimens. It has been shown that different methods of reconstituting specimens to the same density may result in significantly different cyclic strengths. Also, undisturbed specimens will almost always be stronger than reconstituted specimens.
1.6.5 The interaction between the specimen, membrane, and confining fluid has an influence on cyclic behavior. Membrane compliance effects cannot be readily accounted for in the test procedure or in interpretation of test results. Changes in pore-water pressure can cause changes in membrane penetration in specimens of cohesionless soils. These changes can significantly influence the test results.
1.6.6 The mean total confining pressure is asymmetric during the compression and extension stress application when the chamber pressure is constant. This is totally different from the symmetric stress in the simple shear case...
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Designation: D 5311 – 92 (Reapproved 1996)
Standard Test Method for
Load Controlled Cyclic Triaxial Strength of Soil
This standard is issued under the fixed designation D 5311; 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 1.6.2 A 90° change in the direction of the major principal
stress occurs during the two halves of the loading cycle on
1.1 This test method covers the determination of the cyclic
isotropically consolidated specimens.
strength (sometimes called the liquefaction potential) of satu-
1.6.3 The maximum cyclic shear stress that can be applied
rated soils in either undisturbed or reconstituted states by the
to the specimen is controlled by the stress conditions at the end
load-controlled cyclic triaxial technique.
of consolidation and the pore-water pressures generated during
1.2 The cyclic strength of a soil is evaluated relative to a
testing. For an isotropically consolidated contractive (volume
number of factors, including: the development of axial strain,
decreasing) specimen tested in cyclic compression, the maxi-
magnitude of applied cyclic stress, number of cycles of stress
mum cyclic shear stress that can be applied to the specimen is
application, development of excess pore-water pressure, and
equal to one-half of the initial total axial pressure. Since
state of effective stress. A comprehensive review of factors
cohesionless soils are not capable of taking tension, cyclic
affecting cyclic triaxial test results is contained in the literature
2 shear stresses greater than this value tend to lift the top platen
(1).
from the soil specimen. Also, as the pore-water pressure
1.3 Cyclic triaxial strength tests are conducted under und-
increases during tests performed on isotropically consolidated
rained conditions to simulate essentially undrained field con-
specimens, the effective confining pressure is reduced, contrib-
ditions during earthquake or other cyclic loading.
uting to the tendency of the specimen to neck during the
1.4 Cyclic triaxial strength tests are destructive. Failure may
extension portion of the load cycle, invalidating test results
be defined on the basis of the number of stress cycles required
beyond that point.
to reach a limiting strain or 100 % pore pressure ratio. See
1.6.4 While it is advised that the best possible undisturbed
Section 3 for Terminology.
specimens be obtained for cyclic strength testing, it is some-
1.5 This test method is generally applicable for testing
times necessary to reconstitute soil specimens. It has been
cohesionless free draining soils of relatively high permeability.
shown that different methods of reconstituting specimens to the
When testing well-graded materials, silts, or clays, it should be
same density may result in significantly different cyclic
recognized that pore-water pressures monitored at the speci-
strengths. Also, undisturbed specimens will almost always be
men ends to not in general represent pore-water pressure values
stronger than reconstituted specimens.
throughout the specimen. However, this test method may be
1.6.5 The interaction between the specimen, membrane, and
followed when testing most soil types if care is taken to ensure
confining fluid has an influence on cyclic behavior. Membrane
that problem soils receive special consideration when tested
compliance effects cannot be readily accounted for in the test
and when test results are evaluated.
procedure or in interpretation of test results. Changes in
1.6 There are certain limitations inherent in using cyclic
pore-water pressure can cause changes in membrane penetra-
triaxial tests to simulate the stress and strain conditions of a soil
tion in specimens of cohesionless soils. These changes can
element in the field during an earthquake.
significantly influence the test results.
1.6.1 Nonuniform stress conditions within the test specimen
1.6.6 The mean total confining pressure is asymmetric
are imposed by the specimen end platens. This can cause a
during the compression and extension stress application when
redistribution of void ratio within the specimen during the test.
the chamber pressure is constant. This is totally different from
the symmetric stress in the simple shear case of the level
This test method is under the jurisdiction of ASTM Committee D-18 on Soil ground liquefaction.
and Rock and is the direct responsibility of Subcommittee D18.09 on Dynamic
1.7 The values stated in both inch-pound and SI units are to
Properties of Soils.
be regarded separately as the standard. The values given in
Current edition approved Oct. 15, 1992. Published January 1993.
parentheses are for information only.
The boldface numbers in parentheses refer to a list of references at the end of
the text.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5311
1.8 This standard does not purport to address all of the 3.2.2 peak pore pressure ratio—the maximum pore pressure
safety concerns, if any, associated with its use. It is the ratio measured during a particular loading sequence.
responsibility of the user of this standard to establish appro- 3.2.3 peak (single amplitude) strain—the maximum axial
priate safety and health practices and determine the applica- strain (from the origin or initial step) in either compression or
bility of regulatory limitations prior to use. extension produced during a particular loading sequence.
3.2.4 peak to peak (double amplitude) strain— the differ-
2. Referenced Documents
ence between the maximum axial strain in compression and
extension during a given cycle under cyclic loading conditions.
2.1 ASTM Standards:
3.2.5 pore pressure ratio—the ratio, expressed as a percent-
D 422 Test Method for Particle-Size Analysis of Soils
age, of the change of excess pore-water pressure, D u,tothe
D 653 Terminology Relating to Soil, Rock, and Contained
effective minor principal stress, s8 , at the end of primary
Fluids 3c
consolidation.
D 854 Test Method for Specific Gravity of Soils
D 1587 Practice for Thin-Walled Tube Sampling of Soils
4. Summary of Test Method
D 2216 Test Method for Laboratory Determination of Water
4.1 A cylindrical soil specimen is sealed in a watertight
(Moisture) Content of Soil and Rock
rubber membrane and confined in a triaxial chamber where it
D 2850 Test Method for Unconsolidated, Undrained Com-
is subjected to a confining pressure. An axial load is applied to
pressive Strength of Cohesive Soils in Triaxial Compres-
the top of the specimen by a load rod.
sion
4.2 Specimens are consolidated isotropically (equal axial
D 4220 Practice for Preserving and Transporting Soil
and radial stress). Tubing connections to the top and bottom
Samples
specimen platens permit flow of water during saturation,
D 4253 Test Methods for Maximum Index Density and Unit
consolidation and measurement of pore-water pressure during
Weight of Soils Using a Vibratory Table
cyclic loading.
D 4254 Test Method for Minimum Index Density and Unit
4.3 Following saturation and consolidation, the specimen is
Weight of Soils and Calculation of Relative Density
subjected to a sinusoidally varying axial load by means of the
D 4318 Test Method for Liquid Limit, Plastic Limit, and
load rod connected to the specimen top platen. The cyclic load,
Plasticity Index of Soils
specimen axial deformation, and porewater pressure develop-
D 4767 Test Method for Consolidated-Undrained Triaxial
ment with time are monitored.
Compression Test on Cohesive Soils
4.4 The test is conducted under undrained conditions to
approximate essentially undrained field conditions during
3. Terminology
earthquake or other dynamic loading. The cyclic loading
3.1 Definitions:
generally causes an increase in the pore-water pressure in the
3.1.1 Definitions for terms used in this test method (includ-
specimen, resulting in a decrease in the effective stress and an
ing liquefaction) are in accordance with Terminology D 653.
increase in the cyclic axial deformation of the specimen.
Additional descriptions of terms are defined in 3.2 and in 10.2
4.5 Failure may be defined as when the peak excess pore-
and Fig. 1.
water pressure equals the initial effective confining pressure,
3.2 Definitions of Terms Specific to This Standard:
full or 100 % pore pressure ratio (sometimes called initial
3.2.1 full or 100 % pore pressure ratio— a condition in
liquefaction), or in terms of a limiting cyclic strain or perma-
which Du equals s8 .
3c
nent strain.
5. Significance and Use
5.1 Cyclic triaxial strength test results are used for evaluat-
Annual Book of ASTM Standards, Vol 04.08.
ing the ability of a soil to resist the shear stresses induced in a
soil mass due to earthquake or other cyclic loading.
5.1.1 Cyclic triaxial strength tests may be performed at
different values of effective confining pressure on isotropically
consolidated specimens to provide data required for estimating
the cyclic stability of a soil.
5.1.2 Cyclic triaxial strength tests may be performed at a
single effective confining pressure, usually equal to 14.5 lb/in.
2(100 kN/m ), or alternate pressures as appropriate on isotro-
pically consolidated specimens to compare cyclic strength
results for a particular soil type with that of other soils, Ref (2).
5.2 The cyclic triaxial test is a commonly used technique for
determining cyclic soil strength.
5.3 Cyclic strength depends upon many factors, including
density, confining pressure, applied cyclic shear stress, stress
history, grain structure, age of soil deposit, specimen prepara-
FIG. 1 Schematic Representation of Load-Controlled Cyclic
Triaxial Strength Test Equipment tion procedure, and the frequency, uniformity, and shape of the
D 5311
cyclic wave form. Thus, close attention must be given to
testing details and equipment.
6. Apparatus
6.1 In many ways, triaxial equipment suitable for cyclic
triaxial strength tests is similar to equipment used for the
unconsolidated-undrained triaxial compression test (see Test
Method D 2850) and the consolidated-undrained triaxial com-
pression test (see Test Method D 4767). However, there are
special features described in the following subsections that are
required to perform acceptable cyclic triaxial tests. A schematic
representation of a typical load-controlled cyclic triaxial
strength test set-up is shown in Fig. 1.
6.2 Triaxial Compression Cell—The primary considerations
in selecting the cell are tolerances for the piston, top cap, and
low friction piston seal.
6.2.1 Two linear ball bushings or similar bearings should be
used to guide the load rod to minimize friction and to maintain
alignment.
6.2.2 The load rod diameter should be large enough to
minimize lateral bending. A minimum load rod diameter of ⁄6
the specimen diameter has been used successfully in many
laboratories.
6.2.3 The load rod seal is a critical element in triaxial cell
design for cyclic soils testing. The seal must exert negligible
friction on the load rod. The maximum acceptable piston
friction tolerable without applying load corrections is com-
monly considered to be 6 2 % of the maximum single
amplitude cyclic load applied in the test. The use of an air
bushing as proposed in Ref (3) will meet or exceed these
requirements.
6.2.4 Top and bottom platen alignment is critical if prema-
ture specimen failure caused by the application of a nonuni-
form state of stress to the specimen is to be avoided. Internal
tie-rod triaxial cells that allow for adjustment of alignment
before placement of the chamber have been found to work well
at a number of laboratories. These cells allow the placement of
the cell wall after the specimen is in place between the loading
platens. Acceptable limits of platen eccentricity and parellelism
NOTE 1—(a) Eccentricity and (b) parallelism.
are shown in Fig. 2.
FIG. 2 Limits on Acceptable Platen and Load Rod Alignment
6.2.5 Since in cyclic triaxial tests extension as well as
compression loads may be exerted on the specimen, the load
able to maintain uniform cyclic loadings to at least 20 %
rod shall be connected to the top platen by straight threads
peak-to-peak strains. Unsymmetrical compression-extension
backed by a shoulder on the piston that tightens up against the
load peaks, nonuniformity of pulse duration,“ ringing,” or load
platen.
fall-off at large strains shall not exceed tolerance illustrated in
6.2.6 There shall be provision for specimen drainage at both
Fig. 3. The equipment shall also be able to apply the cyclic load
the top and bottom platens.
about an initial static load on the loading rod. Evaluate
6.2.7 Porous Discs—The specimen shall be separated from
uniformity of the load trace into the failure state to ensure that
the specimen cap and base by rigid porous discs of a diameter
load uniformity criteria presented in previous sections are
equal to that of the specimen. The coefficient of permeability of
achieved. Show this in an appropriate way by calculating the
the discs shall be approximately equal to that of fine sand
−5
percent load drift (P ) between the maximum load (DP )
−4
error max
(3.9 3 10 in./s [1 3 10 cm/s]). The discs shall be regularly
based on the initial loading cycle and the measured load in the
checked to determine whether they have become clogged.
nth cycle as follows:
6.3 Dynamic loading equipment used for load-controlled
D P 5 DP 1D P ! (1)
~
max c e max
cyclic triaxial tests shall be capable of applying a uniform
sinusoidal load at a frequency range of 0.1 to 2.0 Hz. The
@~DP 1DP ! 2 ~DP1DP ! # 3 100
c e max e n
P 5
error
frequency of 1.0 Hz is preferred. The loading device shall be ~DP 1DP !
c e max
D 5311
1 % of the axial load. Generally, the load cell capacity should
be no greater than five times the total maximum load applied to
the test specimen to ensure that the necessary measurement
accuracy is achieved. The minimum performance characteris-
tics of the load cell are presented in Table 1.
6.4.2 Axial Deformation Measurement— Displacement
measuring devices such as linear variable differential trans-
former (LVDT), potentiometer-type deformation transducers,
and eddy current sensors may be used if they have an accuracy
of 6 0.02 % of the initial specimen height (see Table 1).
Accurate deformation measurements require that the trans-
ducer be properly mounted to avoid excessive mechanical
system compression between the load frame, the triaxial cell,
the load cell, an
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