ASTM D5520-94
(Test Method)Standard Test Method for Laboratory Determination of Creep Properties of Frozen Soil Samples by Uniaxial Compression
Standard Test Method for Laboratory Determination of Creep Properties of Frozen Soil Samples by Uniaxial Compression
SCOPE
1.1 This test method covers the determination of the creep behavior of cylindrical specimens of frozen soil, subjected to uniaxial compression. It specifies the apparatus, instrumentation, and procedures for determining the stress-strain-time, or strength versus strain rate relationships for frozen soils under deviatoric creep conditions.
1.2 Although this test method is one that is most commonly used, it is recognized that creep properties of frozen soil related to certain specific applications, can also be obtained by some alternative procedures, such as stress-relaxation tests, simple shear tests, and beam flexure tests. Creep testing under triaxial test conditions will be covered in another standard.
1.3 Values stated in SI units are to be regarded as the standard.
1.4 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: D 5520 – 94
AMERICAN SOCIETY FOR TESTING AND MATERIALS
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Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Laboratory Determination of Creep Properties of Frozen Soil
Samples by Uniaxial Compression
This standard is issued under the fixed designation D 5520; 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.
INTRODUCTION
Knowledge of the stress-strain-strength behavior of frozen soil is of great importance for civil
engineering construction in permafrost regions. The behavior of frozen soils under load is usually very
different from that of unfrozen soils because of the presence of ice and unfrozen water films. In
particular, frozen soils are much more subject to creep and relaxation effects, and their behavior is
strongly affected by temperature change. In addition to creep, volumetric consolidation may also
develop in frozen soils having large unfrozen water or gas contents.
As with unfrozen soil, the deformation and strength behavior of frozen soils depends on interparticle
friction, particle interlocking, and cohesion. In frozen soil, however, bonding of particles by ice may
be the dominant strength factor. The strength of ice in frozen soil is dependent on many factors, such
as temperature, pressure, strain rate, grain size, crystal orientation, and density. At very high ice
contents (ice-rich soils), frozen soil behavior under load is similar to that of ice. In fact, for
fine-grained soils, experimental data suggest that the ice matrix dominates when mineral volume
fraction is less than about 50 %. At low ice contents, however, (ice-poor soils), when interparticle
forces begin to contribute to strength, the unfrozen water films play an important role, especially in
fine-grained soils. Finally, for frozen sand, maximum strength is attained at full ice saturation and
maximum dry density (1).
1. Scope bility of regulatory limitations prior to use.
1.1 This test method covers the determination of the creep
2. Referenced Documents
behavior of cylindrical specimens of frozen soil, subjected to
2.1 ASTM Standards:
uniaxial compression. It specifies the apparatus, instrumenta-
D 653 Terminology Relating to Soil, Rock and Contained
tion, and procedures for determining the stress-strain-time, or
Fluids
strength versus strain rate relationships for frozen soils under
D 2850 Test Method for Unconsolidated Undrained
deviatoric creep conditions.
Strength of Cohesive Soils in Triaxial Compression
1.2 Although this test method is one that is most commonly
D 4083 Practice for Description of Frozen Soils (Visual
used, it is recognized that creep properties of frozen soil related
Manual Procedure)
to certain specific applications, can also be obtained by some
D 4341 Test Method for Creep of Cylindrical Hard Rock
alternative procedures, such as stress-relaxation tests, simple
Core Specimens in Uniaxial Compression
shear tests, and beam flexure tests. Creep testing under triaxial
D 4405 Test Method for Creep of Cylindrical Soft Rock
test conditions will be covered in another standard.
Core Specimens in Uniaxial Compression
1.3 Values stated in SI units are to be regarded as the
D 4406 Test Method for Creep of Cylindrical Rock Core
standard.
Specimens in Triaxial Compression
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
3.1 Definitions:
priate safety and health practices and determine the applica-
3.1.1 creep—of frozen ground, the irrecoverable time-
dependent deviatoric deformation that results from long-term
This test method is under the jurisdiction of ASTM Committee D-18 on Soil
application of a deviatoric stress.
and Rock and is the direct responsibility of Subcommittee D18.19 on Frozen Soils
3.1.2 excess ice—the volume of ice in the ground which
and Rock.
Current edition approved March 15, 1994. Published May 1994.
The boldface numbers in parentheses refer to the list of references at the end of
the text. Annual Book of ASTM Standards, Vol 04.08.
D 5520
exceeds the total pore volume that the ground would have affect the time-dependent behavior of full-scale engineering
under unfrozen conditions. structures.
3.1.3 ground ice—a general term referring to all types of ice 5.3 In order to obtain reliable results, high-quality undis-
formed in freezing or frozen ground. turbed representative permafrost samples are required for creep
3.1.4 ice-bearing permafrost—permafrost that contains ice. tests. The quality of the sample depends on the type of frozen
3.1.5 ice-bonded permafrost—ice-bearing permafrost in soil sampled, the in situ thermal condition at the time of
which the soil particles are cemented together by ice. sampling, the sampling method, and the transportation and
3.1.6 ice content—the ratio of the mass of ice contained in storage procedures prior to testing. The best testing program
the pore spaces of frozen soil or rock material, to the mass of can be ruined by poor-quality samples. In addition, one must
solid particles in that material, expressed as percentage. always keep in mind that the application of laboratory results
3.1.7 ice lens—a dominant horizontal, lens-shaped body of to practical problems requires much caution and engineering
ice of any dimension. judgment.
3.1.8 ice-rich permafrost—permafrost containing excess
6. Apparatus
ice.
6.1 Axial Loading Device—The axial compression device
3.1.9 permafrost—perennially frozen soil or rock.
shall be capable of maintaining a constant load or stress within
3.1.10 pore ice—ice occurring in the pores of soil and rocks.
one percent of the applied load or stress. The device may be a
3.1.11 sample—a portion of a material intended to be
screw jack driven by an electric motor through a geared
representative of the whole.
transmission, a platform weighing scale equipped with a
3.1.12 specimen—a piece or portion of a sample used to
screw-jack-activated load yoke, a deadweight load apparatus, a
make a test.
hydraulic or pneumatic loading device, or any other compres-
3.1.13 total water content—the ratio of the mass of water
sion device with sufficient capacity and control to provide the
(unfrozen water + ice) contained in the pore spaces of frozen
loading conditions prescribed in Section 8. Vibrations due to
soil or rock material, to the mass of solid particles in that
the operation of the loading device should be kept at a
material, expressed as percentage.
minimum.
3.1.14 unfrozen water content—the ratio of the mass of
6.2 Axial Load-Measuring Device—The axial load-
water (free and adsorbed) contained in the pore spaces of
measuring device may be a load ring, electronic load cell,
frozen soil or rock material, to the mass of solid particles in
hydraulic load cell, or any other load measuring device capable
that material, expressed as percentage (2).
of the accuracy prescribed in this paragraph and may be a part
3.2 For definitions of other terms used in this test method,
of the axial loading device. For frozen soil with a deviator
refer to Terminology D 653.
stress at failure of less than 100 kPa, the axial loadmeasuring
4. Summary of Test Method
device shall be capable of measuring the unit axial load to an
accuracy equivalent to 1 kPa; for frozen soil with a deviator
4.1 A cylindrical frozen soil specimen is cut to length and
stress at failure of 100 kPa and greater, the axial load-
the ends are machined flat. The specimen is placed in a loading
measuring device shall be capable of measuring the axial load
chamber and allowed to stabilize at a desired test temperature.
to an accuracy of 1 % of the axial load at failure.
An axial compression stress is applied to the specimen and held
6.3 Measurement of Axial Deformation—The interaction
constant at the specified temperature for the duration of the
between the test specimen and the testing machine loading
test. Specimen deformation is monitored continuously. Typical
system can affect the creep test results. For this reason, in order
results of a uniaxial compression creep test are shown in Fig.
to observe the true strain-time behavior of a frozen soil
X1.1.
specimens, deformations should be measured directly on the
5. Significance and Use
specimen. This can be achieved by mounting deformation
5.1 Understanding the mechanical properties of frozen soils gages on special holders attached to the sides of the specimen
is of primary importance to permafrost engineering. Data from (3). If deformations are measured between the loading platens,
creep tests are necessary for the design of most foundation it should be recognized that some initial deformation (seating
elements embedded in, or bearing on frozen ground. They error) will occur between the specimen ends and the loading
make it possible to predict the time-dependent settlements of surface of the platens.
piles and shallow foundations under service loads, and to 6.4 Bearing Surfaces—The specimen cap and base shall be
estimate their short- and long-term bearing capacity. Creep constructed of a noncorrosive impermeable material, and each
tests also provide quantitative parameters for the stability shall have a circular plane surface of contact with the specimen
analysis of underground structures that are created for perma- and a circular cross section. The weight of the specimen cap
nent use. shall be less than 0.5 % of the applied axial load at failure. The
5.2 It must be recognized that the structure of frozen soil in diameter of the cap and base shall be greater than the diameter
situ and its behavior under load may differ significantly from of the specimen. The stiffness of the end cap should normally
that of an artificially prepared specimen in the laboratory. This be high enough to distribute the applied load uniformly over
is mainly due to the fact that natural permafrost ground may the loading surface of the specimen. The specimen base shall
contain ice in many different forms and sizes, in addition to the be coupled to the compression chamber so as to prevent lateral
pore ice contained in a small laboratory specimen. These large motion or tilting, and the specimen cap shall be designed to
ground-ice inclusions (such as ice lenses) will considerably receive the piston, such that the piston-to-cap contact area is
D 5520
concentric with the cap. required, the type of soil, and the particular test being per-
formed. Follow similar procedures for cutting and machining
NOTE 1—It is advisable not to use ball or spherical seats that would
both naturally frozen and artificially frozen samples.
allow rotation of the platens, but rather special care should be taken in
7.2.2 Handle frozen soil samples with gloves and all tools
trimming or molding the ends of the specimen to parallel planes. The ends
of the specimen shall be flat to 0.02 mm and shall not depart from and equipment kept in the cold room to avoid sample damage
perpendicularity to the axis of the specimen by more than 0.001 radian
by localized thawing. A temperature of − 5 6 1°C is the most
(about 3.5 min) or 0.05 mm in 50 mm. Effects of end friction on specimen
suitable ambient temperature for machining with respect to
deformation can be tolerated if the height to diameter ratio of the test
material workability and personal comfort.
specimen is two to three. However, it is recommended that lubricated
7.2.3 Cylindrical specimens are either machined on a work-
platens be used whenever possible in the uniaxial compression and creep
ing lathe or cut carefully with a coring tube in the laboratory.
testing of frozen soils. The lubricated platen should consist of a circular
sheet of 0.8-mm thick latex membrane, attached to the loading face of a They can also be cored from block samples, using a diamond
steel platen with a 0.5-mm thick layer of highvacuum silicone grease. The
set core barrel and a large industrial drill press. For machining
steel platens are polished stainless steel disks about 10 mm larger than the
on a working lathe, the best results are obtained when the
specimen diameter. As the latex sheets and grease layers compress under
specimen is turned at 690 r/min and the carriage feed set at 30
load, the axial strain of the specimen should be measured using exten-
mm per 36 revolutions. Limit the maximum depth of cut to
someters located on the specimen (4, 5).
0.38 mm. A tungsten carbide cutting tool, with a minimum
6.5 Thermal Control—The compressive strength of frozen
back clearance of 45°, gives the best results. For clean cuts,
soil is also affected greatly by temperature and its fluctuations.
sharpen the tool often, as the abrasive action of the soil dulls
It is imperative, therefore, that specimens be stored and tested
the edge quickly (7). Shaping coarse sand or gravel specimens
in a freezing chamber that has only a small temperature
on a lathe is difficult, because the soil grains are pulled out
fluctuation to minimize thermal disturbance. Reduce the effect
leaving an uneven pitted surface, that should be made smooth
of fluctuations in temperature by enclosing the specimen in an
by filling the pits with ice and fine sand mixture. It is important
insulating jacket during storage and testing. Reference (6)
that the ends of the specimen are parallel and plane, so that
suggests the following permissible temperature variations
intimate contact occurs with the loading platens.
when storing and testing frozen soils within the following
7.3 Test Specimen Shape and Size:
different ranges:
7.3.1 Both the shape and size of frozen soil test specimens
Temperature,° C 0 to − 2 −2 to − 5 −5 to − 10 below − 10
can influence the results of uniaxial compression tests. The
Permissible devia- 60.1 60.2 60.5 61.0
sizes of specimens used in compression testing are generally a
tion,° C
compromise between theoretical and practical considerations.
7. Test Specimen
Some of these considerations are:
7.1 Thermal Disturbance Effects:
7.3.1.1 The influence of boundary conditions of the test,
7.1.1 The strength and deformation properties of frozen soil
that, among other things, include the lateral restraint imposed
samples are known to be affected by sublimation, evaporation,
on the test specimen by the end platens,
and thermal disturbance. Their effect is in the redistribution and
7.3.1.2 The maximum size of particles in a soil specimen,
ultimate loss of moist
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