ASTM D5520-94(2001)
(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:D5520–94 (Reapproved 2001)
Standard Test Method for
Laboratory Determination of Creep Properties of Frozen Soil
Samples by Uniaxial Compression
This standard is issued under the fixed designation D5520; 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 (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
engineeringconstructioninpermafrostregions.Thebehavioroffrozensoilsunderloadisusuallyvery
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.
Aswithunfrozensoil,thedeformationandstrengthbehavioroffrozensoilsdependsoninterparticle
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 responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
1.1 This test method covers the determination of the creep
bility of regulatory limitations prior to use.
behavior of cylindrical specimens of frozen soil, subjected to
uniaxial compression. It specifies the apparatus, instrumenta-
2. Referenced Documents
tion, and procedures for determining the stress-strain-time, or
2.1 ASTM Standards:
strength versus strain rate relationships for frozen soils under
D653 Terminology Relating to Soil, Rock, and Contained
deviatoric creep conditions.
Fluids
1.2 Although this test method is one that is most commonly
D2850 Test Method for Unconsolidated— Undrained Tri-
used,itisrecognizedthatcreeppropertiesoffrozensoilrelated
axial Compression Test on Cohesive Soils
to certain specific applications, can also be obtained by some
D4083 Practice for Description of Frozen Soils (Visual-
alternative procedures, such as stress-relaxation tests, simple
Manual Procedure)
shear tests, and beam flexure tests. Creep testing under triaxial
D4341 Test Method for Creep of Cylindrical Hard 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
D4405 Test Method for Creep of Cylindrical Soft Rock
standard.
Core Specimens in Uniaxial Compression
1.4 This standard does not purport to address all of the
D4406 Test Method for Creep of Cylindrical Rock Core
safety concerns, if any, associated with its use. It is the
Specimens in Triaxial Compression
3. Terminology
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.19 on Frozen Soils and
3.1 Definitions:
Rock.
Current edition approved March 15, 1994. Published May 1994.
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
the text. Annual Book of ASTM Standards, Vol 04.08.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5520
3.1.1 creep—of frozen ground, the irrecoverable time- is mainly due to the fact that natural permafrost ground may
dependent deviatoric deformation that results from long-term containiceinmanydifferentformsandsizes,inadditiontothe
application of a deviatoric stress. pore ice contained in a small laboratory specimen.These large
3.1.2 excess ice—the volume of ice in the ground which ground-ice inclusions (such as ice lenses) will considerably
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—ageneraltermreferringtoalltypesofice 5.3 In order to obtain reliable results, high-quality undis-
formed in freezing or frozen ground. turbedrepresentativepermafrostsamplesarerequiredforcreep
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.
shallbecapableofmaintainingaconstantloadorstresswithin
3.1.10 poreice—iceoccurringintheporesofsoilandrocks.
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-activatedloadyoke,adeadweightloadapparatus,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
hydraulicloadcell,oranyotherloadmeasuringdevicecapable
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 D653.
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-
theendsaremachinedflat.Thespecimenisplacedinaloading
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.
Anaxialcompressionstressisappliedtothespecimenandheld
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
results of a uniaxial compression creep test are shown in Fig. systemcanaffectthecreeptestresults.Forthisreason,inorder
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 shallhaveacircularplanesurfaceofcontactwiththespecimen
analysis of underground structures that are created for perma- and a circular cross section. The weight of the specimen cap
nent use. shallbelessthan0.5%oftheappliedaxialloadatfailure.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
D5520
the loading surface of the specimen. The specimen base shall 7.1.4 Before testing, maintain the test specimen at the test
be coupled to the compression chamber so as to prevent lateral temperature for a sufficient period, to ensure that the tempera-
motion or tilting, and the specimen cap shall be designed to ture is uniform throughout the volume.
receive the piston, such that the piston-to-cap contact area is 7.2 Machining and Preparation of Specimens for Testing:
concentric with the cap.
7.2.1 The machining and preparation procedures used for
frozen soils depend upon the size and shape of the specimen
NOTE 1—It is advisable not to use ball or spherical seats that would
required, the type of soil, and the particular test being per-
allow rotation of the platens, but rather special care should be taken in
formed. Follow similar procedures for cutting and machining
trimmingormoldingtheendsofthespecimentoparallelplanes.Theends
both naturally frozen and artificially frozen samples.
of the specimen shall be flat to 0.02 mm and shall not depart from
perpendicularity to the axis of the specimen by more than 0.001 radian
7.2.2 Handle frozen soil samples with gloves and all tools
(about3.5min)or0.05mmin50mm.Effectsofendfrictiononspecimen
and equipment kept in the cold room to avoid sample damage
deformation can be tolerated if the height to diameter ratio of the test
by localized thawing.Atemperature of−5 6 1°C is the most
specimen is two to three. However, it is recommended that lubricated
suitable ambient temperature for machining with respect to
platens be used whenever possible in the uniaxial compression and creep
material workability and personal comfort.
testing of frozen soils. The lubricated platen should consist of a circular
7.2.3 Cylindrical specimens are either machined on a work-
sheet of 0.8-mm thick latex membrane, attached to the loading face of a
ing lathe or cut carefully with a coring tube in the laboratory.
steelplatenwitha0.5-mmthicklayerofhighvacuumsiliconegrease.The
steelplatensarepolishedstainlesssteeldisksabout10mmlargerthanthe
They can also be cored from block samples, using a diamond
specimen diameter.As the latex sheets and grease layers compress under
set core barrel and a large industrial drill press. For machining
load, the axial strain of the specimen should be measured using exten-
on a working lathe, the best results are obtained when the
someters located on the specimen (4, 5).
specimen is turned at 690 r/min and the carriage feed set at 30
6.5 Thermal Control—The compressive strength of frozen mm per 36 revolutions. Limit the maximum depth of cut to
0.38 mm. A tungsten carbide cutting tool, with a minimum
soil is also affected greatly by temperature and its fluctuations.
back clearance of 45°, gives the best results. For clean cuts,
It is imperative, therefore, that specimens be stored and tested
sharpen the tool often, as the abrasive action of the soil dulls
in a freezing chamber that has only a small temperature
the edge quickly (7). Shaping coarse sand or gravel specimens
fluctuation to minimize thermal disturbance. Reduce the effect
on a lathe is difficult, because the soil grains are pulled out
of fluctuations in temperature by enclosing the specimen in an
leaving an uneven pitted surface, that should be made smooth
insulating jacket during storage and testing. Reference (6)
byfillingthepitswithiceandfinesandmixture.Itisimportant
suggests the following permissible temperature variations
that the ends of the specimen are parallel and plane, so that
when storing and testing frozen soils within the following
intimate contact occurs with the loading platens.
different ranges:
7.3 Test Specimen Shape and Size:
Temperature,° C 0 to − 2 −2 to − 5 −5 to − 10 below − 10
Permissible devia- 60.1 60.2 60.5 61.0
7.3.1 Both the shape and size of frozen soil test specimens
tion,° C
can influence the results of uniaxial compression tests. The
sizes of specimens used in compression testing are generally a
7. Test Specimen
compromise between theoretical and practical considerations.
7.1 Thermal Disturbance Effects:
Some of these considerations are:
7.3.1.1 The influence of boundary conditions of the test,
7.1.1 Thestrengthanddeformationpropertiesoffrozensoil
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,
andthermaldisturbance.Theireffectisintheredistributionand
7.3.1.2 The maximum size of particles in a soil specimen,
u
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