ASTM D7300-06

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Designation: D7300 – 06
Standard Test Method for
Laboratory Determination of Strength Properties of Frozen
Soil at a Constant Rate of Strain
This standard is issued under the fixed designation D7300; 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 (´) 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 2. Referenced Documents
1.1 This test method covers the determination of the 2.1 ASTM Standards:
strength behavior of cylindrical specimens of frozen soil, D653 Terminology Relating to Soil, Rock, and Contained
subjected to uniaxial compression under controlled rates of Fluids
strain. It specifies the apparatus, instrumentation, and proce-
3. Terminology
dures for determining the stress-strain-time, or strength versus
strain rate relationships for frozen soils under deviatoric creep 3.1 Definitions of Terms Specific to This Standard:
3.1.1 creep of frozen ground—the irrecoverable time-
conditions.
1.2 Values stated in SI units are to be regarded as the dependent deviatoric deformation that results from long-term
application of a deviatoric stress.
standard.
3.1.2 excess ice—the volume of ice in the ground which
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the exceeds the total pore volume that the ground would have
under unfrozen conditions.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 3.1.3 failure—the stress condition at failure for a test
specimen. Failure is often taken to correspond to the maximum
bility of regulatory limitations prior to use.
principal stress difference (maximum deviator stress) attained,
or the principal stress difference (deviator stress) at 15 % axial
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
strain, whichever is obtained first during the performance of a
Rock and is the direct responsibility of Subcommittee D18.19 on Frozen Soils and
Rock.
Current edition approved Nov. 1, 2006. Published January 2007. DOI: 10.1520/ For referenced ASTM standards, visit the ASTM website, www.astm.org, or
D7300-06. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
The boldface numbers in parentheses refer to the list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7300 – 06
test. Depending on frozen soil behavior and field application, contain ice in many different forms and sizes, in addition to the
other suitable failure criteria may be defined, such as the pore ice contained in a small laboratory specimen. These large
principal stress difference (deviator stress) at a selected axial ground-ice inclusions (such as ice lenses) will considerably
strain or strain rate. affect the time-dependent behavior of full-scale engineering
3.1.4 ground ice—ageneraltermreferringtoalltypesofice structures.
formed in freezing or frozen ground. 5.3 In order to obtain reliable results, high-quality undis-
3.1.5 ice-bearing permafrost—permafrost that contains ice. turbed representative permafrost samples are required for
3.1.6 ice-bonded permafrost—ice-bearing permafrost in compression strength tests. The quality of the sample depends
which the soil particles are cemented together by ice. onthetypeoffrozensoilsampled,theinsituthermalcondition
3.1.7 ice content—the ratio of the mass of ice contained in at the time of sampling, the sampling method, and the
the pore spaces of frozen soil or rock material, to the mass of transportation and storage procedures prior to testing. The best
solid particles in that material, expressed as percentage. testing program can be ruined by poor-quality samples. In
3.1.8 ice lens—a dominant horizontal, lens-shaped body of addition, one must always keep in mind that the application of
ice of any dimension. laboratory results to practical problems requires much caution
3.1.9 ice-rich permafrost—permafrost containing excess and engineering judgment.
ice.
6. Apparatus
3.1.10 permafrost—soil or rock that remains frozen (tem-
6.1 Axial Loading Device—The axial compression device
perature < 0°C) for a period of two or more years.
shallbecapableofmaintainingaconstantstrainratewithinone
3.1.11 pore ice—iceoccurringintheporesofsoilandrocks.
percent of the applied strain rate. The device may be a screw
3.1.12 sample—piece or quantity of bulk material that has
jack driven by an electric motor through a geared transmission,
been selected by some sampling process.
a platform weighing scale equipped with a screw-jack-
3.1.13 specimen—pieces or quantity taken or prepared from
activated load yoke, a deadweight load apparatus, a hydraulic
a sample for testing.
or pneumatic loading device, or any other compression device
3.1.14 total water content—the ratio of the mass of water
with sufficient capacity and control to provide the loading
(unfrozen water + ice) contained in the pore spaces of frozen
conditions prescribed in Section 8. Vibrations due to the
soil or rock material, to the mass of solid particles in that
operation of the loading device should be kept at a minimum.
material, expressed as percentage.
6.2 Axial Load-Measuring Device—The axial load-
3.1.15 unfrozen water content—the ratio of the mass of
measuring device may be a load ring, electronic load cell,
water (free and adsorbed) contained in the pore spaces of
hydraulicloadcell,oranyotherloadmeasuringdevicecapable
frozen soil or rock material, to the mass of solid particles in
of the accuracy prescribed in this paragraph and may be a part
that material, expressed as percentage (2).
of the axial loading device. For frozen soil with a deviator
3.2 For definitions of other terms used in this test method,
stress at failure of less than 100 kPa, the axial load measuring
refer to Terminology D653.
device shall be capable of measuring the unit axial load to an
4. Summary of Test Method
accuracy equivalent to 1 kPa; for frozen soil with a deviator
stress at failure of 100 kPa and greater, the axial load-
4.1 A cylindrical frozen soil specimen is cut to length and
measuring device shall be capable of measuring the axial load
the ends are machined flat.The specimen is placed in a loading
to an accuracy of 1 % of the axial load at failure.
chamber and allowed to stabilize at a desired test temperature.
6.3 Measurement of Axial Deformation—The interaction
Astrainrateincompressionisappliedtothespecimenandheld
between the test specimen and the testing machine loading
constant at the specified temperature for the duration of the
system can affect the test results. For this reason, in order to
test. Axial stress and deformation of the specimen are moni-
observe the true stress-strain-rate behavior of a frozen soil
tored continuously. Typical results of a set of uniaxial com-
pression tests are shown in Fig. X1.1 (3). specimen, deformations should be measured directly on the
specimen. This can be achieved by mounting deformation
5. Significance and Use
gages on special holders attached to the sides of the specimen
5.1 Understanding the mechanical properties of frozen soils (4). If deformations are measured between the loading platens,
is of primary importance to frozen ground engineering. Data it should be recognized that some initial deformation (seating
from strain rate controlled compression tests are necessary for error) will occur between the specimen ends and the loading
the design of most foundation elements embedded in, or surface of the platens.
bearing on frozen ground. They make it possible to predict the 6.4 Bearing Surfaces—The specimen cap and base shall be
time-dependent settlements of piles and shallow foundations constructed of a noncorrosive impermeable material, and each
under service loads, and to estimate their short and long-term shallhaveacircularplanesurfaceofcontactwiththespecimen
bearing capacity. Such tests also provide quantitative param- and a circular cross section. The weight of the specimen cap
eters for the stability analysis of underground structures that shall be less than 0.5 % of the applied axial load at failure.The
are created for permanent or semi-permanent use. diameter of the cap and base shall be greater than the diameter
5.2 It must be recognized that the structure of frozen soil in of the specimen. The stiffness of the end cap should normally
situ and its behavior under load may differ significantly from be high enough to distribute the applied load uniformly over
that of an artificially prepared specimen in the laboratory. This the loading surface of the specimen. The specimen base shall
is mainly due to the fact that natural permafrost ground may be coupled to the compression chamber so as to prevent lateral
D7300 – 06
motion or tilting, and the specimen cap shall be designed to 7.2 Machining and Preparation of Specimens for Testing
receive the piston, such that the piston-to-cap contact area is (7):
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
trimming or molding the ends of the specimen to parallel planes.The ends
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
(about 3.5 min) or 0.05 mm in 50 mm. Effects of end friction on specimen
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. A temperature 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. At warmer tem-
testing of frozen soils. The lubricated platen should consist of a circular
peratures, surface thawing is a problem, and cutting tools must
sheet of 0.8-mm thick latex membrane, attached to the loading face of a
steelplatenwitha0.5-mmthicklayerofhigh-vacuumsiliconegrease.The be cleaned frequently, for they become coated and clogged
steel platens are polished stainless steel disks about 10 mm larger than the
with frozen soil, reducing their cutting efficiency. Working at
specimen diameter. As the latex sheets and grease layers compress under
colder temperatures is uncomfortable and slow.The soil is also
load, the axial strain of the specimen should be measured using exten-
difficult to work with because of increased hardness; cracks
someters located on the specimen (5, 6).
may also be formed easily in it, due to increased brittleness.
6.5 Thermal Control—The compressive strength of frozen
7.2.3 After being cut roughly to the required dimension,
soil is also affected greatly by temperature and its fluctuations. rectangular specimens are finished usually by one, or a
It is imperative, therefore, that specimens be stored and tested
combination, of the following methods, listed in increasing
in a freezing chamber that has only a small temperature
order of precision:
fluctuation to minimize thermal disturbance. Reduce the effect
(1) Hand shaving with a sharp, straight cutting edge (for
of fluctuations in temperature by enclosing the specimen in an
example a draw knife).
insulating jacket during storage and testing. Reference (7)
(2) A coarse wood rasp or file.
suggests the following permissible temperature variations
(3) Grinding with several grades of emery paper or
when storing and testing frozen soils within the following
grinding stone.
different ranges:
(4) Milling machine equipped with heavy-duty cutters.
Temperature, °C 0 to –2 –2 to –5 –5 to –10 below –10
(5) Drill press (heavy duty) equipped with an end milling
Permissible deviation, °C 60.1 60.2 60.5 61.0
tool.
7.2.3.1 The particular application of each of the methods is
7. Test Specimen
dependent upon the required specimen tolerances.
7.1 Thermal Disturbance Effects:
7.2.3.2 Cylindrical specimens are either machined on a
7.1.1 The strength and deformation properties of frozen soil
working lathe or cut carefully with a coring tube in the
samples are known to be affected by sublimation, evaporation,
laboratory. They can also be cored from block samples, using
andthermaldisturbance.Theireffectisintheredistributionand
a diamond set core barrel and a large industrial drill press. For
ultimate loss of moisture from the sample as the result of a
machining on a working lathe, the best results are obtained
temperature
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