ASTM D5520-18

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Designation: D5520 − 11 D5520 − 18
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. 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
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 In ice-rich soils (that is, soils where the ratio of the mass
of ice contained in the pore spaces of frozen soil or rock material, to the mass of solid particles in that
material is high), 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*
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.4.1 For the purposes of comparing, a measured or calculated value(s) with specified limits, the measured or calculated value(s)
shall be rounded to the nearest decimal or significant digits in the specified limits.
1.4.2 The procedures used to specify how data are collected/recorded or calculated in this standard are regarded as the industry
standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not
consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives;
This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.19 on Frozen Soils and Rock.
Current edition approved Nov. 1, 2011Nov. 15, 2018. Published January 2012December 2018. Originally approved in 1994. Last previous edition approved in 20062011
ε1
as D5520–94(2006)D5520 .–11. DOI: 10.1520/D5520-11. 10.1520/D5520-18.
The boldface numbers in parentheses refer to the list of references at the end of the text.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5520 − 18
and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations.
It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.
1.5 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D2850 Test Method for Unconsolidated-Undrained Triaxial Compression Test on Cohesive Soils
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4083 Practice for Description of Frozen Soils (Visual-Manual Procedure)
D4341 Test Method for Creep of Hard Rock Core Specimens in Uniaxial Compression at Ambient or Elevated Temperature
(Withdrawn 2005)
D4405 Test Method for Creep of Soft Rock Core Specimens in Uniaxial Compression at Ambient or Elevated Temperature
(Withdrawn 2005)
D4406 Test Method for Creep of Rock Core Specimens in Triaxial Compression at Ambient or Elevated Temperatures
(Withdrawn 2005)
D6026 Practice for Using Significant Digits in Geotechnical Data
3. Terminology
3.1 Definitions:
3.1.1 For definitions of common technical terms in this standard, refer to Terminology D653.
3.1.2 Definitions of the components of freezing and thawing soils shall be in accordance with the terminology in Practice
D4083.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 The following terms supplement those in Practice D4083 and in the glossary on permafrost terms by Harris et al (2).
3.2.2 creep—creep, n—of frozen ground, the irrecoverable time-dependent deviatoric deformation that results from long-term
application of a deviatoric stress.
3.2.3 excess ice—the volume of ice in the ground which exceeds the total pore volume that the ground would have under
unfrozen conditions.
3.2.4 ground ice—a general term referring to all types of ice formed in freezing or frozen ground.
3.2.5 ice-bearing permafrost—permafrost that contains ice.
3.2.6 ice-bonded permafrost—ice-bearing permafrost in which the soil particles are cemented together by ice.
3.2.7 ice content—the ratio of the mass of ice contained in the pore spaces of frozen soil or rock material, to the mass of solid
particles in that material, expressed as percentage.
3.2.8 ice lens—a dominant horizontal, lens-shaped body of ice of any dimension.
3.2.3 ice-rich permafrost—permafrost, n—permafrost containing excess ice.
3.2.10 permafrost—perennially frozen soil or rock.
3.2.4 pore ice—ice, n—ice occurring in the pores of soil and rocks.
3.2.12 sample—a portion of a material intended to be representative of the whole.
3.2.13 specimen—a piece or portion of a sample used to make a test.
3.2.5 total water content—content, n—the ratio of the mass of water (unfrozen water + ice) contained in the pore spaces of
frozen soil or rock material, to the mass of solid particles in that material, expressed as percentage.
3.2.6 unfrozen water content—content, n—the ratio of the mass of water (free and adsorbed) contained in the pore spaces of
frozen soil or rock material, to the mass of solid particles in that material, expressed as percentage (3).
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
D5520 − 18
4. Summary of Test Method
4.1 A cylindrical frozen soil specimen is cut to length and the ends are machined flat. The specimen is placed in a loading
chamber and allowed to stabilize at a desired test temperature. An axial compression stress is applied to the specimen and held
constant at the specified temperature for the duration of the test. Specimen deformation is monitored continuously. Typical results
of a uniaxial compression creep test are shown in Fig. X1.1.
5. Significance and Use
5.1 Understanding the mechanical properties of frozen soils is of primary importance to permafrost engineering. Data from
creep tests are necessary for the design of most foundation elements embedded in, or bearing on frozen ground. They make it
possible to predict the time-dependent settlements of piles and shallow foundations under service loads, and to estimate their short-
and long-term bearing capacity. Creep tests also provide quantitative parameters for the stability analysis of underground structures
that are created for permanent use.
5.2 It must be recognized that the structure of frozen soil in situ and its behavior under load may differ significantly from that
of an artificially prepared specimen in the laboratory. This is mainly due to the fact that natural permafrost ground may contain
ice in many different forms and sizes, in addition to the pore ice contained in a small laboratory specimen. These large ground-ice
inclusions (such as ice lenses) lenses, a dominant horizontal, lens-shaped body of ice of any dimension) will considerably affect
the time-dependent behavior of full-scale engineering structures.
5.3 In order to obtain reliable results, high-quality intact representative permafrost samples are required for creep tests. The
quality of the sample depends on the type of frozen soil sampled, the in situ thermal condition at the time of sampling, the sampling
method, and the transportation and storage procedures prior to testing. The best testing program can be ruined by poor-quality
samples. In addition, one must always keep in mind that the application of laboratory results to practical problems requires much
caution and engineering judgment.
NOTE 1—The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the
equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective
testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable
results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
6. Apparatus
6.1 Axial Loading Device—The axial compression device shall be capable of maintaining a constant load or stress within one
percent of the applied load or stress. The device may be a screw jack driven by an electric motor through a geared transmission,
a platform weighing scale equipped with a screw-jack-activated load yoke, a deadweight load apparatus, a hydraulic or pneumatic
loading device, or any other compression device with sufficient capacity and control to provide the loading conditions prescribed
in Section 8. Vibrations due to the operation of the loading device should be kept at a minimum.
6.2 Axial Load-Measuring Device—The axial load-measuring device may be a load ring, electronic load cell, hydraulic load
cell, or any other load measuring device capable of the accuracy prescribed in this paragraph and may be a part of the axial loading
device. For frozen soil with a deviator stress at failure of less than 100 kPa, the axial load measuring device shall be capable of
measuring the unit axial load to an accuracy equivalent to 1 kPa; for frozen soil with a deviator stress at failure of 100 kPa and
greater, the axial load measuring device shall be capable of measuring the axial load to an accuracy of 1 % of the axial load at
failure.
6.3 Measurement of Axial Deformation—The interaction between the test specimen and the testing machine loading system can
affect the creep test results. For this reason, in order to observe the true strain-time behavior of a frozen soil specimens,
deformations should be measured directly on the specimen. This can be achieved by mounting deformation gages on special
holders attached to the sides of the specimen (4). If deformations are measured between the loading platens, it should be recognized
that some initial deformation (seating error) will occur between the specimen ends and the loading surface of the platens.
6.4 Bearing Surfaces—The specimen cap and base shall be constructed of a noncorrosive impermeable material, and each shall
have a circular plane surface of contact with the specimen and a circular cross section. The weight of the specimen cap shall be
less than 0.5 % of the applied axial load at failure. The diameter of the cap and base shall be greater than the diameter of the
specimen. The stiffness of the end cap should normally be high enough to distribute the applied load uniformly over the loading
surface of the specimen. The specimen base shall be coupled to the compression chamber so as to prevent lateral motion or tilting,
and the specimen cap shall be designed to receive the piston, such that the piston-to-cap contact area is concentric with the cap.
NOTE 2—It is advisable not to use ball or spherical seats that would allow rotation of the platens, but rather special care should be taken in 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 perpendicularity to
the axis of the specimen by more than 0.001 radian (about 3.5 min) or 0.05 mm in 50 mm. Effects of end friction on specimen deformation can be tolerated
if the height to diameter ratio of the test specimen is two to three. However, it is recommended that lubricated platens be used whenever possible in the
uniaxial compression and creep 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 steel platen with a 0.5-mm thick layer of high vacuum silicone grease. The steel platens are polished stainless steel disks about
10 mm larger than the specimen diameter. As the latex sheets and grease layers compress under load, the axial strain of the specimen should be measured
using extensometers located on the specimen (5, 6).
D5520 − 18
6.5 Thermal Control—The compressive strength of frozen soil is also affected greatly by temperature and its fluctuations. It is
imperative, therefore, that specimens be stored and tested in a freezing chamber that has only a small temperature fluctuation to
minimize thermal disturbance. Reduce the effect of fluctuations in temperature by enclosing the specimen in an insulating jacket
during storage and testing. Reference (7) suggests the following permissible temperature variations when storing and testing frozen
soils within the following different ranges:
Temperature,° C 0 to − 2 −2 to − 5 −5 to − 10 below − 10
Permissible ±0.1 ±0.2 ±0.5 ±1.0
deviation,° C
7. Test Specimen
7.1 Thermal Disturbance Effects:
7.1.1 The strength and deformation properties of frozen soil samples are known to be affected by sublimation, evaporation, and
thermal disturbance. Their effect is in the redistribution and ultimate loss of moisture from the sample as the result of a temperature
gradient or low-humidity environment, or both. Loss of moisture reduces the cohesion between soil particles and may reduce the
strength (that is dependent on temperature). The effects of moisture redistribution in frozen soil are thought to change its strength
and creep behavior.
7.1.2 Thermal disturbance of a frozen sample refers not only to thawing, but also to temperature fluctuations. Soil structure may
be changed completely if the sample is thawed and then refrozen. Temperature fluctuations can set up thermal gradients, causing
moisture redistribution and possible change in the unfrozen moisture content. Take care, therefore, to ensure that frozen soil
specimens remain in their natural state, and that they are protected against the detrimental effects of sublimation and thermal
disturbance until testing is completed.
7.1.3 In the event that the soil sample is not maintained at the in situ temperature prior to testing, bring the test specimen to
the test temperature from a higher temperature to reduce the hysteresis effect on the unfrozen water content.
7.1.4 Before testing, maintain the test specimen at the test temperature for a sufficient period, to ensure that the temperature is
uniform throughout the volume.
7.2 Machining and Preparation of Specimens for Testing:
7.2.1 The machining and preparation procedures used for frozen soils depend upon the size and shape of the specimen required,
the type of soil, and the particular test being performed. Follow similar procedures for cutting and machining both naturally frozen
and artificially frozen samples.
7.2.2 Handle frozen soil samples with gloves and all tools and equipment kept in the cold room to avoid sample damage by
localized thawing. A temperature of − 5 6 1°C is the most suitable ambient temperature for machining with respect to material
workability and personal comfort.
7.2.3 Cylindrical specimens are either machined on a working lathe or cut carefully with a coring tube in the laboratory. They
can also be cored from block samples, using a diamond set core barrel and a large industrial drill press. For machining on a working
lathe, the best results are obtained when the specimen is turned at 690 r/min and the carriage feed set at 30 mm per 36 revolutions.
Limit the maximum depth of cut to 0.38 mm. A tungsten carbide cutting tool, with a minimum back clearance of 45°, gives the
best results. For clean cuts, sharpen the tool often, as the abrasive action of the soil dulls the edge quickly (8). Shaping coarse sand
or gravel specimens on a lathe is difficult, because the soil grains are pulled out leaving an uneven pitted surface that should be
made smooth by filling the pits with ice and fine sand mixture. It is important that the ends of the specimen are parallel and plane,
so that intimate contact occurs with the loading platens.
7.3 Test Specimen Shape and Size:
7.3.1 Both the shape and size of frozen soil test specimens can influence the results of uniaxial compression tests. The sizes of
specimens used in compression testing are generally a compromise between theoretical and practical considerations. Some of these
considerations are:
7.3.1.1 The influence of boundary conditions of the test, that, among other things, include the lateral restraint imposed on the
test specimen by the end platens,
7.3.1.2 The maximum size of particles in a soil specimen,
7.3.1.3 The loading capacity of the available loading equipment,
7.3.1.4 The maximum dimensions and weight of a test specimen that can be handled conveniently,
7.3.1.5 The size of soil samples that can be taken from a field site using common sampling methods, and
7.3.1.6 Equipment that is readily available to shape and protect specimens.
7.3.2 To reduce the influence of boundary conditions and that of maximum soil particle size, the test specimen should be as large
as can be tested conveniently.
7.3.3 From the testing of unfrozen soils, the importance of the ratio of specimen height to diameter has long been recognized
as an important factor where the type of loading platens influences the test results. Experience with compression testing of frozen
soils (7, 9, 10) indicates that consistent creep and strength results can be obtained when the height to diameter ratio is 2 to 3,
between 3:1 and 2:1, regardless of the type of end platens used in testing. Based on this information, it is recommended that: the
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