1、Designation: D 5520 94 (Reapproved 2006)e1Standard Test Method forLaboratory Determination of Creep Properties of Frozen SoilSamples by Uniaxial Compression1This standard is issued under the fixed designation D 5520; the number immediately following the designation indicates the year oforiginal adop
2、tion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEditorial changes were made in June 2006.INTRODUCTIONKnowledge of the stress-
3、strain-strength behavior of frozen soil is of great importance for civilengineering construction in permafrost regions. The behavior of frozen soils under load is usually verydifferent from that of unfrozen soils because of the presence of ice and unfrozen water films. Inparticular, frozen soils are
4、 much more subject to creep and relaxation effects, and their behavior isstrongly affected by temperature change. In addition to creep, volumetric consolidation may alsodevelop in frozen soils having large unfrozen water or gas contents.As with unfrozen soil, the deformation and strength behavior of
5、 frozen soils depends on interparticlefriction, particle interlocking, and cohesion. In frozen soil, however, bonding of particles by ice maybe the dominant strength factor. The strength of ice in frozen soil is dependent on many factors, suchas temperature, pressure, strain rate, grain size, crysta
6、l orientation, and density. At very high icecontents (ice-rich soils), frozen soil behavior under load is similar to that of ice. In fact, forfine-grained soils, experimental data suggest that the ice matrix dominates when mineral volumefraction is less than about 50 %. At low ice contents, however,
7、 (ice-poor soils), when interparticleforces begin to contribute to strength, the unfrozen water films play an important role, especially infine-grained soils. Finally, for frozen sand, maximum strength is attained at full ice saturation andmaximum dry density (1).21. Scope1.1 This test method covers
8、 the determination of the creepbehavior of cylindrical specimens of frozen soil, subjected touniaxial compression. It specifies the apparatus, instrumenta-tion, and procedures for determining the stress-strain-time, orstrength versus strain rate relationships for frozen soils underdeviatoric creep c
9、onditions.1.2 Although this test method is one that is most commonlyused, it is recognized that creep properties of frozen soil relatedto certain specific applications, can also be obtained by somealternative procedures, such as stress-relaxation tests, simpleshear tests, and beam flexure tests. Cre
10、ep testing under triaxialtest conditions will be covered in another standard.1.3 Values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard
11、to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 2850 Test Method for Unconsolidated-Undrained Tri-axial Compression
12、Test on Cohesive SoilsD 4083 Practice for Description of Frozen Soils (Visual-Manual Procedure)D 4341 Test Method for Creep of Hard Rock Core Speci-mens in Uniaxial Compression at Ambient or ElevatedTemperature41This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is t
13、he direct responsibility of Subcommittee D18.19 on Frozen Soils andRock.Current edition approved May 1, 2006. Published June 2006. Originallyapproved in 1994. Last previous edition approved in 2001 as D 552094(2001).2The boldface numbers in parentheses refer to the list of references at the end ofth
14、e text.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn.1Copyright ASTM International, 100 Barr Har
15、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D 4405 Test Method for Creep of Soft Rock Core Speci-mens in Uniaxial Compression at Ambient or ElevatedTemperature4D 4406 Test Method for Creep of Rock Core Specimens inTriaxial Compression at Ambient or Elevated Tempera-tures4
16、3. Terminology3.1 Definitions:3.1.1 creepof frozen ground, the irrecoverable time-dependent deviatoric deformation that results from long-termapplication of a deviatoric stress.3.1.2 excess icethe volume of ice in the ground whichexceeds the total pore volume that the ground would haveunder unfrozen
17、 conditions.3.1.3 ground icea general term referring to all types of iceformed in freezing or frozen ground.3.1.4 ice-bearing permafrostpermafrost that contains ice.3.1.5 ice-bonded permafrostice-bearing permafrost inwhich the soil particles are cemented together by ice.3.1.6 ice contentthe ratio of
18、 the mass of ice contained inthe pore spaces of frozen soil or rock material, to the mass ofsolid particles in that material, expressed as percentage.3.1.7 ice lensa dominant horizontal, lens-shaped body ofice of any dimension.3.1.8 ice-rich permafrostpermafrost containing excessice.3.1.9 permafrost
19、perennially frozen soil or rock.3.1.10 pore iceice occurring in the pores of soil and rocks.3.1.11 samplea portion of a material intended to berepresentative of the whole.3.1.12 specimena piece or portion of a sample used tomake a test.3.1.13 total water contentthe ratio of the mass of water(unfroze
20、n water + ice) contained in the pore spaces of frozensoil or rock material, to the mass of solid particles in thatmaterial, expressed as percentage.3.1.14 unfrozen water contentthe ratio of the mass ofwater (free and adsorbed) contained in the pore spaces offrozen soil or rock material, to the mass
21、of solid particles inthat material, expressed as percentage (2).3.2 For definitions of other terms used in this test method,refer to Terminology D 653.4. Summary of Test Method4.1 A cylindrical frozen soil specimen is cut to length andthe ends are machined flat. The specimen is placed in a loadingch
22、amber and allowed to stabilize at a desired test temperature.An axial compression stress is applied to the specimen and heldconstant at the specified temperature for the duration of thetest. Specimen deformation is monitored continuously. Typicalresults of a uniaxial compression creep test are shown
23、 in Fig.X1.1.5. Significance and Use5.1 Understanding the mechanical properties of frozen soilsis of primary importance to permafrost engineering. Data fromcreep tests are necessary for the design of most foundationelements embedded in, or bearing on frozen ground. Theymake it possible to predict th
24、e time-dependent settlements ofpiles and shallow foundations under service loads, and toestimate their short- and long-term bearing capacity. Creeptests also provide quantitative parameters for the stabilityanalysis of underground structures that are created for perma-nent use.5.2 It must be recogni
25、zed that the structure of frozen soil insitu and its behavior under load may differ significantly fromthat of an artificially prepared specimen in the laboratory. Thisis mainly due to the fact that natural permafrost ground maycontain ice in many different forms and sizes, in addition to thepore ice
26、 contained in a small laboratory specimen. These largeground-ice inclusions (such as ice lenses) will considerablyaffect the time-dependent behavior of full-scale engineeringstructures.5.3 In order to obtain reliable results, high-quality undis-turbed representative permafrost samples are required f
27、or creeptests. The quality of the sample depends on the type of frozensoil sampled, the in situ thermal condition at the time ofsampling, the sampling method, and the transportation andstorage procedures prior to testing. The best testing programcan be ruined by poor-quality samples. In addition, on
28、e mustalways keep in mind that the application of laboratory resultsto practical problems requires much caution and engineeringjudgment.6. Apparatus6.1 Axial Loading DeviceThe axial compression deviceshall be capable of maintaining a constant load or stress withinone percent of the applied load or s
29、tress. The device may be ascrew jack driven by an electric motor through a gearedtransmission, a platform weighing scale equipped with ascrew-jack-activated load yoke, a deadweight load apparatus, ahydraulic or pneumatic loading device, or any other compres-sion device with sufficient capacity and c
30、ontrol to provide theloading conditions prescribed in Section 8. Vibrations due tothe operation of the loading device should be kept at aminimum.6.2 Axial Load-Measuring DeviceThe axial load-measuring device may be a load ring, electronic load cell,hydraulic load cell, or any other load measuring de
31、vice capableof the accuracy prescribed in this paragraph and may be a partof the axial loading device. For frozen soil with a deviatorstress at failure of less than 100 kPa, the axial loadmeasuringdevice shall be capable of measuring the unit axial load to anaccuracy equivalent to 1 kPa; for frozen
32、soil with a deviatorstress at failure of 100 kPa and greater, the axial load-measuring device shall be capable of measuring the axial loadto an accuracy of 1 % of the axial load at failure.6.3 Measurement of Axial DeformationThe interactionbetween the test specimen and the testing machine loadingsys
33、tem can affect the creep test results. For this reason, in orderto observe the true strain-time behavior of a frozen soilspecimens, deformations should be measured directly on thespecimen. This can be achieved by mounting deformationgages on special holders attached to the sides of the specimen(3).
34、If deformations are measured between the loading platens,it should be recognized that some initial deformation (seatingD 5520 94 (2006)e12error) will occur between the specimen ends and the loadingsurface of the platens.6.4 Bearing SurfacesThe specimen cap and base shall beconstructed of a noncorros
35、ive impermeable material, and eachshall have a circular plane surface of contact with the specimenand a circular cross section. The weight of the specimen capshall be less than 0.5 % of the applied axial load at failure. Thediameter of the cap and base shall be greater than the diameterof the specim
36、en. The stiffness of the end cap should normallybe high enough to distribute the applied load uniformly overthe loading surface of the specimen. The specimen base shallbe coupled to the compression chamber so as to prevent lateralmotion or tilting, and the specimen cap shall be designed toreceive th
37、e piston, such that the piston-to-cap contact area isconcentric with the cap.NOTE 1It is advisable not to use ball or spherical seats that wouldallow rotation of the platens, but rather special care should be taken intrimming or molding the ends of the specimen to parallel planes. The endsof the spe
38、cimen shall be flat to 0.02 mm and shall not depart fromperpendicularity 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 specimendeformation can be tolerated if the height to diameter ratio of the testspecimen is two to three. Howe
39、ver, it is recommended that lubricatedplatens be used whenever possible in the uniaxial compression and creeptesting of frozen soils. The lubricated platen should consist of a circularsheet of 0.8-mm thick latex membrane, attached to the loading face of asteel platen with a 0.5-mm thick layer of hig
40、hvacuum silicone grease. Thesteel platens are polished stainless steel disks about 10 mm larger than thespecimen diameter. As the latex sheets and grease layers compress underload, the axial strain of the specimen should be measured using exten-someters located on the specimen (4, 5).6.5 Thermal Con
41、trolThe compressive strength of frozensoil is also affected greatly by temperature and its fluctuations.It is imperative, therefore, that specimens be stored and testedin a freezing chamber that has only a small temperaturefluctuation to minimize thermal disturbance. Reduce the effectof fluctuations
42、 in temperature by enclosing the specimen in aninsulating jacket during storage and testing. Reference (6)suggests the following permissible temperature variationswhen storing and testing frozen soils within the followingdifferent ranges:Temperature, C 0 to 2 2 to 5 5 to 10 below 10Permissible devia
43、-tion, C60.1 60.2 60.5 61.07. Test Specimen7.1 Thermal Disturbance Effects:7.1.1 The strength and deformation properties of frozen soilsamples are known to be affected by sublimation, evaporation,and thermal disturbance.Their effect is in the redistribution andultimate loss of moisture from the samp
44、le as the result of atemperature gradient or low-humidity environment, or both.Loss of moisture reduces the cohesion between soil particlesand may reduce the strength (that is dependent on tempera-ture). The effects of moisture redistribution in frozen soil arethought to change its strength and cree
45、p behavior.7.1.2 Thermal disturbance of a frozen sample refers not onlyto thawing, but also to temperature fluctuations. Soil structuremay be changed completely if the sample is thawed and thenrefrozen. Temperature fluctuations can set up thermal gradi-ents, causing moisture redistribution and possi
46、ble change in theunfrozen moisture content. Take care, therefore, to ensure thatfrozen soil specimens remain in their natural state, and thatthey are protected against the detrimental effects of sublimationand thermal disturbance until testing is completed.7.1.3 In the event that the soil sample is
47、not maintained atthe in situ temperature prior to testing, bring the test specimento the test temperature from a higher temperature to reduce thehysteresis effect on the unfrozen water content.7.1.4 Before testing, maintain the test specimen at the testtemperature for a sufficient period, to ensure
48、that the tempera-ture is uniform throughout the volume.7.2 Machining and Preparation of Specimens for Testing:7.2.1 The machining and preparation procedures used forfrozen soils depend upon the size and shape of the specimenrequired, the type of soil, and the particular test being per-formed. Follow
49、 similar procedures for cutting and machiningboth naturally frozen and artificially frozen samples.7.2.2 Handle frozen soil samples with gloves and all toolsand equipment kept in the cold room to avoid sample damageby localized thawing. A temperature of 5 6 1C is the mostsuitable ambient temperature for machining with respect tomaterial workability and personal comfort.7.2.3 Cylindrical specimens are either machined on a work-ing lathe or cut carefully with a coring tube in the laboratory.They can also be cored from block samples, using a diamondset
