1、Designation: D5520 11Standard Test Method forLaboratory Determination of Creep Properties of Frozen SoilSamples by Uniaxial Compression1This standard is issued under the fixed designation D5520; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONKnowledge of the stress-strain-strength behavior of frozen soil is of great importance for civ
3、ilengineering 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 much more subject to creep and relaxation effects, and their behavior
4、 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 frozen soils depends on interparticlefriction, particle interlocking,
5、 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, crystal orientation, and density. At very high icecontents (ice-rich soils),
6、 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, (ice-poor soils), when interparticleforces begin to contribute to str
7、ength, 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. Scope*1.1 This test method covers the determination of the creepbehavior of cylindrical specimens of f
8、rozen 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 conditions.1.2 Although this test method is one that is most commonlyu
9、sed, 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. Creep testing under triaxialtest conditions will be covered in another s
10、tandard.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.4.1 For the purposes of compari
11、ng, a measured or calcu-lated value(s) with specified limits, the measured or calculatedvalue(s) shall be rounded to the nearest decimal or significantdigits 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 th
12、eindustry standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider-ations for the users objectives; and it is common prac
13、tice toincrease or reduce significant digits of reported data to be1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.19 on Frozen Soils andRock.Current edition approved Nov. 1, 2011. Published January 2012. Originall
14、yapproved in 1994. Last previous edition approved in 2006 as D552094(2006)1.DOI: 10.1520/D5520-11.2The boldface numbers in parentheses refer to the list of references at the end ofthe text.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbo
15、r Drive, PO Box C700, West Conshohocken, PA 19428-2959, United Smensurate with these considerations. It is beyond the scopeof this standard to consider significant digits used in analysismethods for engineering design.1.5 This standard does not purport to address all of thesafety concerns, if any, a
16、ssociated with its use. It is theresponsibility of the user of this standard 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:3D653 Terminology Relating to Soil, Rock, and Contained
17、FluidsD2850 Test Method for Unconsolidated-Undrained TriaxialCompression Test on Cohesive SoilsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4083 Practice for Description of Frozen Soils (Visual
18、Manual Procedure)D4341 Test Method for Creep of Hard Rock Core Speci-mens in Uniaxial Compression at Ambient or ElevatedTemperature4D4405 Test Method for Creep of Soft Rock Core Specimensin Uniaxial Compression atAmbient or Elevated Tempera-ture4D4406 Test Method for Creep of Rock Core Specimens in
19、Triaxial Compression at Ambient or Elevated Tempera-tures4D6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 Definitions:3.1.1 For definitions of terms in this standard, refer toTerminology D653.3.1.2 Definitions of the components of freezing and thawingsoils shall be i
20、n accordance with the terminology in PracticeD4083.3.2 Definitions of Terms Specific to This Standard:3.2.1 The following terms supplement those in PracticeD4083 and in the glossary on permafrost terms by Harris et al(17).3.2.2 creepof frozen ground, the irrecoverable time-dependent deviatoric defor
21、mation that results from long-termapplication of a deviatoric stress.3.2.3 excess icethe volume of ice in the ground whichexceeds the total pore volume that the ground would haveunder unfrozen conditions.3.2.4 ground icea general term referring to all types of iceformed in freezing or frozen ground.
22、3.2.5 ice-bearing permafrostpermafrost that contains ice.3.2.6 ice-bonded permafrostice-bearing permafrost inwhich the soil particles are cemented together by ice.3.2.7 ice contentthe ratio of the mass of ice contained inthe pore spaces of frozen soil or rock material, to the mass ofsolid particles
23、in that material, expressed as percentage.3.2.8 ice lensa dominant horizontal, lens-shaped body ofice of any dimension.3.2.9 ice-rich permafrostpermafrost containing excessice.3.2.10 permafrostperennially frozen soil or rock.3.2.11 pore iceice occurring in the pores of soil and rocks.3.2.12 samplea
24、portion of a material intended to berepresentative of the whole.3.2.13 specimena piece or portion of a sample used tomake a test.3.2.14 total water contentthe ratio of the mass of water(unfrozen water + ice) contained in the pore spaces of frozensoil or rock material, to the mass of solid particles
25、in thatmaterial, expressed as percentage.3.2.15 unfrozen water contentthe ratio of the mass ofwater (free and adsorbed) contained in the pore spaces offrozen soil or rock material, to the mass of solid particles inthat material, expressed as percentage (2).4. Summary of Test Method4.1 A cylindrical
26、frozen soil specimen is cut to length andthe ends are machined flat. The specimen is placed in a loadingchamber 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. Spe
27、cimen deformation is monitored continuously. Typicalresults of a uniaxial compression creep test are shown 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 desi
28、gn of most foundationelements embedded in, or bearing on frozen ground. Theymake it possible to predict the 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
29、the stabilityanalysis of underground structures that are created for perma-nent use.5.2 It must be recognized 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 t
30、hat natural permafrost ground maycontain ice in many different forms and sizes, in addition to thepore ice 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 or
31、der to obtain reliable results, high-quality intactrepresentative permafrost samples are required for creep tests.The quality of the sample depends on the type of frozen soilsampled, the in situ thermal condition at the time of sampling,the sampling method, and the transportation and storage3For ref
32、erenced 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. The last approved version of this historical standard is
33、referencedon www.astm.org.D5520 112procedures prior to testing. The best testing program can beruined by poor-quality samples. In addition, one must alwayskeep in mind that the application of laboratory results topractical problems requires much caution and engineeringjudgment.NOTE 1The quality of t
34、he result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing/sampling/inspection/etc. User
35、s of this standard arecautioned that compliance with Practice D3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D3740provides a means of evaluating some of those factors.6. Apparatus6.1 Axial Loading DeviceThe axial compression deviceshall be capable
36、of maintaining a constant load or stress withinone percent of the applied load or stress. 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 pneuma
37、tic loading device, or any other compres-sion device with sufficient capacity and control 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
38、load ring, electronic load cell,hydraulic load cell, or any other load measuring device 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 load measuringdevice shall be cap
39、able of measuring the unit axial load to anaccuracy equivalent to 1 kPa; for frozen soil with a deviatorstress at failure of 100 kPa and greater, the axial loadmeasuring device shall be capable of measuring the axial loadto an accuracy of 1 % of the axial load at failure.6.3 Measurement of Axial Def
40、ormationThe interactionbetween the test specimen and the testing machine loadingsystem 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 moun
41、ting deformationgages on special holders attached to the sides of the specimen(3). If deformations are measured between the loading platens,it should be recognized that some initial deformation (seatingerror) will occur between the specimen ends and the loadingsurface of the platens.6.4 Bearing Surf
42、acesThe specimen cap and base shall beconstructed of a noncorrosive 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
43、the cap and base shall be greater than the diameterof the specimen. 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
44、 or tilting, and the specimen cap shall be designed toreceive the piston, such that the piston-to-cap contact area isconcentric with the cap.NOTE 2It 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
45、 the ends of the specimen to parallel planes. The endsof the specimen 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 he
46、ight to diameter ratio of the testspecimen is two to three. However, 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 th
47、e loading face of asteel platen with a 0.5-mm thick layer of high vacuum 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 us
48、ing exten-someters located on the specimen (4, 5).6.5 Thermal ControlThe 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
49、to minimize thermal disturbance. Reduce the effectof fluctuations 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-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 sublimatio
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