ASTM D5520-2018 Standard Test Method for Laboratory Determination of Creep Properties of Frozen Soil Samples by Uniaxial Compression.pdf

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1、Designation: D5520 18Standard 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 oninterparticle friction, particle interlocking,

5、 and cohesion. In frozen soil, however, bonding of particlesby ice may be the dominant strength factor. The strength of ice in frozen soil is dependent on manyfactors, such as temperature, pressure, strain rate, grain size, crystal orientation, and density. In ice-richsoils (that is, soils where the

6、 ratio of the mass of ice contained in the pore spaces of frozen soil or rockmaterial, to the mass of solid particles in that material is high), frozen soil behavior under load issimilar to that of ice. In fact, for fine-grained soils, experimental data suggest that the ice matrixdominates when mine

7、ral 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 playan important role, especially in fine-grained soils. Finally, for frozen sand, maximum strength isattained at full ice s

8、aturation and maximum dry density (1).21. Scope*1.1 This test method covers the determination of the creepbehavior of cylindrical specimens of frozen soil, subjected touniaxial compression. It specifies the apparatus,instrumentation, and procedures for determining the stress-strain-time, or strength

9、 versus strain rate relationships forfrozen soils under deviatoric creep conditions.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

10、as stress-relaxation tests, simpleshear tests, and beam flexure tests. Creep testing under triaxialtest conditions will be covered in another standard.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 calc

11、ulated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.4.1 For the purposes of comparing, a measured or calcu-lated value(s) with specified limits, the measured or calculatedvalue(s) shall be rounded to the nearest decimal or significantdigits

12、 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 theindustry standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider mat

13、erial variation, purpose forobtaining the data, special purpose studies, or any consider-ations for the users objectives; and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations. It is beyond the scopeof this standard to consider

14、 significant digits used in analysismethods for engineering design.1This 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. 15, 2018. Published December 2018. Origina

15、llyapproved in 1994. Last previous edition approved in 2011 as D552011. DOI:10.1520/D5520-18.2The boldface numbers in parentheses refer to the list of references at the end ofthe text.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive

16、, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issu

17、ed by the World Trade Organization Technical Barriers to Trade (TBT) Committee.11.5 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 to establish appro-priate safety, health, and environmental p

18、ractices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides

19、 and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3D653 Terminology Relating to Soil, Rock, and ContainedFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of S

20、oil and Rock asUsed in Engineering Design and ConstructionD4083 Practice for Description of Frozen Soils (Visual-Manual Procedure)D6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 Definitions:3.1.1 For definitions of common technical terms in thisstandard, refer to Ter

21、minology D653.3.1.2 Definitions of the components of freezing and thawingsoils shall be in 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

22、 et al(2).3.2.2 creep, nof frozen ground, the irrecoverable time-dependent deviatoric deformation that results from long-termapplication of a deviatoric stress.3.2.3 ice-rich permafrost, npermafrost containing excessice.3.2.4 pore ice, nice occurring in the pores of soil androcks.3.2.5 total water c

23、ontent, nthe 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 in thatmaterial, expressed as percentage.3.2.6 unfrozen water content, nthe ratio of the mass ofwater (free and adsorbed) contained in the pore sp

24、aces offrozen soil or rock material, to the mass of solid particles inthat material, expressed as percentage (3).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 loadingchamber and allowed to stabilize at a de

25、sired 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 in Fig.X1.1.5. Significance and Use5.

26、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 the time-dependent settlements ofpiles a

27、nd 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 recognized that the structure of frozen soil

28、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 contained in a small laboratory speci

29、men. These largeground-ice inclusions (such as ice lenses, a dominanthorizontal, lens-shaped body of ice of any dimension) willconsiderably affect the time-dependent behavior of full-scaleengineering structures.5.3 In order to obtain reliable results, high-quality intactrepresentative permafrost sam

30、ples 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 storageprocedures prior to testing. The best testing program can beruined by poor-quality sampl

31、es. In addition, one must alwayskeep in mind that the application of laboratory results topractical problems requires much caution and engineeringjudgment.NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the

32、 equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing/sampling/inspection/etc. Users of this standard arecautioned that compliance with Practice D3740 does not in itself assurereliable results. Reliable res

33、ults 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 of maintaining a constant load or stress withinone percent of the applied load or stress. The device may be ascrew jack dri

34、ven 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 control to provide the3For referenced AST

35、M 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.D5520 182loading conditions prescribed in Section 8. Vibrations due tothe operat

36、ion 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 device capableof the accuracy prescribed in this paragraph and may be a partof the axial loadi

37、ng device. For frozen soil with a deviatorstress at failure of less than 100 kPa, the axial load measuringdevice shall be capable 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 devic

38、e 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 loadingsystem can affect the creep test results. For this reason, in orderto observe the true strain-t

39、ime 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(4). If deformations are measured between the loading platens,it should be recognized that some i

40、nitial deformation (seatingerror) will occur between the specimen ends and the loadingsurface of the platens.6.4 Bearing SurfacesThe specimen cap and base shall beconstructed of a noncorrosive impermeable material, and eachshall have a circular plane surface of contact with the specimenand a circula

41、r 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 specimen. The stiffness of the end cap should normallybe high enough to distribute the applied load uniformly overthe

42、 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 the piston, such that the piston-to-cap contact area isconcentric with the cap.NOTE 2It is advisable not to use b

43、all 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 specimen shall be flat to 0.02 mm and shall not depart fromperpendicularity to the axis of the specimen by more th

44、an 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. However, it is recommended that lubricatedplatens be used whenever possible in the uniaxial compression and creepte

45、sting 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 high vacuum silicone grease. Thesteel platens are polished stainless steel disks about 10 mm larger than thespecim

46、en 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 (5, 6).6.5 Thermal ControlThe compressive strength of frozensoil is also affected greatly by temperature and its fluctuations.It is

47、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 in temperature by enclosing the specimen in aninsulating jacket during storage and testing. Reference (7)sugg

48、ests 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 10Permissibledeviation, C0.1 0.2 0.5 1.07. Test Specimen7.1 Thermal Disturbance Effects:7.1.1 The strength and deformation proper

49、ties 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 sample 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 creep behavior.7.1.2 Thermal disturbance of a frozen sample refers not onlyto tha