1、Designation: D7300 11Standard Test Method forLaboratory Determination of Strength Properties of FrozenSoil at a Constant Rate of Strain1This standard is issued under the fixed designation D7300; 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 thestrength behavior of cylindrical specimens o
8、f frozen soil,subjected to uniaxial compression under controlled rates ofstrain. It specifies the apparatus, instrumentation, and proce-dures for determining the stress-strain-time, or strength versusstrain rate relationships for frozen soils under deviatoric creepconditions.1.2 Values stated in SI
9、units are to be regarded as thestandard.1.3 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.3.1 For the purposes of comparing measured or calculatedvalue(s) with specified limits, the measured or calculatedvalue(s)
10、shall be rounded to the nearest decimal or significantdigits in the specified limits.1.3.2 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
11、 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 practice toincrease or reduce significant digits of reported data to be1This test method is under th
12、e 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. Originallyapproved in 2006. Last previous edition approved in 2006 as D730006. DOI:10.1520/D7300-11.2The
13、boldface numbers in parentheses refer to the list of references at the end ofthis standard.1*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 Smensurate with these consideration
14、s. It is beyond the scopeof this standard to consider significant digits used in analyticalmethods for engineering design.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 to establish appro-
15、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 ContainedFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection o
16、f Soil 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
17、Terminology 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 are used in conjunction with thedetermination of the strength properties of froz
18、en soils andsupplement those in Practice D4083 and in the glossary onpermafrost terms by Harris et al (2).3.2.2 creep of frozen groundthe irrecoverable time-dependent deviatoric deformation that results from long-termapplication of a deviatoric stress.3.2.3 excess icethe volume of ice in the ground
19、whichexceeds the total pore volume that the ground would haveunder unfrozen conditions.3.2.4 failurethe stress condition at failure for a testspecimen. Failure is often taken to correspond to the maximumprincipal stress difference (maximum deviator stress) attained,or the principal stress difference
20、 (deviator stress) at 15 % axialstrain, whichever is obtained first during the performance of atest. Depending on frozen soil behavior and field application,other suitable failure criteria may be defined, such as theprincipal stress difference (deviator stress) at a selected axialstrain or strain ra
21、te.3.2.5 ground icea general term referring to all types of iceformed in freezing or frozen ground.3.2.6 ice-bearing permafrostpermafrost that contains ice.3.2.7 ice-bonded permafrostice-bearing permafrost inwhich the soil particles are cemented together by ice.3.2.8 ice contentthe ratio of the mass
22、 of ice contained inthe pore spaces of frozen soil or rock material, to the mass ofsolid particles in that material, expressed as percentage.3.2.9 ice lensa dominant horizontal, lens-shaped body ofice of any dimension.3.2.10 ice-rich permafrostpermafrost containing excessice.3.2.11 permafrostsoil or
23、 rock that remains frozen (tem-perature 0C) for a period of two or more years.3.2.12 pore iceice occurring in the pores of soil and rocks.3.2.13 samplepiece or quantity of bulk material that hasbeen selected by some sampling process.3.2.14 specimenpieces or quantity taken or prepared froma sample fo
24、r testing.3.2.15 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 in thatmaterial, expressed as percentage.3.2.16 unfrozen water contentthe ratio of the mass ofwater (free and adsorbed)
25、 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 frozen soil specimen is cut to length andthe ends are machined flat. The specimen is placed in a loadingchamber and all
26、owed to stabilize at a desired test temperature.Astrain rate in compression is applied to the specimen and heldconstant at the specified temperature for the duration of thetest. Axial stress and deformation of the specimen are moni-tored continuously. Typical results of a set of uniaxial com-pressio
27、n tests are shown in Fig. X1.1 (3).5. Significance and Use5.1 Understanding the mechanical properties of frozen soilsis of primary importance to frozen ground engineering. Datafrom strain rate controlled compression tests are necessary forthe design of most foundation elements embedded in, orbearing
28、 on frozen ground. They make it possible to predict thetime-dependent settlements of piles and shallow foundationsunder service loads, and to estimate their short and long-termbearing capacity. Such tests also provide quantitative param-eters for the stability analysis of underground structures that
29、are created for permanent or semi-permanent 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 that natural permafrost ground maycon
30、tain 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 order to obtain reliable results, high
31、-quality intactrepresentative permafrost samples are required for compres-sion strength tests. The quality of the sample depends on thetype of frozen soil sampled, the in situ thermal condition at thetime of sampling, the sampling method, and the transportationand storage procedures prior to testing
32、. The best testing3For 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.D7300 112program can be ruined by poor-qual
33、ity samples. In addition,one must always keep in mind that the application of laboratoryresults to practical problems requires much caution and engi-neering judgment.NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitabi
34、lity of the 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. R
35、eliable 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 of maintaining a constant strain rate within onepercent of the applied strain rate. The device may be a screwjac
36、k 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 hydraulicor pneumatic loading device, or any other compression devicewith sufficient capacity and control to provide the loadingconditi
37、ons prescribed in Section 8. Vibrations due to theoperation of the loading device should be kept at a minimum.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 prescri
38、bed 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 capable of measuring the unit axial load to anaccuracy equivalent to 1 kPa; for frozen soil with a deviatorstress at fail
39、ure 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 loadingsystem can affect the test results. F
40、or this reason, in order toobserve the true stress-strain-rate behavior of a frozen soilspecimen, 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 betwe
41、en 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 SurfacesThe specimen cap and base shall beconstructed of a noncorrosive impermeable material, and eachshall have a circul
42、ar 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 specimen. The stiffness of the end cap should normallybe hi
43、gh 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 the piston, such that the piston-to-cap contact area is
44、concentric 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 the ends of the specimen to parallel planes. The endsof the specimen shall be flat to 0.02 mm and shall not depart f
45、romperpendicularity 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. However, it is recommended that lubricatedplatens be used
46、 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 high-vacuum silicone grease. Thesteel platens are polish
47、ed 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 (5, 6).6.5 Thermal ControlThe compressive strength of frozensoil is also a
48、ffected 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 in temperature by enclosing the specimen in aninsul
49、ating jacket during storage and testing. Reference (7)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 deviation, C 60.1 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
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