ASTM D5311-2011 Standard Test Method for Load Controlled Cyclic Triaxial Strength of Soil《土壤的负荷控制三向疲劳强度的标准试验方法》.pdf

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1、Designation: D5311 11Standard Test Method forLoad Controlled Cyclic Triaxial Strength of Soil1This standard is issued under the fixed designation D5311; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A n

2、umber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the cyclicstrength (sometimes called the liquefaction potential) of satu-rated soils in ei

3、ther intact or reconstituted states by theload-controlled cyclic triaxial technique.1.2 The cyclic strength of a soil is evaluated relative to anumber of factors, including: the development of axial strain,magnitude of applied cyclic stress, number of cycles of stressapplication, development of exce

4、ss pore-water pressure, andstate of effective stress. A comprehensive review of factorsaffecting cyclic triaxial test results is contained in the literature(1).21.3 Cyclic triaxial strength tests are conducted underundrained conditions to simulate essentially undrained fieldconditions during earthqu

5、ake or other cyclic loading.1.4 Cyclic triaxial strength tests are destructive. Failure maybe defined on the basis of the number of stress cycles requiredto reach a limiting strain or 100 % pore pressure ratio. SeeSection 3 for Terminology.1.5 This test method is generally applicable for testingcohe

6、sionless free draining soils of relatively high permeability.When testing well-graded materials, silts, or clays, pore-waterpressures monitored at the specimen ends may not representpore-water pressure values throughout the specimen. However,this test method may be followed when testing most soil ty

7、pesif care is taken to ensure that problem soils receive specialconsideration when tested and when test results are evaluated.1.6 The values stated in either SI units or inch-pound unitspresented in brackets are to be regarded separately asstandard. The values stated in each system may not be exacte

8、quivalents; therefore, each system shall be used independentlyof the other. Combining values from the two systems mayresult in non-conformance with the standard. Reporting of testresults in units other than SI shall not be regarded as noncon-formance with this test method.1.7 All observed and calcul

9、ated values shall conform to theguide for significant digits and rounding established in PracticeD6026. The procedures in Practice D6026 that are used tospecify how data are collected, recorded, and calculated areregarded as the industry standard. In addition, they are repre-sentative of the signifi

10、cant digits that should generally beretained. The procedures do not consider material variation,purpose for obtaining the data, special purpose studies, or anyconsiderations for the objectives of the user. Increasing orreducing the significant digits of reported data to be commen-surate with these c

11、onsiderations is common practice. Consid-eration of the significant digits to be used in analysis methodsfor engineering design is beyond the scope of this standard.1.7.1 The method used to specify how data are collected,calculated, or recorded in this standard is not directly related tothe accuracy

12、 to which the data can be applied in design or otheruses, or both. How one applies the results obtained using thisstandard is beyond its scope.1.8 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 standar

13、d 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:3D422 Test Method for Particle-Size Analysis of SoilsD653 Terminology Relating to Soil, Rock, and ContainedFluidsD854 Test Methods

14、 for Specific Gravity of Soil Solids byWater PycnometerD1587 Practice for Thin-Walled Tube Sampling of Soils forGeotechnical PurposesD2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD2850 Test Method for Unconsolidated-Undrained TriaxialCompression

15、 Test on Cohesive SoilsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4220 Practices for Preserving and Transporting SoilSamples1This test method is under the jurisdiction ofASTM Committee D18 on

16、 Soil andRock and is the direct responsibility of Subcommittee D18.09 on Cyclic andDynamic Properties of Soils.Current edition approved Nov. 1, 2011. Published January 2012. Originallyapproved in 1992. Last previous edition approved in 2004 as D531192(2004)1.DOI: 10.1520/D5311-11.2The boldface numbe

17、rs in parentheses refer to a list of references at the end ofthe text.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandardsvolume information, refer to the standards Document Summary page onthe ASTM

18、website.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 States.D4253 Test Methods for Maximum Index Density and UnitWeight of Soils Using a Vibratory TableD4254 Test Methods

19、for Minimum Index Density and UnitWeight of Soils and Calculation of Relative DensityD4318 Test Methods for Liquid Limit, Plastic Limit, andPlasticity Index of SoilsD4767 Test Method for Consolidated Undrained TriaxialCompression Test for Cohesive SoilsD6026 Practice for Using Significant Digits in

20、GeotechnicalData3. Terminology3.1 Definitions:3.1.1 Definitions for terms used in this test method (includ-ing liquefaction) are in accordance with Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 full or 100 % pore pressure ratio a condition inwhich Du equals s83c.3.2.2 pea

21、k pore pressure ratiothe maximum pore pressureratio measured during a particular loading sequence.3.2.3 peak (single amplitude) strainthe maximum axialstrain (from the origin or initial step) in either compression orextension produced during a particular loading sequence.3.2.4 peak to peak (double a

22、mplitude) strain the differ-ence between the maximum axial strain in compression andextension during a given cycle under cyclic loading conditions.3.2.5 pore pressure ratiothe ratio, expressed as a percent-age, of the change of excess pore-water pressure, D u,totheeffective minor principal stress, s

23、83c, at the end of primaryconsolidation.3.2.6 cyclic stress ratiothe ratio of the applied deviatorstress to the effective confining pressure (incorporatingchanges in excess pore water pressure) during cyclic loading.4. Summary of Test Method4.1 A cylindrical soil specimen is sealed in a watertightru

24、bber membrane and confined in a triaxial chamber where itis subjected to a confining pressure. An axial load is applied tothe top of the specimen by a load rod.4.2 Specimens are consolidated isotropically (equal axialand radial stress). Tubing connections to the top and bottomspecimen platens permit

25、 flow of water during saturation,consolidation and measurement of pore-water pressure duringcyclic loading.4.3 Following saturation and consolidation, the specimen issubjected to a sinusoidally varying axial load by means of theload rod connected to the specimen top platen. The cyclic load,specimen

26、axial deformation, and porewater pressure develop-ment with time are monitored.4.4 The test is conducted under undrained conditions toapproximate essentially undrained field conditions duringearthquake or other dynamic loading. The cyclic loadinggenerally causes an increase in the pore-water pressur

27、e in thespecimen, resulting in a decrease in the effective stress and anincrease in the cyclic axial deformation of the specimen.4.5 Failure may be defined as when the peak excess pore-water pressure equals the initial effective confining pressure,full or 100 % pore pressure ratio (sometimes called

28、initialliquefaction), or in terms of a limiting cyclic strain or perma-nent strain.5. Significance and Use5.1 Cyclic triaxial strength test results are used for evaluat-ing the ability of a soil to resist the shear stresses induced in asoil mass due to earthquake or other cyclic loading.5.1.1 Cyclic

29、 triaxial strength tests may be performed atdifferent values of effective confining pressure on isotropicallyconsolidated specimens to provide data required for estimatingthe cyclic stability of a soil.5.1.2 Cyclic triaxial strength tests may be performed at asingle effective confining pressure, usu

30、ally equal to 100 kN/m2(14.5 lb/in.2), or alternate pressures as appropriate on isotropi-cally consolidated specimens to compare cyclic strength resultsfor a particular soil type with that of other soils, Ref (2).5.2 The cyclic triaxial test is a commonly used technique fordetermining cyclic soil st

31、rength.5.3 Cyclic strength depends upon many factors, includingdensity, confining pressure, applied cyclic shear stress, stresshistory, grain structure, age of soil deposit, specimen prepara-tion procedure, and the frequency, uniformity, and shape of thecyclic wave form. Thus, close attention must b

32、e given totesting details and equipment.5.4 There are certain limitations inherent in using cyclictriaxial tests to simulate the stress and strain conditions of a soilelement in the field during an earthquake.5.4.1 Nonuniform stress conditions within the test specimenare imposed by the specimen end

33、platens. This can cause aredistribution of void ratio within the specimen during the test.5.4.2 A 90 change in the direction of the major principalstress occurs during the two halves of the loading cycle onisotropically consolidated specimens.5.4.3 The maximum cyclic shear stress that can be applied

34、to the specimen is controlled by the stress conditions at the endof consolidation and the pore-water pressures generated duringtesting. For an isotropically consolidated contractive (volumedecreasing) specimen tested in cyclic compression, the maxi-mum cyclic shear stress that can be applied to the

35、specimen isequal to one-half of the initial total axial pressure. Sincecohesionless soils are not capable of taking tension, cyclicshear stresses greater than this value tend to lift the top platenFIG. 1 Schematic Representation of Load-Controlled CyclicTriaxial Strength Test EquipmentD5311 112from

36、the soil specimen. Also, as the pore-water pressureincreases during tests performed on isotropically consolidatedspecimens, the effective confining pressure is reduced, contrib-uting to the tendency of the specimen to neck during theextension portion of the load cycle, invalidating test resultsbeyon

37、d that point.5.4.4 While it is advised that the best possible intactspecimens be obtained for cyclic strength testing, it is some-times necessary to reconstitute soil specimens. It has beenshown that different methods of reconstituting specimens to thesame density may result in significantly differe

38、nt cyclicstrengths. Also, intact specimens will almost always be stron-ger than reconstituted specimens.5.4.5 The interaction between the specimen, membrane, andconfining fluid has an influence on cyclic behavior. Membranecompliance effects cannot be readily accounted for in the testprocedure or in

39、interpretation of test results. Changes inporewater pressure can cause changes in membrane penetrationin specimens of cohesionless soils. These changes can signifi-cantly influence the test results.5.4.6 The mean total confining pressure is asymmetricduring the compression and extension stress appli

40、cation whenthe chamber pressure is constant. This is totally different fromthe symmetric stress in the simple shear case of the levelground liquefaction.NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the e

41、quipment 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 resul

42、ts depend on many factors; Practice D3740provides a means of evaluating some of those factors.6. Apparatus6.1 In many ways, triaxial equipment suitable for cyclictriaxial strength tests is similar to equipment used for theunconsolidated-undrained triaxial compression test (see TestMethod D2850) and

43、the consolidated-undrained triaxial com-pression test (see Test Method D4767). However, there arespecial features described in the following subsections that arerequired to perform acceptable cyclic triaxial tests.Aschematicrepresentation of a typical load-controlled cyclic triaxialstrength test set

44、-up is shown in Fig. 1.6.2 Triaxial Compression CellThe primary considerationsin selecting the cell are tolerances for the piston, top cap, andlow friction piston seal.6.2.1 Two linear ball bushings or similar bearings shall beused to guide the load rod to minimize friction and to maintainalignment.

45、6.2.2 The load rod diameter shall be large enough tominimize lateral bending. A minimum load rod diameter of16the specimen diameter has been used successfully in manylaboratories.6.2.3 The load rod seal is a critical element in triaxial celldesign for cyclic soils testing. The seal must exert neglig

46、iblefriction on the load rod. The maximum acceptable pistonfriction tolerable without applying load corrections is com-monly considered to be 6 2 % of the maximum singleamplitude cyclic load applied in the test. The use of an airbushing as proposed in Ref (3) will meet or exceed theserequirements.6.

47、2.4 Top and bottom platen alignment is critical if prema-ture specimen failure caused by the application of a nonuni-form state of stress to the specimen is to be avoided. Internaltie-rod triaxial cells that allow for adjustment of alignmentbefore placement of the chamber have been found to work wel

48、lat a number of laboratories. These cells allow the placement ofthe cell wall after the specimen is in place between the loadingplatens.Acceptable limits of platen eccentricity and parellelismare shown in Fig. 2.6.2.5 Since in cyclic triaxial tests extension as well ascompression loads may be exerte

49、d on the specimen, the loadrod shall be connected to the top platen by straight threadsbacked by a shoulder on the piston that tightens up against theplaten.FIG. 2 Limits on Acceptable Platen and Load Rod Alignment(a) Eccentricity and (b) ParallelismD5311 1136.2.6 There shall be provision for specimen drainage at boththe top and bottom platens.6.2.7 Porous DiscsThe specimen shall be separated fromthe specimen cap and base by rigid porous discs of a diameterequal to that of the specimen. The coefficient of permeability ofthe discs shall be approximately equal to that o