ASTM D5311-1992(2004) 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测试方法》.pdf

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1、Designation: D 5311 92 (Reapproved 2004)Standard Test Method forLoad Controlled Cyclic Triaxial Strength of Soil1This standard is issued under the fixed designation D 5311; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o

2、f 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.1. Scope1.1 This test method covers the determination of the cyclicstrength (sometimes called the liquefaction potential) of sa

3、tu-rated soils in either undisturbed 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 stressapplica

4、tion, development of excess 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 under und-rained conditions to simulate essentially undrained fie

5、ld con-ditions during earthquake 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 general

6、ly applicable for testingcohesionless free draining soils of relatively high permeability.When testing well-graded materials, silts, or clays, it should berecognized that pore-water pressures monitored at the speci-men ends to not in general represent pore-water pressure valuesthroughout the specime

7、n. However, this test method may befollowed when testing most soil types if care is taken to ensurethat problem soils receive special consideration when testedand when test results are evaluated.1.6 There are certain limitations inherent in using cyclictriaxial tests to simulate the stress and strai

8、n conditions of a soilelement in the field during an earthquake.1.6.1 Nonuniform stress conditions within the test specimenare imposed by the specimen end platens. This can cause aredistribution of void ratio within the specimen during the test.1.6.2 A 90 change in the direction of the major princip

9、alstress occurs during the two halves of the loading cycle onisotropically consolidated specimens.1.6.3 The maximum cyclic shear stress that can be appliedto the specimen is controlled by the stress conditions at the endof consolidation and the pore-water pressures generated duringtesting. For an is

10、otropically consolidated contractive (volumedecreasing) specimen tested in cyclic compression, the maxi-mum cyclic shear stress that can be applied to the specimen isequal to one-half of the initial total axial pressure. Sincecohesionless soils are not capable of taking tension, cyclicshear stresses

11、 greater than this value tend to lift the top platenfrom 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

12、portion of the load cycle, invalidating test resultsbeyond that point.1.6.4 While it is advised that the best possible undisturbedspecimens be obtained for cyclic strength testing, it is some-times necessary to reconstitute soil specimens. It has beenshown that different methods of reconstituting sp

13、ecimens to thesame density may result in significantly different cyclicstrengths. Also, undisturbed specimens will almost always bestronger than reconstituted specimens.1.6.5 The interaction between the specimen, membrane, andconfining fluid has an influence on cyclic behavior. Membranecompliance ef

14、fects cannot be readily accounted for in the testprocedure or in interpretation of test results. Changes inpore-water pressure can cause changes in membrane penetra-tion in specimens of cohesionless soils. These changes cansignificantly influence the test results.1.6.6 The mean total confining press

15、ure is asymmetricduring the compression and extension stress application whenthe chamber pressure is constant. This is totally different fromthe symmetric stress in the simple shear case of the levelground liquefaction.1.7 The values stated in both inch-pound and SI units are tobe regarded separatel

16、y as the standard. The values given inparentheses are for information only.1This test method is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.09 on DynamicProperties of Soils.Current edition approved Oct. 15, 1992. Published January

17、 1993.2The boldface numbers in parentheses refer to a list of references at the end ofthe text.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1.8 This standard does not purport to address all of thesafety concerns, if any, associate

18、d 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:3D 422 Test Method for Particle-Size Analysis of SoilsD 653 Ter

19、minology Relating to Soil, Rock, and ContainedFluidsD 854 Test Method for Specific Gravity of SoilsD 1587 Practice for Thin-Walled Tube Sampling of SoilsD 2216 Test Method for Laboratory Determination of Water(Moisture) Content of Soil and RockD 2850 Test Method for Unconsolidated, Undrained Com-pre

20、ssive Strength of Cohesive Soils in Triaxial Compres-sionD 4220 Practice for Preserving and Transporting SoilSamplesD 4253 Test Methods for Maximum Index Density and UnitWeight of Soils Using a Vibratory TableD 4254 Test Method for Minimum Index Density and UnitWeight of Soils and Calculation of Rel

21、ative DensityD 4318 Test Method for Liquid Limit, Plastic Limit, andPlasticity Index of SoilsD 4767 Test Method for Consolidated-Undrained TriaxialCompression Test on Cohesive Soils3. Terminology3.1 Definitions:3.1.1 Definitions for terms used in this test method (includ-ing liquefaction) are in acc

22、ordance with Terminology D 653.Additional descriptions of terms are defined in 3.2 and in 10.2and Fig. 1.3.2 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 peak pore pressure ratiothe maximum pore pressureratio measured

23、 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 amplitude) strain the differ-ence between the maximum axial s

24、train 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, s83c, at the end of primaryconsolidation.4. Summary of Test M

25、ethod4.1 A cylindrical soil specimen is sealed in a watertightrubber 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).

26、 Tubing connections to the top and bottomspecimen platens permit 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

27、 connected to the specimen top platen. The cyclic load,specimen 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 cycl

28、ic loadinggenerally causes an increase in the pore-water pressure 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 confini

29、ng pressure,full or 100 % pore pressure ratio (sometimes called 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 a

30、soil mass due to earthquake or other cyclic loading.5.1.1 Cyclic 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 tes

31、ts may be performed at asingle effective confining pressure, usually equal to 14.5 lb/in.2(100 kN/m2), or alternate pressures as appropriate on isotro-pically consolidated specimens to compare cyclic strengthresults for a particular soil type with that of other soils, Ref (2).5.2 The cyclic triaxial

32、 test is a commonly used technique fordetermining cyclic soil strength.5.3 Cyclic strength depends upon many factors, includingdensity, confining pressure, applied cyclic shear stress, stress3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serv

33、iceastm.org. For Annual Book of ASTMStandardsvolume information, refer to the standards Document Summary page onthe ASTM website.FIG. 1 Schematic Representation of Load-Controlled CyclicTriaxial Strength Test EquipmentD 5311 92 (2004)2history, grain structure, age of soil deposit, specimen prepara-t

34、ion procedure, and the frequency, uniformity, and shape of thecyclic wave form. Thus, close attention must be given totesting details and equipment.6. Apparatus6.1 In many ways, triaxial equipment suitable for cyclictriaxial strength tests is similar to equipment used for theunconsolidated-undrained

35、 triaxial compression test (see TestMethod D 2850) and the consolidated-undrained triaxial com-pression test (see Test Method D 4767). However, there arespecial features described in the following subsections that arerequired to perform acceptable cyclic triaxial tests. A schematicrepresentation of

36、a typical load-controlled cyclic triaxialstrength test set-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 should beused to guide

37、the load rod to minimize friction and to maintainalignment.6.2.2 The load rod diameter should 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 cel

38、ldesign for cyclic soils testing. The seal must exert negligiblefriction 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

39、proposed in Ref (3) will meet or exceed theserequirements.6.2.4 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 alignmen

40、tbefore placement of the chamber have been found to work wellat 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 triax

41、ial tests extension as well ascompression loads may be exerted 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.6.2.6 There shall be provision for specimen drainage at boththe top and bottom pla

42、tens.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 of fine sand(3.9 3 105in./s 1 3 104cm/s). The discs shall be regular

43、lychecked to determine whether they have become clogged.6.3 Dynamic loading equipment used for load-controlledcyclic triaxial tests shall be capable of applying a uniformsinusoidal load at a frequency range of 0.1 to 2.0 Hz. Thefrequency of 1.0 Hz is preferred. The loading device shall beable to mai

44、ntain uniform cyclic loadings to at least 20 %peak-to-peak strains. Unsymmetrical compression-extensionload peaks, nonuniformity of pulse duration,“ ringing,” or loadfall-off at large strains shall not exceed tolerance illustrated inFig. 3. The equipment shall also be able to apply the cyclic loadab

45、out an initial static load on the loading rod. Evaluateuniformity of the load trace into the failure state to ensure thatload uniformity criteria presented in previous sections areachieved. Show this in an appropriate way by calculating thepercent load drift (Perror) between the maximum load (DPmax)

46、based on the initial loading cycle and the measured load in thenth cycle as follows:D Pmax5 DPc1DPe!max(1)Perror5DPc1DPe!max2 DP 1DPe!n# 3 100DPc1DPe!maxPerrorshould be 5 % at axial strains of 6 5%.NOTE 1(a) Eccentricity and (b) parallelism.FIG. 2 Limits on Acceptable Platen and Load Rod AlignmentD

47、5311 92 (2004)3where:DPmax= maximum load,DPc= change in peak applied load in compression,DPe= change in peak applied load in extension, andPerror= percent load drift.NOTE 1For less than 20 cycles for samples with high fines contentnon-uniform pore pressure distribution may result.6.4 Recording Equip

48、mentLoad, displacement, and porewater pressure transducers are required to monitor specimenbehavior during cyclic loading; provisions for monitoring thechamber pressure during loading are optional (see Table 1).6.4.1 Axial Load MeasurementThe desired maximum cy-clic load-measuring device may be a lo

49、ad ring, electronic loadcell, hydraulic load cell, or any other load-measuring devicecapable of measuring the axial load to an accuracy of within 61 % of the axial load. Generally, the load cell capacity shouldbe no greater than five times the total maximum load applied tothe test specimen to ensure that the necessary measurementaccuracy is achieved. The minimum performance characteris-tics of the load cell are presented in Table 1.6.4.2 Axial Deformation Measurement Displacementmeasuring devices such as linear variable differential trans-former (LVDT), potenti