1、Designation: D7928 17Standard Test Method forParticle-Size Distribution (Gradation) of Fine-Grained SoilsUsing the Sedimentation (Hydrometer) Analysis1This standard is issued under the fixed designation D7928; the number immediately following the designation indicates the year oforiginal adoption or
2、, in the case of 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.1. Scope1.1 This test method covers the quantitative determinationof the distribution of pa
3、rticle sizes of the fine-grained portionof soils. The sedimentation or hydrometer method is used todetermine the particle-size distribution (gradation) of thematerial that is finer than the No. 200 (75-m) sieve and largerthan about 0.2-m. The test is performed on material passingthe No. 10 (2.0-mm)
4、or finer sieve and the results are presentedas the mass percent finer versus the log of the particle diameter.1.2 This method can be used to evaluate the fine-grainedfraction of a soil with a wide range of particle sizes bycombining the sedimentation results with a sieve analysisresulting in the com
5、plete gradation curve. The method can alsobe used when there are no coarse-grained particles or when thegradation of the coarse-grained material is not required or notneeded.NOTE 1The significant digits recorded in this test method precludeobtaining the grain size distribution of materials that do n
6、ot contain asignificant amount of fines. For example, clean sands will not yielddetectable amounts of silt and clay sized particles, and therefore shouldnot be tested with this method. The minimum amount of fines in thesedimentation specimen is 15 g.1.3 When combining the results of the sedimentatio
7、n andsieve tests, the procedure for obtaining the material for thesedimentation analysis and calculations for combining theresults will be provided by the more general test method, suchas Test Methods D6913 (Note 2).NOTE 2Subcommittee D18.03 is currently developing a new testmethod “Test Method for
8、Particle-Size Analysis of Soils Combining theSieve and Sedimentation Techniques.”1.4 The terms “soil” and “material” are used interchange-ably throughout the standard.1.5 The sedimentation analysis is based on the concept thatlarger particles will fall through a fluid faster than smallerparticles. S
9、tokes Law gives a governing equation used todetermine the terminal velocity of a spherical particle fallingthrough a stationary liquid. The terminal velocity is propor-tional to the square of the particle diameter.Therefore, particlesare sorted by size in both time and position when settling in acon
10、tainer of liquid.1.5.1 Stokes Law has several assumptions which are: theparticles are spherical and smooth; there is no interferencebetween the particles; there is no difference between thecurrent in the middle of the container and the sides; flow islaminar; and the particles have the same density.
11、Theseassumptions are applied to soil particles of various shapes andsizes.1.6 A hydrometer is used to measure the fluid density anddetermine the quantity of particles in suspension at a specifictime and position. The density of the soil-water suspensiondepends upon the concentration and specific gra
12、vity of the soilparticles and the amount of dispersant added. Each hydrometermeasurement at an elapsed time is used to calculate thepercentage of particles finer than the diameter given by StokesLaw. The series of readings provide the distribution of materialmass as a function of particle size.1.7 T
13、his test method does not cover procurement of thesample or processing of the sample prior to obtaining thereduced sample in any detail. It is assumed that the sample isobtained using appropriate methods and is representative ofsite materials or conditions. It is also assumed that the samplehas been
14、processed such that the reduced sample accuratelyreflects the particle-size distribution (gradation) of this finerfraction of the material.1.8 Material ProcessingMaterial is tested in the moist oras-received state unless the material is received in an air-driedstate. The moist preparation method sha
15、ll be used to obtain asedimentation test specimen from the reduced sample. Air-dried preparation is only allowed when the material is receivedin the air-dried state. The method to be used may be specifiedby the requesting authority; however, the moist preparationmethod shall be used for referee test
16、ing.1.9 This test method is not applicable for the followingsoils:1.9.1 Soils containing fibrous peat.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.03 on Texture, Plasticityand Density Characteristics of Soils.Cu
17、rrent edition approved May 1, 2017. Published May 2017. Originallyapproved in 2016. Last previous edition approved in 2016 as D7928 161. DOI:10.1520/D7928-17Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard wa
18、s developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.11.9.2 Soils
19、containing less than approximately 5 % of fine-grained material (Note 1).1.9.3 Soils containing extraneous matter, such as organicsolvents, oil, asphalt, wood fragments, or similar items (Note3).NOTE 3If extraneous matter, such as wood, can be easily removed byhand, it is permissible to do so. Howev
20、er, there may be cases where theextraneous matter is being evaluated as part of the material and it shouldnot be removed from the material.1.9.4 Materials that contain cementitious components, suchas cement, fly ash, lime, or other stabilization admixtures.1.10 This test method may not produce consi
21、stent testresults within and between laboratories for the following soils.To test these soils, this test method must be adapted and theseadaptations documented.1.10.1 Soils that flocculate during sedimentation. Such ma-terials may need to be treated to reduce salinity or alter the pHof the suspensio
22、n.1.10.2 Friable soils in which processing changes the grada-tion of the soil. Typical examples of these soils are someresidual soils, most weathered shales, and some weakly ce-mented soils.1.10.3 Soils that will not readily disperse, such as glauco-nitic clays or some dried plastic clays.1.11 Sampl
23、es that are not soils, but are made up of particlesmay be tested using this method. The applicable sections aboveshould be used in applying this standard.1.12 UnitsThe values stated in SI units are to be regardedas standard. Except the sieve designations, they are identifiedusing the “alternative” s
24、ystem in accordance with Practice E11,such as 3-in. and No. 200, instead of the “standard” of 75-mmand 75-m, respectively. Reporting of test results in units otherthan SI shall not be regarded as non-conformance with this testmethod. The use of balances or scales recording pounds ofmass (lbm) shall
25、not be regarded as nonconformance with thisstandard.1.13 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026, unless superseded by this test method.1.13.1 The procedures used to specify how data arecollected/recorded and
26、calculated in the standard are regardedas the industry standard. In addition, they are representative ofthe significant digits that generally should be retained. Theprocedures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider-ations for
27、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 these test methods to consider significant digits used inanalysis methods for engineering data.1.14 This standard does not pu
28、rport 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 and health practices and determine the applica-bility of regulatory limitations prior to use.1.15 This international standard was develop
29、ed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Docume
30、nts2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD854 Test Methods for Specific Gravity of Soil Solids byWater PycnometerD1140 Test Methods for Determining the Amount of Mate-rial Finer than 75-m (No. 200) Sieve in Soils by WashingD2216 Test Methods for Laboratory D
31、etermination of Water(Moisture) Content of Soil and Rock by MassD2487 Practice for Classification of Soils for EngineeringPurposes (Unified Soil Classification System)D2488 Practice for Description and Identification of Soils(Visual-Manual Procedure)D3740 Practice for Minimum Requirements for Agenci
32、esEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4220/D4220M Practices for Preserving and TransportingSoil SamplesD4318 Test Methods for Liquid Limit, Plastic Limit, andPlasticity Index of SoilsD4753 Guide for Evaluating, Selecting, and Specifying
33、 Bal-ances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingD6026 Practice for Using Significant Digits in GeotechnicalDataD6913 Test Methods for Particle-Size Distribution (Grada-tion) of Soils Using Sieve AnalysisE11 Specification for Woven Wire Test Sieve Cloth and Test
34、SievesE100 Specification for ASTM HydrometersE126 Test Method for Inspection, Calibration, and Verifica-tion of ASTM Hydrometers3. Terminology3.1 Definitions:3.1.1 For definitions of common technical terms used in thisstandard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Stan
35、dard:3.2.1 reduced sample, nthe minus38-in. (9.5-mm) sieveor finer material that has been separated from the sample andthen worked to reduce the mass while still having sufficientquantity to meet the minimum mass requirements of Table 1.3.2.2 sample, nmaterial collected without limitation onthe tota
36、l mass or size range of particles meeting the minimummass requirements provided in Table 1.3.2.3 sedimentation sample, nthe minus No. 10 (2.0-mm)or finer material that is separated from the reduced sample2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Se
37、rvice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.D7928 172using the separation sieve from which the sedimentationspecimen and water content are obtained.3.2.4 sedimentation specimen, nthe material obtainedf
38、rom the sedimentation sample having a maximum particle-size no greater than the No. 10 (2.0-mm) sieve to be used in thesedimentation test and in sufficient quantity to satisfy theminimum mass requirements of Table 1.3.2.5 separation sieve, nthe No. 10 (2.0-mm) sieve orfiner (Note 4) used to separate
39、 the reduced sample to obtain thematerial for the sedimentation sample.NOTE 4The methodology for using a sieve finer than the No. 10 (2.0mm) is not defined in this standard. The methodology used to obtain arepresentative sample using a sieve finer than the No. 10 (2.0 mm) is notthe same as obtaining
40、 the representative sample using the No. 10 (2.0 mm)sieve as presented in this standard.Additional effort or steps are necessaryto make sure the material passing the finer sieve adequately represents thesample. Such additional effort or steps should be documented if using asieve finer than the No. 1
41、0 (2.0 mm) sieve to obtain the sedimentationspecimen.4. Summary of Test Method4.1 This test method is used to determine the particle-sizedistribution (gradation) of material finer than the No. 200(75-m) sieve as a percentage of the mass used in thesedimentation test.4.2 When the source material cont
42、ains particles larger thanthe38-in. (9.5-mm) sieve, a reduced sample passing the38-in.(9.5-mm) sieve shall be obtained using techniques presented inTest Methods D6913 or another standard. This reduced sampleshall meet the minimum mass requirements in Table 1 for the38-in. (9.5-mm) sieve. The materia
43、l is processed using themoist (referee) preparation method unless the material isreceived in the air-dried state.4.3 The entire reduced sample is separated using the sepa-ration sieve. The sedimentation sample is then split to obtainthe appropriate mass for the sedimentation test specimen and awater
44、 content test specimen.4.4 The sedimentation test specimen is mixed with a dis-persing agent and test water. The slurry is allowed to conditionand is then thoroughly mixed and placed in a cylinder withadditional test water. Readings are taken with a hydrometer andthermometer over specific time inter
45、vals.4.5 The mass of particles passing specified particle diam-eters are calculated and recorded. The results produce atabulation of particle size versus percent passing that can begraphically presented as a gradation curve. The plot is typicallyexpressed as percent passing/finer than the separation
46、 sievesize versus the log of the particle size in millimetres.5. Significance and Use5.1 Particle-size distribution (gradation) is a descriptiveterm referring to the proportions by dry mass of a soildistributed over specified particle-size ranges. The gradationcurve generated using this method yield
47、s the amount of silt andclay size fractions present in the soil based on size definitions,not mineralogy or Atterberg limit data.5.2 Determination of the clay size fraction, which is mate-rial finer than 2 m, is used in combination with the PlasticityIndex (Test Methods D4318) to compute the activit
48、y, whichprovides an indication of the mineralogy of the clay fraction.5.3 The gradation of the silt and clay size fractions is animportant factor in determining the susceptibility of fine-grained soils to frost action.5.4 The gradation of a soil is an indicator of engineeringproperties. Hydraulic co
49、nductivity, compressibility, and shearstrength are related to the gradation of the soil. However,engineering behavior is dependent upon many factors, such aseffective stress, mineral type, structure, plasticity, and geologi-cal origin, and cannot be based solely upon gradation.5.5 Some types of soil require special treatment in order tocorrectly determine the particle sizes. For example, chemicalcementing agents can bond clay particles together and shouldbe treated in an effort to remove the cementing agents whenpossible. Hydrogen peroxide and mod
