1、Designation: D7928 161D7928 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 ad
2、option or, 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 NOTEEditorially corrected A1.4.3.1, Fig. X1.5, and Fig. X1.6 in January 2017.1.
3、Scope1.1 This test method covers the quantitative determination of the distribution of particle sizes of the fine-grained portion of soils.The sedimentation or hydrometer method is used to determine the particle-size distribution (gradation) of the material that is finerthan the No. 200 (75-m) sieve
4、 and larger than about 0.2-m. The test is performed on material passing the No. 10 (2.0-mm) orfiner sieve and the results are presented as the mass percent finer versus the log of the particle diameter.1.2 This method can be used to evaluate the fine-grained fraction of a soil with a wide range of p
5、article sizes by combining thesedimentation results with a sieve analysis resulting in the complete gradation curve. The method can also be used when there areno coarse-grained particles or when the gradation of the coarse-grained material is not required or not needed.NOTE 1The significant digits r
6、ecorded in this test method preclude obtaining the grain size distribution of materials that do not contain a significantamount of fines. For example, clean sands will not yield detectable amounts of silt and clay sized particles, and therefore should not be tested with thismethod. The minimum amoun
7、t of fines in the sedimentation specimen is 15 g.1.3 When combining the results of the sedimentation and sieve tests, the procedure for obtaining the material for thesedimentation analysis and calculations for combining the results will be provided by the more general test method, such as TestMethod
8、s D6913 (Note 2).NOTE 2Subcommittee D18.03 is currently developing a new test method “Test Method for Particle-Size Analysis of Soils Combining the Sieve andSedimentation Techniques.”1.4 The terms “soil” and “material” are used interchangeably throughout the standard.1.5 The sedimentation analysis i
9、s based on the concept that larger particles will fall through a fluid faster than smaller particles.StokesLaw gives a governing equation used to determine the terminal velocity of a spherical particle falling through a stationaryliquid. The terminal velocity is proportional to the square of the par
10、ticle diameter. Therefore, particles are sorted by size in bothtime and position when settling in a container of liquid.1.5.1 Stokes Law has several assumptions which are: the particles are spherical and smooth; there is no interference betweenthe particles; there is no difference between the curren
11、t in the middle of the container and the sides; flow is laminar; and theparticles have the same density. These assumptions are applied to soil particles of various shapes and sizes.1.6 A hydrometer is used to measure the fluid density and determine the quantity of particles in suspension at a specif
12、ic timeand position. The density of the soil-water suspension depends upon the concentration and specific gravity of the soil particles andthe amount of dispersant added. Each hydrometer measurement at an elapsed time is used to calculate the percentage of particlesfiner than the diameter given by S
13、tokes Law. The series of readings provide the distribution of material mass as a function ofparticle size.1.7 This test method does not cover procurement of the sample or processing of the sample prior to obtaining the reducedsample in any detail. It is assumed that the sample is obtained using appr
14、opriate methods and is representative of site materialsor conditions. It is also assumed that the sample has been processed such that the reduced sample accurately reflects theparticle-size distribution (gradation) of this finer fraction of the material.1.8 Material ProcessingMaterial is tested in t
15、he moist or as-received state unless the material is received in an air-dried state.The moist preparation method shall be used to obtain a sedimentation test specimen from the reduced sample.Air-dried preparation1 This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and
16、is the direct responsibility of Subcommittee D18.03 on Texture, Plasticityand Density Characteristics of Soils.Current edition approved May 1, 2016May 1, 2017. Published May 2016May 2017. Originally approved in 2016. Last previous edition approved in 2016 as D7928 161.DOI: 10.1520/D7928-16E0110.1520
17、/D7928-17This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult
18、prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1is only allowed when the material is re
19、ceived in the air-dried state. The method to be used may be specified by the requestingauthority; however, the moist preparation method shall be used for referee testing.1.9 This test method is not applicable for the following soils:1.9.1 Soils containing fibrous peat.1.9.2 Soils containing less tha
20、n approximately 5 % of fine-grained material (Note 1).1.9.3 Soils containing extraneous matter, such as organic solvents, oil, asphalt, wood fragments, or similar items (Note 3).NOTE 3If extraneous matter, such as wood, can be easily removed by hand, it is permissible to do so. However, there may be
21、 cases where theextraneous matter is being evaluated as part of the material and it should not be removed from the material.1.9.4 Materials that contain cementitious components, such as cement, fly ash, lime, or other stabilization admixtures.1.10 This test method may not produce consistent test res
22、ults within and between laboratories for the following soils. To testthese soils, this test method must be adapted and these adaptations documented.1.10.1 Soils that flocculate during sedimentation. Such materials may need to be treated to reduce salinity or alter the pH of thesuspension.1.10.2 Fria
23、ble soils in which processing changes the gradation of the soil. Typical examples of these soils are some residualsoils, most weathered shales, and some weakly cemented soils.1.10.3 Soils that will not readily disperse, such as glauconitic clays or some dried plastic clays.1.11 Samples that are not
24、soils, but are made up of particles may 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 regarded as standard. Except the sieve designations, they are identified usingthe “alternative” system in accor
25、dance with Practice E11, such as 3-in. and No. 200, instead of the “standard” of 75-mm and 75-m,respectively. Reporting of test results in units other than SI shall not be regarded as non-conformance with this test method. Theuse of balances or scales recording pounds of mass (lbm) shall not be rega
26、rded as nonconformance with this standard.1.13 All observed and calculated values shall conform to the guidelines for significant digits and rounding established inPractice D6026, unless superseded by this test method.1.13.1 The procedures used to specify how data are collected/recorded and calculat
27、ed in the standard are regarded as theindustry standard. In addition, they are representative of the significant digits that generally should be retained. The proceduresused do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the use
28、rsobjectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with theseconsiderations. It is beyond the scope of these test methods to consider significant digits used in analysis methods for engineeringdata.1.14 This standard does not purport
29、to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.1.15 This international standard was developed in ac
30、cordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM
31、 Standards:2C702 Practice for Reducing Samples of Aggregate to Testing SizeD653 Terminology Relating to Soil, Rock, and Contained FluidsD854 Test Methods for Specific Gravity of Soil Solids by Water PycnometerD1140 Test Methods for Determining the Amount of Material Finer than 75-m (No. 200) Sieve i
32、n Soils by WashingD2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by MassD2487 Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)D2488 Practice for Description and Identification of Soils (Visual-Manual Proc
33、edure)D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used inEngineering Design and ConstructionD4220/D4220M Practices for Preserving and Transporting Soil SamplesD4318 Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of
34、 SoilsD4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and ConstructionMaterials TestingD6026 Practice for Using Significant Digits in Geotechnical Data2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Custome
35、r Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.D7928 172D6913 Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve AnalysisE11 Specification for Woven Wire Test Sieve Cloth an
36、d Test SievesE100 Specification for ASTM HydrometersE126 Test Method for Inspection, Calibration, and Verification of ASTM Hydrometers3. Terminology3.1 Definitions:3.1.1 For definitions of common technical terms used in this standard, refer to Terminology D653.3.2 Definitions of Terms Specific to Th
37、is Standard:3.2.1 reduced sample, nthe minus 38-in. (9.5-mm) sieve or finer material that has been separated from the sample and thenworked to reduce the mass while still having sufficient quantity to meet the minimum mass requirements of Table 1.3.2.2 sample, nmaterial collected without limitation
38、on the total mass or size range of particles meeting the minimum massrequirements 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 sample usingthe separation sieve from which the sedimentation specimen and water content a
39、re obtained.3.2.4 sedimentation specimen, nthe material obtained from the sedimentation sample having a maximum particle-size nogreater than the No. 10 (2.0-mm) sieve to be used in the sedimentation test and in sufficient quantity to satisfy the minimum massrequirements of Table 1.3.2.5 separation s
40、ieve, nthe No. 10 (2.0-mm) sieve or finer (Note 4) used to separate the reduced sample to obtain the materialfor the sedimentation sample.NOTE 4The methodology for using a sieve finer than the No. 10 (2.0 mm) is not defined in this standard. The methodology used to obtain arepresentative sample usin
41、g a sieve finer than the No. 10 (2.0 mm) is not the same as obtaining the representative sample using the No. 10 (2.0 mm) sieveas presented in this standard. Additional effort or steps are necessary to make sure the material passing the finer sieve adequately represents the sample.Such additional ef
42、fort or steps should be documented if using a sieve finer than the No. 10 (2.0 mm) sieve to obtain the sedimentation specimen.4. Summary of Test Method4.1 This test method is used to determine the particle-size distribution (gradation) of material finer than the No. 200 (75-m)sieve as a percentage o
43、f the mass used in the sedimentation test.4.2 When the source material contains particles larger than the 38-in. (9.5-mm) sieve, a reduced sample passing the 38-in.(9.5-mm) sieve shall be obtained using techniques presented inTest Methods D6913 or another standard.This reduced sample shallmeet the m
44、inimum mass requirements in Table 1 for the 38-in. (9.5-mm) sieve. The material is processed using the moist (referee)preparation method unless the material is received in the air-dried state.4.3 The entire reduced sample is separated using the separation sieve. The sedimentation sample is then spli
45、t to obtain theappropriate mass for the sedimentation test specimen and a water content test specimen.4.4 The sedimentation test specimen is mixed with a dispersing agent and test water. The slurry is allowed to condition and isthen thoroughly mixed and placed in a cylinder with additional test wate
46、r. Readings are taken with a hydrometer and thermometerover specific time intervals.4.5 The mass of particles passing specified particle diameters are calculated and recorded. The results produce a tabulation ofparticle size versus percent passing that can be graphically presented as a gradation cur
47、ve.The plot is typically expressed as percentpassing/finer than the separation sieve size versus the log of the particle size in millimetres.5. Significance and Use5.1 Particle-size distribution (gradation) is a descriptive term referring to the proportions by dry mass of a soil distributed overspec
48、ified particle-size ranges. The gradation curve generated using this method yields the amount of silt and clay size fractionspresent in the soil based on size definitions, not mineralogy or Atterberg limit data.TABLE 1 Minimum Dry Mass RequirementsMaximum Particle Size of Material (99% or more passi
49、ng) Minimum Dry Mass Comments on separating and splittingrequirements for sample reductionSieve Designation Particle Size, mm6 in. 152.4 500 kg Several separations3 in. 76.2 70 kg Several separations1 in. 25.4 3 kg At least one separation34 in. 19.1 1.3 kg Most likely one separation38 in. 9.5 165 g Separation for sedimentation analysisNo. 10 2.0 50 g Splitting onlyD7928 1735.2 Determination of the clay size fraction, which is material finer than 2 m, is used in combination with the Plasticity Index(Test Methods D4318) to compute the activity, which
