1、Designation: D4221 17D4221 18Standard Test Method forDispersive Characteristics of Clay Soil by DoubleHydrometer1This standard is issued under the fixed designation D4221; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 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. Scope*1.1 This test method provides an indication of the natural dispersive characteristics of clay soils by comparing the amo
3、unt ofparticles finer than 2-m as determined by this method compared to the amount of particles finer than 2-m as determined by TestMethod D7928(1).2 In order to do this comparison, two similar specimens must be obtained from the sample.1.2 This test method follows the procedure given in Test Method
4、 D7928 with the exception that the soil slurry is notmechanically dispersed and no dispersing agent is added.1.3 This test method is applicable only to soils where the position of the plasticity index versus liquid limit plots (Test MethodsD4318) falls on or above the “A” line (Practice D2487) and m
5、ore than 12 % of the soil fraction is finer than 2-m as determinedin accordance with Test Method D7928(2).1.4 Since this test method may not identify all dispersive clay soils, other tests such as, pinhole dispersion (Test MethodsD4647/D4647M), crumb (Test Methods D6572) (3-5) and the analysis of po
6、re water extraction (Test Methods D4542) (4-7) maybe performed individually or used together to help verify dispersion.1.5 UnitsThe values stated in SI units are to be regarded as the standard. Reporting of test results in units other than SI shallnot be regarded as nonconformance with this test met
7、hod.1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in PracticeD6026.1.6.1 The procedures used to specify how data are collected/recorded or calculated, in this standard are regarded as the industrystandard. In addition, they are
8、 representative of the significant digits that generally should be retained. The procedures used do notconsider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the users objectives;and it is common practice to increase or reduce significant digi
9、ts of reported data to be commensurate with these considerations.It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the
10、 responsibilityof the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.8 This international standard was developed in accordance with internationally recognized principles on standardiza
11、tionestablished 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 Standards:3D653 Terminology Relating to Soil, Rock, and Contained
12、 FluidsD2216 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 Procedures)1 Th
13、is test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.06 on Physical-ChemicalInteractions of Soil and Rock.Current edition approved July 1, 2017Jan. 1, 2018. Published July 2017February 2018. Originally approved in 1983.
14、Last previous edition approved in 20112017 asD422111.17. DOI: 10.1520/D4221-17.10.1520/D4221-18.2 The boldface numbers in parentheses refer to the list of references appended to this standard.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serv
15、iceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This 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.
16、Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section a
17、ppears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used inEngineering Design and Construction
18、D4220/D4220M Practices for Preserving and Transporting Soil SamplesD4318 Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of SoilsD4542 Test Methods for Pore Water Extraction and Determination of the Soluble Salt Content of Soils by RefractometerD4647/D4647M Test Methods for Identi
19、fication and Classification of Dispersive Clay Soils by the Pinhole TestD6026 Practice for Using Significant Digits in Geotechnical DataD6572 Test Methods for Determining Dispersive Characteristics of Clayey Soils by the Crumb TestD6913 Test Methods for Particle-Size Distribution (Gradation) of Soil
20、s Using Sieve AnalysisD7928 Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer)Analysis3. 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
21、 Specific to This Standard:3.2.1 dispersive clays, nsoils that deflocculate easily and rapidly without significant mechanical assistance in water of low-saltconcentration.3.2.1.1 DiscussionSuch soils usually have a high proportion of their adsorptive capacity saturated with sodium cation although ad
22、sorbed lithium andmagnesium may also play a role (6). Such soils also generally have a high shrink-swell potential, have low resistance to erosion,and have low permeability in an intact state.4. Summary of Test Method4.1 This test method is used to determine the percent dispersion of a soil. In orde
23、r to calculate the percent dispersion, two similarspecimens are obtained from a representative sample and then a sedimentation (hydrometer) analysis is performed on eachspecimen to determine the amount of particles finer than 2-m. The sedimentation analysis is performed following Test MethodD7928 fo
24、r both specimens, except that one of the specimens is de-aired and is not mechanically or chemically dispersed.4.2 The percent dispersion is calculated by dividing the percent passing the 2-m size from the de-aired, not dispersed specimenby the percent passing the 2-m size from the specimen that was
25、 dispersed and by multiplying the result by 100.5. Significance and Use5.1 Dispersive clays are those which normally deflocculate when exposed to water of low-salt concentration, the opposite ofaggregated clays that would remain flocculated in the same soil-water system (3, 4, 7). Generally, dispers
26、ive clays are highlyerosive, possibly subject to high shrink-swell potential, may have lower shear strength, and have lower permeability rates thanaggregated clays.5.2 When the percent dispersion equals 100, it indicates a completely dispersive clay-size fraction. When the percent dispersionequals 0
27、, it indicates completely nondispersive clay-size fraction.5.3 Available data (1) indicates that the test method has about 85 % reliance in predicting dispersive performance (85 % ofdispersive clays show more than 35 % dispersion).5.4 Since this test method may not identify all dispersive clays, des
28、ign decisions based solely on this test method may not beconservative. It is often run in conjunction with the crumb test (D6572) (4, 7), the pinhole test (D4647/D4647M), or the analysisof the pore water extract (D4542) (4, 7), or combination thereof, to identify possible dispersive clay behavior.NO
29、TE 1The quality of the result produced by this standard is dependent on the competence of the personal performing it, and the suitability of theequipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objectivetesting/sampling
30、/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliableresults depends on many factors; Practice D3740 provides a means of evaluating some of those factors.6. Apparatus6.1 Section 6 of Test Method D7928 describes
31、the equipment and tools needed for performing the sedimentation (hydrometer)analysis portion of this standard.6.2 ContainerAn airtight, glass or equivalent inert container with enough capacity to hold the minus No. 10 (2.0-mm)specimen(s).6.3 Filtering FlaskA 500-mL filtering flask with a rubber stop
32、per and a side tube capable of withstanding a vacuum.D4221 1826.4 Vacuum SystemA vacuum pump or water aspirator capable of producing a vacuum between 508 and 635 mm of Hg onthe vacuum gauge.7. Reagents7.1 Section 7 of Test Method D7928 describes the reagents needed for performing the mechanically an
33、d chemically dispersedsedimentation (hydrometer) analysis portion of this standard.7.2 Distilled WaterDistilled or demineralized water with a pH between 5.5 and 7 is the only permissible test fluid for use inthe sedimentation portion of the test. The use of tap water is not permitted.8. Sampling8.1
34、GeneralThis test method does not address, in any detail, procurement of the sample. It is assumed the sample is obtainedusing appropriate methods and is representative of the material under evaluation. The testing agency must preserve all samples inaccordance with Practice D4220/D4220M, Group B, exc
35、ept if the as-received sample does not meet those requirements. In whichcase, the water content of the sample does not have to be maintained. Section 9 of Test Method D6913 gives additional informationregarding sampling from different sources.8.2 Follow the steps given in 8.4 of Test Method D7928, i
36、ncluding the mass requirements given in Table 1 of that standard, toobtain the reduced sample from which the test specimens are to be obtained.9. Preparation of the Test Specimens9.1 Specimen ProcurementThis standard presents two preparation methods to obtain the sedimentation specimens: moist andai
37、r-dried. Moist and air-dried refers to the condition of the sample as it is being reduced to an appropriate particle size and mass.The test shall not be performed on oven-dried soil. The air-dried method shall only be used on samples received in the air-driedstate (Note 2). Since some fine-grained a
38、ir-dried soils aggregate, a mortar and rubber covered pestle is used to break upaggregations. Care must be taken to avoid disintegration or reduction of individual particles. Use only enough force as necessaryto break up the aggregations without destroying the individual particles. Additional guidan
39、ce for splitting materials to obtain arepresentative specimen is given in Test Method D6913, Annex A2.9.2 See 9.2 and 9.3 of Test Method D7928 for the moist and air-dried preparation methods, respectively.9.3 If the reduced sample contains particles larger than the No. 10 (2.0-mm) sieve, the soil mu
40、st be separated using a No. 10(2.0-mm) sieve. Process the entire reduced sample over the No. 10 (2.0-mm) sieve using a rubber scraper and, if needed, distilledwater to aid in working the soil through the sieve. Check that the soil retained on the sieve does not contain aggregations of finerparticles
41、. Any aggregations should be broken and passed through the sieve. It is not necessary that the separation be totallycomplete, but the soil passing the sieve must be representative. The amount of soil passing the No. 10 (2.0-mm) sieve must besufficient to obtain two specimens for sedimentation analys
42、is and one water content determination.9.4 If there is sufficient minus No. 10 (2.0-mm) soil, split or quarter this soil into at least three portions: one for the water contentdetermination and two for the sedimentation analyses. The water content specimen must contain 50 6 10 g of soil. If there is
43、insufficient minus No. 10 (2.0-mm) soil, do not obtain a water content specimen. Obtain the dry mass of the minus No. 10 (2.0-mm)soil at the end of the test as discussed in 11.12 of Test Method D7928. See Note 11 in Test Method D7928.9.5 If sufficient soil is available, immediately use one of the th
44、ree specimens for determination of the water content inaccordance with Test Methods D2216 and record the water content, wc to the nearest 0.1 %. Immediately place the other twospecimens into separate airtight containers. If the water content is to be determined at the end of the test, immediately pl
45、ace thetwo specimens in air tight containers to prevent moisture change.NOTE 2Air drying causes irreversible changes to the clay particles that cause permanent flocculations and decreases the fine fraction. (8)10. Procedure10.1 Mechanically and Chemically DispersedUse one of the specimens stored in
46、one of the containers to determine theamount of particles finer than 2-m in accordance with Test Method D7928. The stirring apparatus shall be used to disperse thespecimen.10.2 Not Mechanically or Chemically Dispersed:10.2.1 Determine and record the moist mass of soil, Mm, equivalent to 25 g of dry
47、soil, Md, using the following equation:Mm 5Md 3S11 wc100D (1)where:Mm = mass of moist soil, nearest 0.01 g,Md = mass of dry soil, nearest 0.01 g, andD4221 183wc = water content, nearest 0.1 %.10.2.2 Place approximately 125 mL of distilled water in the filtering flask.10.2.3 Using one of the specimen
48、s stored in one of the containers, take the moist mass, Mm, amount as determined in 10.2.1,and place it into the filtering flask with the distilled water.10.2.4 Place a rubber stopper into the mouth of the filtering flask and connect the flask to the vacuum pump. If the soil wasreceived in the air-d
49、ried state, it should be soaked for a minimum of 2 h before the filtering flask is connected to the vacuum pump.Under most conditions, 508 to 584 mm of Hg is sufficient to de-air the specimen.10.2.5 Start the vacuum pump and apply full vacuum. If bubbles do not appear, the vacuum is insufficient.10.2.6 At 3 min, 5 min, and 8 min after application of vacuum, swirl the flask several times in a rotating manner to assist inremoving entrapped air.10.2.7 Turn off the vacuum pump and disconnect the flask from the vacuum pump after a total evacuation time of 10 min.1
