1、Designation: D6572 13Standard Test Methods forDetermining Dispersive Characteristics of Clayey Soils bythe Crumb Test1This standard is issued under the fixed designation D6572; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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. Scope*1.1 Two test methods are provided to give a qualitativeindication of the natural dispersive characteristics of clay
3、eysoils:. Method A and Method B.1.1.1 Method AProcedure for Natural Soil Crumbs de-scribed in 10.2.1.1.2 Method BProcedure for Remolded Soil Crumbsdescribed in 10.3.1.2 The crumb test, while a good, quick indication ofdispersive soil, should usually be run in conjunction with apinhole test and a dou
4、ble hydrometer test, Test Methods A6and A5, respectively.1.3 The crumb test has some limitations in its usefulness asan indicator of dispersive soil.Adispersive soil may sometimesgive a non-dispersive reaction in the crumb test. Soils contain-ing kaolinite with known field dispersion problems, haves
5、hown non-dispersive reactions in the crumb test (1).2However, if the crumb test indicates dispersion, the soil isprobably dispersive.1.4 These test methods are not applicable for soils with 12% or less of the particles passing 0.005 mm and having aplasticity index less than or equal to 8, as determi
6、ned by TestMethod A9.1.5 Oven-dried soil should not be used to prepare crumb testspecimens, as irreversible changes could occur to the soilpore-water physicochemical properties responsible for disper-sion (2).NOTE 1In some cases, the results of the pinhole, crumb, anddouble-hydrometer test methods m
7、ay disagree. The crumb test is a betterindicator of dispersive soils than of non-dispersive soils (3).1.6 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.6.1 The procedures used to specify how data are collected/rec
8、orded or calculated in this standard are regarded as theindustry standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider
9、-ations for 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 this standard to consider significant digits used in analyticalmethods for engineering design.1.7 The values stat
10、ed in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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 standard to establish appro-priate safety and
11、 health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D653 Terminology Relating to Soil, Rock, and ContainedFluidsD1193 Specification for Reagent WaterD2216 Test Methods for Laboratory Determination of Water(Moisture) Con
12、tent of Soil and Rock by MassD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4221 Test Method for Dispersive Characteristics of ClaySoil by Double HydrometerD4318 Test Methods for Liquid Limit, Pl
13、astic Limit, andPlasticity Index of SoilsD4647 Test Method for Identification and Classification ofDispersive Clay Soils by the Pinhole TestD6026 Practice for Using Significant Digits in GeotechnicalData1These test methods are under the jurisdiction of ASTM Committee D18 on Soiland Rock and are the
14、direct responsibility of Subcommittee D18.06 on Physical-Chemical Interactions of Soil and RockCurrent edition approved Nov. 1, 2013. Published November 2013. Originallyapproved in 2006. Last previous edition approved in 2012 as D4186 12. DOI:10.1520/D6572-13.2The boldface numbers in parentheses ref
15、er to the list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Su
16、mmary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E1 Specification for ASTM Liquid-in-Glass ThermometersE11 Specification for Woven Wire Test Sieve Cloth and TestSievesE2251 Sp
17、ecification for Liquid-in-Glass ASTM Thermom-eters with Low-Hazard Precision Liquids3. Terminology3.1 Definitions:3.1.1 For definitions of common technical terms in thisstandard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 dispersive claysa type of soil that di
18、saggregateseasily and rapidly, without significant mechanical assistance, inwater of low-salt concentration.3.2.1.1 DiscussionSuch soils usually have a high propor-tion of their adsorptive capacity saturated with sodium cationsalthough adsorbed lithium and magnesium may also play a role(4). Such soi
19、ls also generally have a high shrink-swellpotential, have low resistance to erosion, and have lowpermeability in an intact state.4. Summary of Test Method4.1 Acube of remolded soil with approximately 15 6 5mmon each side (about the size of a single die in a pair of dice) ora natural soil crumb of ap
20、proximately similar volume is placedon the bottom of a 300-mL container containing 250 mL ofType IV water.4.2 The temperature of the water is recorded and visualdeterminations of the dispersion grade are made and recordedat 2 min 6 15 s, 1 h 6 8 min, and 6 h 6 45 min. Determinationof grade is based
21、on the formation, extent, and turbidity of adense “cloud” or halo of colloidal-sized particles extendingfrom the soil crumb.4.3 Determinations consist of: Grade 1 (Non-dispersive),Grade 2 (Intermediate), Grade 3 (Dispersive), and Grade 4(Highly Dispersive).5. Significance and Use5.1 The crumb test p
22、rovides a simple, quick method for fieldor laboratory identification of a dispersive clayey soil. Theinternal erosion failures of a number of homogeneous earthdams, erosion along channel or canal banks, and rainfallerosion of earthen structures have been attributed to colloidalerosion along cracks o
23、r other flow channels formed in massesof dispersive clay (5).5.2 The crumb test, as originally developed by Emerson (6),was called the aggregate coherence test and had seven differentcategories of soil-water reactions. Sherard (5) later simplifiedthe test by combining some soil-water reactions so th
24、at onlyfour categories, or grades, of soil dispersion are observedduring the test. The crumb test is a relatively accurate positiveindicator of the presence of dispersive properties in a soil. Thecrumb test, however, is not a completely reliable negativeindicator that soils are not dispersive. The c
25、rumb test canseldom be relied upon as a sole test method for determining thepresence of dispersive clays. The double-hydrometer test (TestMethod D4221) and pinhole test (Test Method D4647) are testmethods that provide valuable additional insight into theprobable dispersive behavior of clay soils.NOT
26、E 2The quality of the result produced by these test methods isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing. User
27、s of these test methods are cautioned thatcompliance with Practice D3740 does not in itself ensure reliable testing.Reliable testing depends on several factors; Practice D3740 provides ameans of evaluating some of those factors.6. Interference6.1 Oven-dried soil shall not be used in performing thecr
28、umb test as irreversible changes could occur to the soilpore-water physicochemical properties responsible for disper-sion (2).6.2 The use of water other than Type IV in accordance withSpecification D1193, can interfere with dispersion of thecolloidal clay particles.6.3 The cube or crumb shall be car
29、efully placed directly onthe bottom of the dish when submerging the crumb. Droppingthe crumb from the water surface can cause excessive slakingand may result in erroneous interpretation of the dispersiongrade.6.4 Jarring or moving the soil specimen or container oncethe test method has begun can caus
30、e excessive turbidity andmay result in erroneous interpretation of the dispersion grade.6.5 The use of a single, natural, irregular-shaped soil crumbmay result in a specimen that is not representative of the totalsample. Therefore, several crumb test specimens should beselected to make sure that rep
31、resentative test results areobtained. The total number of test specimens should bedetermined during the test program and will depend on thedegree of agreement of individual test results.6.6 These test methods are not applicable to soils with 12 %or less of the particles passing 0.005 mm and having a
32、plasticity index less than or equal to 8, as determined by TestMethod D4318.7. Apparatus7.1 Specimen ContainerA white or clear, non-porous,glass or equivalent inert container with a minimum capacity of300 mL and having a flat bottom of at least 85-mm across. Thecontainer shall be large enough to all
33、ow for the specimen to befully immersed when placed in the container.7.2 Thermometer0 to 50C range, 0.1C divisions, con-forming to the requirements of Specification E1. Temperaturemeasuring devices such as RTDs, thermistors, or liquid-in-glass thermometers (for example, Specification E2251) con-form
34、ing to Specification E1, and the temperature range andaccuracy may be used.7.3 Sieve(s), 4.75-mm (No. 4) and 2-mm (No. 10) sieve, inaccordance with Specification E11.7.4 Timing DeviceA clock, stopwatch, digital timer, oralike readable to 1 second or better.D6572 1328. Reagents and Materials8.1 Purit
35、y of WaterType IV water in accordance withSpecification D1193 or distilled water with a pH between 5.5and 7.0 should be used for conducting the test methods andpreparing remolded specimens. Distilled water is preferred.9. Sampling9.1 SamplingObtain a representative, homogenous soilsample passing the
36、 4.75-mm (No. 4) sieve. Depending on thepercentage of coarse sand in the material, approximately 25 to75 g of material is needed to perform a crumb test. If usingMethod A, more material may be needed in order to make surerepresentative test results are obtained. Material for the crumbtest should be
37、selected as soon as possible after obtaining therepresentative sample as discussed in 10.1.9.1.1 Determine the water content of the sample prior tospecimen(s) preparation according to Test Method D2216 andrecord to the nearest 0.1 %. Record the qualitative state used inthe determination such as, in
38、situ, as-received or air-dried.10. Test Specimen(s)10.1 Preserve the test specimen(s) at the in situ or as-received water content, if possible, or allowed to air-dry. Donot oven dry the test specimen(s).10.2 Method ANatural Soil Crumbs:10.2.1 Select one or more natural, irregularly shaped, soilcrumb
39、s from the sample obtained in Section 9 with anabundance of aggregated soil lumps suitable for crumb testspecimens. This soil crumb should be approximately the samevolume as a cube with 15 6 5 mm on each side (about the sizeof a single die of a pair of dice). If no one crumb is equivalentto this siz
40、e cube, a series of smaller cubes can be used. Thecrumb volume should not be less than equivalent to a cube with7 6 3 mm on each side. Record the test specimen identificationinformation and begin the test as soon as practicable afterobtaining the test specimen(s).10.2.2 Use of natural soil crumbs ma
41、y result in a specimenthat is not representative of the total sample; therefore, it isrecommended that several crumb specimens be tested to makesure the total sample is represented. The number chosen isdependent on the homogeneity of the total sample.10.3 Test Method BRemolded Soil Crumbs:10.3.1 Pro
42、cess the sample over a 2-mm (No. 10) sieve andretain the material passing the 2-mm (No. 10) sieve.10.3.2 Prepare a test specimen from the material passing the2-mm (No. 10) sieve by lightly compressing a moist soilsample into a cube approximately 15 6 5 mm on each side.Use the thumbs and index finger
43、 to gently form the cube.Record the test specimen identification information and beginthe test as soon as practicable after obtaining the test speci-men(s).10.4 If the crumb test is performed in conjunction with thepinhole test (Test Method D4647), the cube can be preparedfrom material cured to the
44、moisture content desired forcompacting the pinhole specimen. Alternatively, air-dried soilor soil at the natural moisture can be passed through a 2-mm(No. 10) sieve and formed into the cube. If additional moistureis needed to form the cube, Type IV or distilled water can beadded until the cube can b
45、e formed.11. Procedure11.1 For either Method, place the specimen container de-scribed in 7.1 on a horizontal working surface, which will berelatively free of vibration for the next 6 h 6 45 min.11.2 Pour approximately 250-mL of Type IV or distilledwater into the container and allow the water tempera
46、ture toequalize to 21 6 6C. This temperature shall be maintainedthroughout the test.11.3 Verify the water temperature has equalized prior toplacing the specimen in the water. Record the temperature tothe nearest 0.1C.11.4 Record the specimen container identification alongwith the test specimen that
47、is placed in that container.NOTE 3Placing the container(s) on the top edge of the test formfacilitates easy identification of a number of specimens and reduces thepotential for misidentification.11.5 Carefully place the specimen in the water and gentlyrelease it only after placing it directly on the
48、 bottom of thecontainer . Do not move or vibrate the container or stir thewater from specimen placement until the end of this test.11.6 Record the time of specimen placement and start thetiming device.11.7 As the soil crumb begins to absorb water, observe thetendency for colloidal-sized particles to
49、 deflocculate and gointo suspension.NOTE 4The colloidal-sized particles are visible in the form of a dense“cloud” or halo that extends from the soil crumb. The extent and turbidityof the suspended clay particle “cloud” is visually interpreted. The colloidal“cloud” is influenced by soil color; that is, dark soils produce a darker,more distinctly visible “cloud.”11.8 Determine and record the dispersion grade, in accor-dance with the following criteria (Fig. 1), and temperature at 2min 6 15 s, 1 hour 6 8 min, and 6 hours 6 45 min. Be carefulto submerge the thermomet
