1、Designation: D 425 88 (Reapproved 2008)Standard Test Method forCentrifuge Moisture Equivalent of Soils1This standard is issued under the fixed designation D 425; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. 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 mois-ture equivalent of soil in the laboratory by means of acentrifuge techni
3、que.1.2 This test method is limited to disturbed specimens ofcoarse-grained soils having fines of low plasticity such as SP,SW, SC-SM, or SM soils. The test is limited to soils passing the2.00-mm sieve or that fraction of a soil passing a 2.00-mmsieve.NOTE 1Test Method D 3152 or Test Method D 2325 s
4、hould be usedto evaluate the capillary-moisture relations of fine-grained soils andcoarse-grained soils having fines of medium to high plasticity, undisturbedsoils, and soils at specific desired units weights.1.3 The test method is temperature-dependent, and consis-tent comparable results can be obt
5、ained only if the tests areperformed under a constant-temperature condition.1.4 The values stated in SI units are to be regarded as thestandard.1.5 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 standa
6、rd 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:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 2216 Test Methods for Laboratory Determination of Wa-ter (Moistur
7、e) Content of Soil and Rock by MassD 2325 Test Method for Capillary-Moisture Relationshipsfor Coarse- and Medium-Textured Soils by Porous-PlateApparatus3D 3152 Test Method for Capillary-Moisture Relationshipsfor Fine-Textured Soils by Pressure-MembraneApparatus3D 4753 Guide for Evaluating, Selecting
8、, and SpecifyingBalances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingE11 Specification for Wire Cloth and Sieves for TestingPurposes3. Terminology3.1 All definitions are in accordance with TerminologyD 653. Terms of particular significance are as follows:3.2 capillary
9、 fringe zonethe zone above the free waterelevation in which water is held by capillary action.3.3 centrifuge moisture equivalentthe water content of asoil after it has been saturated with water and then subjected forone hour to a centrifugal force equal to 1000 times that ofgravity.3.4 specific rete
10、ntionthe ratio of the volume of water thatcannot be drained from a saturated soil under the action offorce of gravity to the total volume of voids.3.5 water-holding capacitythe smallest value to which thewater content of soil or rock can be reduced by gravitydrainage.4. Summary of Test Method4.1 The
11、 centrifuge moisture equivalent of soils is deter-mined by initially air-drying the soil, selecting two 5-g testspecimens, thoroughly soaking each test specimen, and thendetermining the water content of each specimen after it hasbeen centrifuged for 1 h at a force equal to 1000 times that ofgravity
12、at a controlled temperature of 20 6 1C.5. Significance and Use5.1 Not all water contained in a saturated soil can beremoved by gravity drainage. The amount of water retainedafter gravity drainage is usually expressed as water holdingcapacity or specific retention. It varies with time, and with thepa
13、rticle-size distribution and plasticity of the soil (in general,increasing in value with increasing plasticity index).5.2 In general, the centrifuge moisture equivalent is basedon the theory of applying a centrifugal force great enough toreduce the capillary fringe zone enough that it can be ignored
14、without introducing much error, even in small specimens, andyet not so great as to withdraw a large proportion of the water1This 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 Charac
15、teristics of Soils.Current edition approved Feb. 1, 2008. Published March 2008. Originallyapproved in 1935. Last previous edition approved in 2001 as D 425 88 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual B
16、ook of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.that is held securely above the capillary fringe. For example, ifa so
17、il will hold water 100 mm by capillarity acting againstgravity, the soil will theoretically be able to hold the water only0.1 mm against a centrifugal force that is 1000 times greaterthan the force of gravity. It has been determined that for at leastmedium-textured soils (sandy to silty particle-siz
18、e distribution)the centrifuge moisture equivalent approximates the waterholding capacity and when combined with the bulk density canbe used to calculate an approximate specific retention andspecific yield. These properties when combined with porositycan be used to estimate aquifer storage coefficien
19、t.6. Apparatus6.1 CentrifugeA centrifuge of such a size and so driventhat a force equal to 1000 times the force of gravity may beexerted on the center of gravity of the soil specimen for 1 h.The centrifuge chamber shall be capable of maintaining acontrolled temperature of 20 6 1C. The revolutions pe
20、rminute, N, required to provide a centrifugal force of 1000 timesgravity is determined from the equation:N 5RCF0.0000111 rm(1)where:N = revolutions per minute,RCF = relative centrifugal force (1000),r = radius of rotation to center of gravity of the testspecimen, cm, andm = mass of the body, taken a
21、s unity.For normal equipment installation, N will equal approxi-mately 2300 rpm.6.2 Gooch CrucibleA procelain Gooch crucible having aperforated bottom, a capacity of approximately 25 mL, and adiameter at bottom of about 20 mm (Fig. 1). Crucibles shouldbe numbered and paired in such a way that their
22、masses meetthe requirements of the manufacturer of the centrifuge.6.3 Babcock Trunnion CupsAt least one pair of centrifugecups with caps and with a crucible holder for supporting theGooch crucible above the bottom of the cup (Fig. 1). Theholder shall have sufficient clearance to fit fully within the
23、 cupand short support the cup in such a manner that the waterejected during the centrifuging operation does not come incontact with the crucible and soil. Cups and crucible holdersshould be balanced in pairs opposite each other in the centri-fuge and should be numbered in pairs (for example, 1, 1A,
24、2,2A, etc.).FIG. 1 Crucible, Trunnion Cup, and Cup HolderD 425 88 (2008)26.4 Filter PaperA circular piece of filter paper just largeenough to cover the inside bottom of the Gooch crucible.NOTE 2Filter papers may be purchased already cut to size from ascientific supply company. A medium speed, high w
25、et strength (hardened)paper is recommended.6.5 BalanceA balance having a readability of 0.01 g, andaccurate to 60.03 g.NOTE 3For additional information on balances refer to SpecificationD 4753.6.6 HumidifierA desiccator cabinet or large desiccator jarwith water in the lower half works satisfactorily
26、. The desiccatorplate should be covered with hardware cloth on which to set thecrucibles and soil specimens.6.7 OvenA thermostatically controlled drying oven, pref-erably of the forced-draft type, capable of maintaining auniform temperature of 110 6 5C throughout.6.8 Water Content ContainersSuitable
27、 containers made ofmaterial resistant to corrosion and change in mass uponrepeated heating, cooling, and cleaning. Containers shall haveclose-fitting lids to prevent loss of moisture from the soilbefore initial weighing and to prevent absorption of moisturefrom the atmosphere following oven drying a
28、nd before finalweighing. One container is needed for each water contentdetermination. Containers should be 60 to 90-mL capacity.NOTE 4It is recommended that the containers be numbered in pairs tocoincide with the crucible numbers.6.9 Mortar and PestleA mortar and rubber-covered pestlesuitable for br
29、eaking up the aggregations of soil particles.6.10 Sieve2.00-mm (No. 10) sieve conforming to Speci-fication E11. A sieve bottom pan and lid are also highlydesirable for facilitating specimen preparation.7. Test Specimen7.1 Expose the soil sample, as received, to the air at roomtemperature until dried
30、 thoroughly. Break up the aggregationsthoroughly in the mortar with a rubber-covered pestle. Drysieve this material on a 2.00-mm sieve.NOTE 5If the sample, as received, has a mass much greater thanrequired to perform this test, the sample can be thoroughly mixed and asample weighing about 50 g split
31、 out for air drying.7.2 Take two 5-g specimens from the material passing the2.00-mm sieve after it has been thoroughly mixed. Thecrucibles should be numbered and paired in such a way that themasses of the crucibles and contents meet the requirements ofthe manufacturer of the centrifuge.8. Procedure8
32、.1 Place the specimens loosely but evenly in the pairedGooch crucibles, in which previously has been placed a pieceof wet filter paper that just covers the bottom of each crucible.Place the crucible in a pan of distilled or demineralized waterof a depth at least 5 mm greater than the height of soil
33、in thecup and allow the soil to take up water until “saturated.” Eighthours or overnight usually is satisfactory, as indicated by thepresence of free water covering the surface of the soil. Placethe crucible and specimen in the humidifier to drain for at least12 h to ensure uniform distribution of m
34、oisture throughout thesoil mass. Pour or siphon off any water standing above thesurface of the specimens and place the crucibles in thecentrifuge cups fitted as described in 6.2. Place the pairedcrucibles in the centrifuge cups opposite each other in thecentrifuge.8.2 Control the centrifuge at a tem
35、perature 20 6 1C. Bringthe centrifuge to the required speed within 5 min by fivesuccessive equal steps of the rheostat, with 1 min at each step.Maintain the centrifuge for 60 min at a constant speed which,for the diameter head used, will exert a centrifugal force 1000times the force of gravity upon
36、the center of gravity of the testspecimen. Following this period of centrifuging at requiredspeed, allow the centrifuge to come to rest with as little brakingas possible, but not to exceed a 5-min time interval.8.3 When water is observed on the top of the soil aftercentrifuging, the soil is said to
37、have water-logged. The centri-fuge moisture equivalent is not considered to be valid for thismaterial and the report should be so noted.8.4 Immediately after centrifuging, transfer soil from thecrucibles to the water content containers as quickly as possibleto minimize moisture loss; it is not neces
38、sary to remove all ofthe soil from the crucibles. Then determine the water content ofeach specimen in accordance with Method D 2216.8.5 A copy of a sample data sheet is shown in Fig. 2. Anydata sheet can be used, provided the form contains all therequired data.9. Calculation9.1 Calculate the centrif
39、uge moisture equivalent as theaverage of the water contents of the two specimens.10. Report10.1 The report shall include the following:10.1.1 Identification of sample (material) being tested, byboring number, sample number, test number, etc.10.1.2 Average centrifuge moisture equivalent of the speci-
40、men to the nearest 1 %. If the specimen was water-logged, thereport should state that the centrifuge moisture equivalent wasnot valid for the soil tested.10.1.3 Indication of which test specimen, if any, was water-logged.11. Precision and Bias11.1 PrecisionInformation on the precision of this testme
41、thod is being gathered.412. Keywords12.1 centrifuge moisture equivalent; specific retention; spe-cific yield, storage capacity; water holding capacity4For a discussion of variables which affect the results of this test, see Johnson,A. I., Prill, R. C., and Morris, D. A., “Specific YieldColumn Draina
42、ge andCentrifuge Moisture Content,” U.S. Geological Survey Water Supply Paper 1662-A,1963.D 425 88 (2008)3ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised tha
43、t determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reappro
44、ved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you fe
45、el that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).FIG. 2 Centrifuge Moisture Equivalent Sample Data SheetD 425 88 (2008)4
