ASTM D425-88(2001)
(Test Method)Standard Test Method for Centrifuge Moisture Equivalent of Soils
Standard Test Method for Centrifuge Moisture Equivalent of Soils
SIGNIFICANCE AND USE
Not all water contained in a saturated soil can be removed by gravity drainage. The amount of water retained after gravity drainage is usually expressed as water holding capacity or specific retention. It varies with time, and with the particle-size distribution and plasticity of the soil (in general, increasing in value with increasing plasticity index).
In general, the centrifuge moisture equivalent is based on the theory of applying a centrifugal force great enough to reduce the capillary fringe zone enough that it can be ignored without introducing much error, even in small specimens, and yet not so great as to withdraw a large proportion of the water that is held securely above the capillary fringe. For example, if a soil will hold water 100 mm by capillarity acting against gravity, the soil will theoretically be able to hold the water only 0.1 mm against a centrifugal force that is 1000 times greater than the force of gravity. It has been determined that for at least medium-textured soils (sandy to silty particle-size distribution) the centrifuge moisture equivalent approximates the water holding capacity and when combined with the bulk density can be used to calculate an approximate specific retention and specific yield. These properties when combined with porosity can be used to estimate aquifer storage coefficient.
SCOPE
1.1 This test method covers the determination of the moisture equivalent of soil in the laboratory by means of a centrifuge technique.
1.2 This test method is limited to disturbed specimens of coarse-grained soils having fines of low plasticity such as SP, SW, SC-SM, or SM soils. The test is limited to soils passing the 2.00-mm sieve or that fraction of a soil passing a 2.00-mm sieve.
Note 1—Test Method D 3152 or Test Method D 2325 should be used to evaluate the capillary-moisture relations of fine-grained soils and coarse-grained soils having fines of medium to high plasticity, undisturbed soils, and soils at specific desired units weights.
1.3 The test method is temperature-dependent, and consistent comparable results can be obtained only if the tests are performed under a constant-temperature condition.
1.4 The values stated in SI units are to be regarded as the standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D425–88(Reapproved 2001)
Standard Test Method for
Centrifuge Moisture Equivalent of Soils
This standard is issued under the fixed designation D 425; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope Construction Materials Testing
E 11 Specification for Wire-Cloth Sieves for Testing Pur-
1.1 This test method covers the determination of the mois-
poses
ture equivalent of soil in the laboratory by means of a
centrifuge technique.
3. Terminology
1.2 This test method is limited to disturbed specimens of
3.1 All definitions are in accordance with Terminology
coarse-grained soils having fines of low plasticity such as SP,
D 653. Terms of particular significance are as follows:
SW,SC-SM,orSMsoils.Thetestislimitedtosoilspassingthe
3.2 capillary fringe zone—the zone above the free water
2.00-mm sieve or that fraction of a soil passing a 2.00-mm
elevation in which water is held by capillary action.
sieve.
3.3 centrifuge moisture equivalent—the water content of a
NOTE 1—Test Method D 3152 or Test Method D 2325 should be used
soilafterithasbeensaturatedwithwaterandthensubjectedfor
to evaluate the capillary-moisture relations of fine-grained soils and
one hour to a centrifugal force equal to 1000 times that of
coarse-grainedsoilshavingfinesofmediumtohighplasticity,undisturbed
gravity.
soils, and soils at specific desired units weights.
3.4 specific retention—the ratio of the volume of water that
1.3 The test method is temperature-dependent, and consis-
cannot be drained from a saturated soil under the action of
tent comparable results can be obtained only if the tests are
force of gravity to the total volume of voids.
performed under a constant-temperature condition.
3.5 water-holding capacity—thesmallestvaluetowhichthe
1.4 The values stated in SI units are to be regarded as the
water content of soil or rock can be reduced by gravity
standard.
drainage.
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
4.1 The centrifuge moisture equivalent of soils is deter-
priate safety and health practices and determine the applica-
mined by initially air-drying the soil, selecting two 5-g test
bility of regulatory limitations prior to use.
specimens, thoroughly soaking each test specimen, and then
determining the water content of each specimen after it has
2. Referenced Documents
been centrifuged for 1 h at a force equal to 1000 times that of
2.1 ASTM Standards:
gravity at a controlled temperature of 20 6 1°C.
D 653 Terminology Relating to Soil, Rock, and Contained
Fluids
5. Significance and Use
D 2216 TestMethodforLaboratoryDeterminationofWater
5.1 Not all water contained in a saturated soil can be
(Moisture) Content of Soil and Rock by Mass
removed by gravity drainage. The amount of water retained
D 2325 Test Method for Capillary-Moisture Relationships
after gravity drainage is usually expressed as water holding
for Coarse- and Medium-Textured Soils by Porous-Plate
capacity or specific retention. It varies with time, and with the
Apparatus
particle-size distribution and plasticity of the soil (in general,
D 3152 Test Method for Capillary-Moisture Relationships
increasing in value with increasing plasticity index).
for Fine-Textured Soils by Pressure-MembraneApparatus
5.2 In general, the centrifuge moisture equivalent is based
D 4753 Specification for Evaluating, Selecting, and Speci-
on the theory of applying a centrifugal force great enough to
fying Balances and Scales for Use in Soil, Rock, and
reduce the capillary fringe zone enough that it can be ignored
without introducing much error, even in small specimens, and
yet not so great as to withdraw a large proportion of the water
that is held securely above the capillary fringe. For example, if
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.03 onTexture, Plasticity,
a soil will hold water 100 mm by capillarity acting against
and Density Characteristics of Soils.
Current edition approved May 27, 1988. Published July 1988. Originally
e1
published as D 425 – 35 T. Last previous edition D 425 – 79 .
2 3
Annual Book of ASTM Standards, Vol 04.08. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D425
gravity,thesoilwilltheoreticallybeabletoholdthewateronly For normal equipment installation, N will equal approxi-
0.1 mm against a centrifugal force that is 1000 times greater mately 2300 rpm.
thantheforceofgravity.Ithasbeendeterminedthatforatleast
6.2 Gooch Crucible—A procelain Gooch crucible having a
medium-textured soils (sandy to silty particle-size distribution)
perforated bottom, a capacity of approximately 25 mL, and a
the centrifuge moisture equivalent approximates the water
diameter at bottom of about 20 mm (Fig. 1). Crucibles should
holding capacity and when combined with the bulk density can
be numbered and paired in such a way that their masses meet
be used to calculate an approximate specific retention and
the requirements of the manufacturer of the centrifuge.
specific yield. These properties when combined with porosity
6.3 Babcock Trunnion Cups—Atleastonepairofcentrifuge
can be used to estimate aquifer storage coefficient.
cups with caps and with a crucible holder for supporting the
Gooch crucible above the bottom of the cup (Fig. 1). The
6. Apparatus
holder shall have sufficient clearance to fit fully within the cup
6.1 Centrifuge—A centrifuge of such a size and so driven
and short support the cup in such a manner that the water
that a force equal to 1000 times the force of gravity may be
ejected during the centrifuging operation does not come in
exerted on the center of gravity of the soil specimen for 1 h.
contact with the crucible and soil. Cups and crucible holders
The centrifuge chamber shall be capable of maintaining a
should be balanced in pairs opposite each other in the centri-
controlled temperature of 20 6 1°C. The revolutions per
fuge and should be numbered in pairs (for example, 1, 1A, 2,
minute, N,requiredtoprovideacentrifugalforceof1000times
2A, etc.).
gravity is determined from the equation:
6.4 Filter Paper—A circular piece of filter paper just large
RCF
enough to cover the inside bottom of the Gooch crucible.
N 5
Œ
0.0000111 rm
(1)
NOTE 2—Filter papers may be purchased already cut to size from a
scientific supply company.Amedi
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.