ASTM D425-88(2008)
(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
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D425 − 88 (Reapproved 2008)
Standard Test Method for
Centrifuge Moisture Equivalent of Soils
This standard is issued under the fixed designation D425; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope Apparatus (Withdrawn 2007)
D3152 Test Method for Capillary-Moisture Relationships
1.1 This test method covers the determination of the mois-
for Fine-Textured Soils by Pressure-MembraneApparatus
ture equivalent of soil in the laboratory by means of a
(Withdrawn 2007)
centrifuge technique.
D4753 Guide for Evaluating, Selecting, and Specifying Bal-
1.2 This test method is limited to disturbed specimens of
ances and Standard Masses for Use in Soil, Rock, and
coarse-grained soils having fines of low plasticity such as SP,
Construction Materials Testing
SW,SC-SM,orSMsoils.Thetestislimitedtosoilspassingthe
E11 Specification for Woven Wire Test Sieve Cloth and Test
2.00-mm sieve or that fraction of a soil passing a 2.00-mm
Sieves
sieve.
3. Terminology
NOTE 1—Test Method D3152 or Test Method D2325 should be used to
evaluate the capillary-moisture relations of fine-grained soils and coarse-
3.1 All definitions are in accordance with Terminology
grained soils having fines of medium to high plasticity, undisturbed soils,
D653. Terms of particular significance are as follows:
and soils at specific desired units weights.
3.2 capillary fringe zone—the zone above the free water
1.3 The test method is temperature-dependent, and consis-
elevation in which water is held by capillary action.
tent comparable results can be obtained only if the tests are
3.3 centrifuge moisture equivalent—the water content of a
performed under a constant-temperature condition.
soilafterithasbeensaturatedwithwaterandthensubjectedfor
1.4 The values stated in SI units are to be regarded as the
one hour to a centrifugal force equal to 1000 times that of
standard.
gravity.
1.5 This standard does not purport to address all of the
3.4 specific retention—the ratio of the volume of water that
safety concerns, if any, associated with its use. It is the
cannot be drained from a saturated soil under the action of
responsibility of the user of this standard to establish appro-
force of gravity to the total volume of voids.
priate safety and health practices and determine the applica-
3.5 water-holding capacity—the smallest value to which the
bility of regulatory limitations prior to use.
water content of soil or rock can be reduced by gravity
drainage.
2. Referenced Documents
2.1 ASTM Standards:
4. Summary of Test Method
D653 Terminology Relating to Soil, Rock, and Contained
4.1 The centrifuge moisture equivalent of soils is deter-
Fluids
mined by initially air-drying the soil, selecting two 5-g test
D2216 Test Methods for Laboratory Determination of Water
specimens, thoroughly soaking each test specimen, and then
(Moisture) Content of Soil and Rock by Mass
determining the water content of each specimen after it has
D2325 Test Method for Capillary-Moisture Relationships
been centrifuged for 1 h at a force equal to 1000 times that of
for Coarse- and Medium-Textured Soils by Porous-Plate
gravity at a controlled temperature of 20 6 1°C.
5. Significance and Use
This test method is under the jurisdiction ofASTM Committee D18 on Soil and
5.1 Not all water contained in a saturated soil can be
Rock and is the direct responsibility of Subcommittee D18.03 on Texture, Plasticity
removed by gravity drainage. The amount of water retained
and Density Characteristics of Soils.
Current edition approved Feb. 1, 2008. Published March 2008. Originally
after gravity drainage is usually expressed as water holding
approved in 1935. Last previous edition approved in 2001 as D425 – 88 (2001).
capacity or specific retention. It varies with time, and with the
DOI: 10.1520/D0425-88R08.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D425 − 88 (2008)
particle-size distribution and plasticity of the soil (in general, where:
increasing in value with increasing plasticity index).
N = revolutions per minute,
RCF = relative centrifugal force (1000),
5.2 In general, the centrifuge moisture equivalent is based
r = radius of rotation to center of gravity of the test
on the theory of applying a centrifugal force great enough to
specimen, cm, and
reduce the capillary fringe zone enough that it can be ignored
m = mass of the body, taken as unity.
without introducing much error, even in small specimens, and
yet not so great as to withdraw a large proportion of the water
For normal equipment installation, N will equal approxi-
that is held securely above the capillary fringe. For example, if mately 2300 rpm.
a soil will hold water 100 mm by capillarity acting against
6.2 Gooch Crucible—A procelain Gooch crucible having a
gravity,thesoilwilltheoreticallybeabletoholdthewateronly
perforated bottom, a capacity of approximately 25 mL, and a
0.1 mm against a centrifugal force that is 1000 times greater
diameter at bottom of about 20 mm (Fig. 1). Crucibles should
thantheforceofgravity.Ithasbeendeterminedthatforatleast
be numbered and paired in such a way that their masses meet
medium-textured soils (sandy to silty particle-size distribution)
the requirements of the manufacturer of the centrifuge.
the centrifuge moisture equivalent approximates the water
holding capacity and when combined with the bulk density can 6.3 Babcock Trunnion Cups—At least one pair of centrifuge
be used to calculate an approximate specific retention and
cups with caps and with a crucible holder for supporting the
specific yield. These properties when combined with porosity Gooch crucible above the bottom of the cup (Fig. 1). The
can be used to estimate aquifer storage coefficient.
holder shall have sufficient clearance to fit fully within the cup
and short support the cup in such a manner that the water
6. Apparatus
ejected during the centrifuging operation does not come in
contact with the crucible and soil. Cups and crucible holders
6.1 Centrifuge—A centrifuge of such a size and so driven
should be balanced in pairs opposite each other in the centri-
that a force equal to 1000 times the force of gravity may be
fuge and should be numbered in pairs (for example, 1, 1A, 2,
exerted on the center of gravity of the soil specimen for 1 h.
2A, etc.).
The centrifuge chamber shall be capable of maintaining a
controlled temperature of 20 6 1°C. The revolutions per
6.4 Filter Paper—A circular piece of filter paper just large
minute, N,requiredt
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