ASTM D4491-99a
(Test Method)Standard Test Methods for Water Permeability of Geotextiles by Permittivity
Standard Test Methods for Water Permeability of Geotextiles by Permittivity
SCOPE
1.1 These test methods provide procedures for determining the hydraulic conductivity (water permeability) of geotextiles in terms of permittivity under standard testing conditions, in the uncompressed state. Included are two procedures: the constant head method and the falling head method.
1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units stated in parentheses are provided for information only.
1.3 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.
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Designation:D4491–99a
Standard Test Methods for
Water Permeability of Geotextiles by Permittivity
This standard is issued under the fixed designation D4491; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 3.1.1 geotechnics, n—the application of scientific methods
and engineering principles to the acquisition, interpretation,
1.1 These test methods cover procedures for determining
and use of knowledge of materials of the earth’s crust to the
the hydraulic conductivity (water permeability) of geotextiles
solution of engineering problems.
in terms of permittivity under standard testing conditions, in
3.1.1.1 Discussion—Geotechnicsembracesthefieldsofsoil
the uncompressed state. Included are two procedures: the
mechanics, rock mechanics, and many of the engineering
constant head method and the falling head method.
aspects of geology, geophysics, hydrology, and related sci-
1.2 The values stated in SI units are to be regarded as the
ences.
standard. The inch-pound units stated in parentheses are
3.1.2 geotextile, n—a permeable geosynthetic comprised
provided for information only.
solely of textiles.
1.3 This standard does not purport to address all of the
3.1.3 permeability, n—the rate of flow of a liquid under a
safety concerns, if any, associated with its use. It is the
differential pressure through a material.
responsibility of the user of this standard to establish appro-
3.1.3.1 Discussion—The nominal thickness is used as it is
priate safety and health practices and determine the applica-
difficult to evaluate the pressure on the geotextile during the
bility of regulatory limitations prior to use.
test, thereby making it difficult to determine the thickness of
2. Referenced Documents the fabric under these test conditions.
3.1.4 permeability, n—of geotextiles, hydraulic conductiv-
2.1 ASTM Standards:
ity.
D123 Terminology Relating to Textiles
3.1.5 permittivity, (c), (T−1), n—of geotextiles, the volu-
D653 Terminology Relating to Soil, Rock, and Contained
metric flow rate of water per unit cross sectional area per unit
Fluids
head under laminar flow conditions, in the normal direction
D4439 Terminology for Geotextiles
through a geotextile.
D5199 Test Method for Measuring Nominal Thickness of
3.1.6 For the definitions of other terms relating to geotex-
Geotextiles and Geomembranes
tiles,refertoTerminologyD4439.Forthedefinitionsoftextile
E691 Practice for Conducting an Interlaboratory Study to
terms, refer to Terminology D123. For the definition of
Determine the Precision of a Test Method
coefficient of permeability, refer to Terminology D653.
3. Terminology
4. Summary of Test Methods
3.1 Definitions:
4.1 These test methods describe procedures for determining
the permittivity of geotextiles using constant head or falling
These test methods are under the jurisdiction of ASTM Committee D-35 on
head test procedures, as follows:
Geosynthetics and are the direct responsibility of Subcommittee D35.03 on
4.1.1 ConstantHeadTest—Aheadof50mm(2in.)ofwater
Permeability and Filtration.
is maintained on the geotextile throughout the test. The
Current edition approved Dec. 10, 1999. Published March 2000. Originally
published as D4491–85. Last previous edition D4491–99. quantity of flow is measured versus time. The constant head
Annual Book of ASTM Standards, Vol 07.01.
test is used when the flow rate of water through the geotextile
Annual Book of ASTM Standards, Vol 04.08.
is so large that it is difficult to obtain readings of head change
Annual Book of ASTM Standards, Vol 04.13.
versus time in the falling head test.
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.
D4491–99a
NOTE 1—Data has shown agreement between the falling and constant
6.1.1 The apparatus must be capable of maintaining a
head methods of determining permittivity of geotextiles. Selection of the
constant head of water on the geotextile being tested, or
test method, that is, constant or falling head, is left to the technician
6.1.2 Theapparatusmustbecapableofbeingusedasfalling
performing the test.
head apparatus.
4.1.2 Falling Head Test—A column of water is allowed to
6.2 In addition, the apparatus must not be the controlling
flow through the geotextile and readings of head changes
agent for flow during the test. It will be necessary to establish
versus time are taken. The flow rate of water through the
a calibration curve of volumetric flow rate versus head for the
geotextile must be slow enough to obtain accurate readings.
apparatus alone in order to establish compliance with this
requirement (see 11.7).
5. Significance and Use
6.3 Refer to Fig. 1 for a schematic drawing of a device that
5.1 These test methods are considered satisfactory for ac-
conforms to all of the above requirements.The device consists
ceptance testing of commercial shipments of geotextiles since
of an upper and lower unit, which fasten together. The
the methods have been used extensively in the trade for
geotextile specimen is positioned in the bottom of the upper
acceptance testing.
unit. There is a standpipe for measuring the constant head
5.1.1 In case of a dispute arising from differences in
value. The rotating discharge pipe allows adjustment of the
reported test results when using these test methods for accep-
head of water at the bottom of the specimen.
tance testing of commercial shipments, the purchaser and the
NOTE 3—The location of the manometer for measuring the headloss in
suppliershouldconductcomparativeteststodetermineifthere
either the constant head or falling head method shall be located directly
is a statistical bias between their laboratories. Competent
beneath the specimen. For the device shown in Fig. 1, this may be
statistical assistance is recommended for the investigation of 1
accomplished by drilling a small (3mm; ⁄8 in) diameter hole in the top
bias.Asaminimum,thetwopartiesshouldtakeagroupoftest
plate of the bottom reservoir tank directly beneath the specimen, and
attaching the manometer to this plate.
specimens that are as homogeneous as possible and that are
from a lot of material of the type in question. The test
7. Sampling
specimens should then be randomly assigned in numbers to
7.1 Lot Sample—As a lot sample for acceptance testing,
each laboratory for testing. The average results from the two
take at random the number of rolls of geotextile directed in an
laboratories should be compared using Student’s t-test for
applicable material specification or other agreement between
unpaireddataandanacceptableprobabilitylevelchosenbythe
the purchaser and the supplier. Consider rolls of geotextile to
two parties before the start of testing. If a bias is found, either
be the primary sampling units. If the specification requires
itscausemustbefoundandcorrected,orthepurchaserandthe
samplingduringmanufacture,selecttherollsforthelotsample
suppliermustagreetointerpretfuturetestresultsinlightofthe
at uniformly spaced time intervals throughout the production
known bias.
period.
5.1.2 Permittivity is an indicator of the quantity of water
that can pass through a geotextile in an isolated condition.
NOTE 4—An adequate specification or other agreement between the
5.1.3 As there are many applications and environmental
purchaser and the supplier requires taking into account the variability
conditions under which a geotextile may be used, care should between rolls of geotextile and between specimens from a swatch from a
roll of geotextile so as to provide a sampling plan with a meaningful
be taken when attempting to apply the results of these test
producer’s risk, consumer’s risk, acceptable quality level, and limiting
methods to the field performance of a geotextile.
quality level.
5.2 Sincetherearegeotextilesofvariousthicknessesinuse,
7.2 Laboratory Sample—Take for the laboratory sample a
evaluation in terms of their Darcy coefficient of permeabilities
full roll width sample extending a minimum of 1 m along the
can be misleading. In many instances, it is more significant to
selvage from each sample roll such that the requirements of
evaluate the quantity of water that would pass through a
Section 9 can be met.Take a sample that will exclude material
geotextile under a given head over a particular cross-sectional
from the outer wrap of the roll or the inner wrap around the
area; this is expressed as permittivity.
core unless the sample is taken at the production site, at which
5.3 If the permeability of an individual geotextile is of
point inner and outer wrap material may be used.
importance, a nominal coefficient of permeability, as related to
geotechnical engineering, may be computed. By multiplying
8. Test Water Preparation
permittivity times the nominal thickness of the geotextile, as
determined by Test Method D5199, the nominal coefficient of 8.1 To provide reproducible test results, the test water shall
permeability is obtained. be de-aired under a vacuum of 710 mm (28 in.) of mercury
(Hg)foraperiodoftimetobringthedissolvedoxygencontent
NOTE 2—The nominal thickness is used as it is difficult to evaluate the
down to a maximum of six parts per million. The dissolved
pressure on the geotextile during the test, thereby making it difficult to
oxygen content may be determined by either commercially
determine the thickness of the fabric under these test conditions.
available chemical kits or by a dissolved oxygen meter.
6. Apparatus
NOTE 5—The de-airing system may be either a commercially available
6.1 The apparatus shall conform to one of the following
system or one consisting of a vacuum pump capable of removing a
arrangements:
Detailed drawings and a materials list for construction are available at a
Data available from ASTM Headquarters. Request RR: D-35-1007. nominal cost through ASTM Headquarters. Request adjunct No. ADJD4491.
D4491–99a
FIG. 1 Constant and Falling Head Permeability Apparatus
minimumof150L/minofairinconnectionwithanon-collapsiblestorage
9.2 Referring to Fig. 2, select four specimens,A, B, C, and
tankwithalargeenoughstoragecapacityforthetestseries,oratleastone
D, as follows:
specimen at a time.
9.2.1 Selectfourspecimensequallyspacedalongadiagonal
8.2 Allow the de-aired water to stand in a closed storage
line extending from the lower left hand corner to the upper
tank under a slight vacuum until room temperature is attained.
righthandcornerofthelaboratorysample.NeitherspecimenA
or D shall be closer to the corner of the laboratory sample than
9. Specimen Preparation
200 mm (8 in.).
9.1 To obtai
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