ASTM D4491-99a(2009)
(Test Method)Standard Test Methods for Water Permeability of Geotextiles by Permittivity
Standard Test Methods for Water Permeability of Geotextiles by Permittivity
SIGNIFICANCE AND USE
These test methods are considered satisfactory for acceptance testing of commercial shipments of geotextiles since the methods have been used extensively in the trade for acceptance testing.
In case of a dispute arising from differences in reported test results when using these test methods for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type in question. The test specimens should then be randomly assigned in numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student's t-test for unpaired data and an acceptable probability level chosen by the two parties before the start of testing. If a bias is found, either its cause must be found and corrected, or the purchaser and the supplier must agree to interpret future test results in light of the known bias.
Permittivity is an indicator of the quantity of water that can pass through a geotextile in an isolated condition.
As there are many applications and environmental conditions under which a geotextile may be used, care should be taken when attempting to apply the results of these test methods to the field performance of a geotextile.
Since there are geotextiles of various thicknesses in use, evaluation in terms of their Darcy coefficient of permeabilities can be misleading. In many instances, it is more significant to evaluate the quantity of water that would pass through a geotextile under a given head over a particular cross-sectional area; this is expressed as permittivity.
If the permeability of an individual geotextile is of importance, a nominal coefficient of permeability, as related to ge...
SCOPE
1.1 These test methods cover 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.
General Information
Relations
Buy Standard
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: D4491 − 99a(Reapproved 2009)
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 (´) 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. Terminology
1.1 These test methods cover procedures for determining 3.1 Definitions:
the hydraulic conductivity (water permeability) of geotextiles 3.1.1 geotechnics, n—the application of scientific methods
in terms of permittivity under standard testing conditions, in and engineering principles to the acquisition, interpretation,
the uncompressed state. Included are two procedures: the and use of knowledge of materials of the earth’s crust to the
constant head method and the falling head method. solution of engineering problems.
3.1.1.1 Discussion—Geotechnics embraces the fields of soil
1.2 The values stated in SI units are to be regarded as the
mechanics, rock mechanics, and many of the engineering
standard. The inch-pound units stated in parentheses are
aspects of geology, geophysics, hydrology, and related sci-
provided for information only.
ences.
1.3 This standard does not purport to address all of the
3.1.2 geotextile, n—a permeable geosynthetic comprised
safety concerns, if any, associated with its use. It is the
solely of textiles.
responsibility of the user of this standard to establish appro-
3.1.3 permeability, n—the rate of flow of a liquid under a
priate safety and health practices and determine the applica-
differential pressure through a material.
bility of regulatory limitations prior to use.
3.1.3.1 Discussion—The nominal thickness is used as it is
2. Referenced Documents
difficult to evaluate the pressure on the geotextile during the
test, thereby making it difficult to determine the thickness of
2.1 ASTM Standards:
the fabric under these test conditions.
D123Terminology Relating to Textiles
3.1.4 permeability, n— of geotextiles, hydraulic conductiv-
D653Terminology Relating to Soil, Rock, and Contained
Fluids ity.
D4439Terminology for Geosynthetics
3.1.5 permittivity, (ψ), (T−1), n—of geotextiles, the volu-
D5199Test Method for Measuring the Nominal Thickness
metric flow rate of water per unit cross sectional area per unit
of Geosynthetics
head under laminar flow conditions, in the normal direction
E691Practice for Conducting an Interlaboratory Study to
through a geotextile.
Determine the Precision of a Test Method
3.1.6 For the definitions of other terms relating to
2.2 ASTM Adjuncts:
geotextiles, refer toTerminology D4439. For the definitions of
Detailed Drawing and Materials List for Construction, 10
textile terms, refer to Terminology D123. For the definition of
Drawings
coefficient of permeability, refer to Terminology D653.
4. Summary of Test Methods
These test methods are under the jurisdiction of ASTM Committee D35 on
4.1 These test methods describe procedures for determining
Geosynthetics and are the direct responsibility of Subcommittee D35.03 on
Permeability and Filtration. the permittivity of geotextiles using constant head or falling
Current edition approved Nov. 1, 2009. Published December 2009. Originally
head test procedures, as follows:
ϵ1
apporoved in 1985. Last previous edition approved in 2004 as D4491–04 . DOI:
4.1.1 ConstantHeadTest—Aheadof50mm(2in.)ofwater
10.1520/D4491-99R09.
is maintained on the geotextile throughout the test. The
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
quantity of flow is measured versus time. The constant head
Standards volume information, refer to the standard’s Document Summary page on
test is used when the flow rate of water through the geotextile
the ASTM website.
3 is so large that it is difficult to obtain readings of head change
Detailed drawings and a materials list for construction are available from
ASTM Headquarters. Request adjunct No. ADJD4491. versus time in the falling head test.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4491 − 99a (2009)
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
5. Significance and Use
requirement (see 11.7).
5.1 These test methods are considered satisfactory for ac-
6.3 Refer to Fig. 1 for a schematic drawing of a device that
ceptance testing of commercial shipments of geotextiles since
conforms to all of the above requirements.The device consists
the methods have been used extensively in the trade for
of an upper and lower unit, which fasten together. The
acceptance testing.
geotextile specimen is positioned in the bottom of the upper
5.1.1 In case of a dispute arising from differences in
unit. There is a standpipe for measuring the constant head
reported test results when using these test methods for accep-
value. The rotating discharge pipe allows adjustment of the
tance testing of commercial shipments, the purchaser and the
head of water at the bottom of the specimen. See ADJD4491.
suppliershouldconductcomparativeteststodetermineifthere
NOTE 3—The location of the manometer for measuring the headloss in
is a statistical bias between their laboratories. Competent
either the constant head or falling head method shall be located directly
statistical assistance is recommended for the investigation of
beneath the specimen. For the device shown in Fig. 1, this may be
bias.Asaminimum,thetwopartiesshouldtakeagroupoftest
accomplished by drilling a small (3mm; ⁄8 in) diameter hole in the top
specimens that are as homogeneous as possible and that are plate of the bottom reservoir tank directly beneath the specimen, and
attaching the manometer to this plate.
from a lot of material of the type in question. The test
specimens should then be randomly assigned in numbers to
7. Sampling
each laboratory for testing. The average results from the two
laboratories should be compared using Student’s t-test for
7.1 LotSample—Asalotsampleforacceptancetesting,take
unpaireddataandanacceptableprobabilitylevelchosenbythe
at random the number of rolls of geotextile directed in an
two parties before the start of testing. If a bias is found, either
applicable material specification or other agreement between
itscausemustbefoundandcorrected,orthepurchaserandthe
the purchaser and the supplier. Consider rolls of geotextile to
suppliermustagreetointerpretfuturetestresultsinlightofthe
be the primary sampling units. If the specification requires
known bias.
samplingduringmanufacture,selecttherollsforthelotsample
5.1.2 Permittivity is an indicator of the quantity of water
at uniformly spaced time intervals throughout the production
that can pass through a geotextile in an isolated condition.
period.
5.1.3 As there are many applications and environmental
NOTE 4—An adequate specification or other agreement between the
conditions under which a geotextile may be used, care should
purchaser and the supplier requires taking into account the variability
be taken when attempting to apply the results of these test
between rolls of geotextile and between specimens from a swatch from a
methods to the field performance of a geotextile.
roll of geotextile so as to provide a sampling plan with a meaningful
producer’s risk, consumer’s risk, acceptable quality level, and limiting
5.2 Sincetherearegeotextilesofvariousthicknessesinuse,
quality level.
evaluation in terms of their Darcy coefficient of permeabilities
7.2 Laboratory Sample—Take for the laboratory sample a
can be misleading. In many instances, it is more significant to
full roll width sample extending a minimum of 1 m along the
evaluate the quantity of water that would pass through a
selvage from each sample roll such that the requirements of
geotextile under a given head over a particular cross-sectional
Section 9 can be met.Take a sample that will exclude material
area; this is expressed as permittivity.
from the outer wrap of the roll or the inner wrap around the
5.3 If the permeability of an individual geotextile is of
core unless the sample is taken at the production site, at which
importance, a nominal coefficient of permeability, as related to
point inner and outer wrap material may be used.
geotechnical engineering, may be computed. By multiplying
permittivity times the nominal thickness of the geotextile, as
8. Test Water Preparation
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
NOTE 2—The nominal thickness is used as it is difficult to evaluate the
(Hg)foraperiodoftimetobringthedissolvedoxygencontent
pressure on the geotextile during the test, thereby making it difficult to
down to a maximum of six parts per million. The dissolved
determine the thickness of the fabric under these test conditions.
oxygen content may be determined by either commercially
6. Apparatus
available chemical kits or by a dissolved oxygen meter.
6.1 The apparatus shall conform to one of the following
NOTE 5—The de-airing system may be either a commercially available
arrangements:
system or one consisting of a vacuum pump capable of removing a
minimumof150L/minofairinconnectionwithanon-collapsiblestorage
Supporting data have been filed atASTM International Headquarters and may tankwithalargeenoughstoragecapacityforthetestseries,oratleastone
be obtained by requesting Research Report RR: RR:D35-1007. specimen at a time.
D4491 − 99a (2009)
FIG. 1 Constant and Falling Head Permeability Apparatus
8.2 Allow the de-aired water to stand in a closed storage 9.2.1 Selectfourspecimensequallyspacedalongadiagonal
tank under a slight vacuum until room temperature is attained. line extending from the lower left hand corner to the upper
righthandcornerofthelaboratorysample.NeitherspecimenA
9. Specimen Preparation
or D shall be closer to the corner of the laboratory sample than
9.1 To obtain a representative value of permittivity, take
200 mm (8 in.).
four specimens from each full width laboratory sample as
9.2.2 Take specimenAat the center of the sample, B at one
described below.
corner (center located 200 mm (8 in.) from the corner), C
midway betweenAand B, and D the same distance fromAas
9.2 Referring to Fig. 2, select four specimens,A, B, C, and
D, as follows: C, located on a line with A, B, and C.
D4491 − 99a (2009)
FIG. 2 Specimen Locations
9.2.3 Cut specimens shall fit the testing apparatus, for water on the geotextile. This is the head (h) under which the
example,73mm(2.87in.)indiameterforthedeviceillustrated test will be performed initially.
in Fig. 1.
11.5 Submergeatubeattachedtoasourceofvacuumtojust
9.3 Conditionthespecimenbysoakinginaclosedcontainer above (10 mm (0.5 in.)) the surface of the geotextile, moving
of de-aired water, at room conditions, for a period of 2 h. The thetubegentlyoverthesurfacewhileapplyingaslightvacuum
minimum specimen diameter is to be 50 mm (2 in.). in order to remove any trapped air that may be in or on the
specimen.Ifnecessary,readjusttheheadto50mm(2in.)after
NOTE 6—If the illustrated device is used, the specimens are attached to
removing the vacuum.
the specimen ring by contact cement.
11.6 Record the values of time (t ), quantity of flow (Q)as
10. Operator Process Control
collected from the discharge pipe, and water temperature (T),
10.1 Prepare four specimens of Standard U.S. Mesh Sieve
holding the head at 50 mm (2 in.). Make at least five readings
to fit the test apparatus.
per specimen and determine an average value of permittivity
for the specimen.
10.2 Following Section 11 or Section 13, depending on the
methodtobeusedforthegeotextilespecimens,performtesting
NOTE 8—The quantity of flow may be measured in millilitres and then
on each mesh specimen.
converted to cubic millimetres for the computation of permittivity (1
mL=1000 mm ).
10.3 Based on an interlaboratory test, involving seven
11.7 Afterthefirstspecimenhasbeentestedundera50-mm
laboratories, the permittivity of No 200 Standard US Mesh
−1
(2-in.) head, using the same specimen, start with a 10-mm
Sieve material has been determined to be 5.00 s , with a
( ⁄8-in.) head and repeat the procedure. Increase the head by 5
standard deviation of 0.65.
mm ( ⁄16 in.) after every five readings. Increase the head until
10.3.1 New operator process control shall be performed
a75-mm(3-in.)headisreached.Usethisdatatodeterminethe
until it is demonstrated that the operator is proficient in test
region of laminar flow. Plot volumetric flow rate, v, (where v
performance as demonstrated by obtaining the value of per-
equals Q/At , values defined in 12.1) versus head.The quantity
mittivity stated in 10.3, plus or minus two standard deviations.
of flow (Q) should be corrected to 20°C (68°F). The initial
10.3.2 Following initial proficiency testing, the operator
straight line portion of the plot defines the region of laminar
shall perform process control testing on a semi-annual basis.
flow. If the 50-mm head is outside the region of laminar flow,
CONSTANT HEAD TEST
repeat the test procedure using the head of water in the
mid-region of laminar flow.
11. Procedure
11.7.1 Compare the data from 11.7 with the apparatus
11.1 Assemble the apparatus with the specimen in place.
calibration curve referred to in 6.2. The apparatus calibration
plotofvolumetricflowrateversusheadshouldplotwellabove
11.2 Open the bleed valve and backfill the system through
the same plot for the geotextile specimen (see Fig. 3). If the
the standpip
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation:D4491–99a (Reapproved 2004) Designation:D4491–99a (Reapproved
2009)
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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—Adjunct references were corrected editorially in June 2006.
1. Scope
1.1 Thesetestmethodscoverproceduresfordeterminingthehydraulicconductivity(waterpermeability)ofgeotextilesinterms
ofpermittivityunderstandardtestingconditions,intheuncompressedstate.Includedaretwoprocedures:theconstantheadmethod
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.
2. Referenced Documents
2.1 ASTM Standards:
D123 Terminology Relating to Textiles
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D4439 Terminology for Geosynthetics
D5199 Test Method for Measuring the Nominal Thickness of Geosynthetics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 ASTM Adjuncts:
Detailed Drawing and Materials List for Construction, 10 Drawings
3. Terminology
3.1 Definitions:
3.1.1 geotechnics, n—the application of scientific methods and engineering principles to the acquisition, interpretation, and use
of knowledge of materials of the earth’s crust to the solution of engineering problems.
3.1.1.1 Discussion—Geotechnics embraces the fields of soil mechanics, rock mechanics, and many of the engineering aspects
of geology, geophysics, hydrology, and related sciences.
3.1.2 geotextile, n—a permeable geosynthetic comprised solely of textiles.
3.1.3 permeability, n—the rate of flow of a liquid under a differential pressure through a material.
3.1.3.1 Discussion—The nominal thickness is used as it is difficult to evaluate the pressure on the geotextile during the test,
thereby making it difficult to determine the thickness of the fabric under these test conditions.
3.1.4 permeability, n— of geotextiles, hydraulic conductivity.
3.1.5 permittivity, (c), (T−1), n—of geotextiles, the volumetric flow rate of water per unit cross sectional area per unit head
under laminar flow conditions, in the normal direction through a geotextile.
These test methods are under the jurisdiction ofASTM Committee D35 on Geosynthetics and are the direct responsibility of Subcommittee D35.03 on Permeability and
Filtration.
Current edition approved April 7, 2006. Published March 2000. Originally apporoved in 1985. Last previous edition approved in 1999 as D4491–99a. DOI:
10.1520/D4491-99AR04E01.
´1
Current edition approved Nov. 1, 2009. Published December 2009. Originally apporoved in 1985. Last previous edition approved in 2004 as D4491–04 . DOI:
10.1520/D4491-99R09.
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book ofASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Detailed drawings and a materials list for construction are available from ASTM Headquarters. Request adjunct No. ADJD4491.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4491–99a (2009)
3.1.6 For the definitions of other terms relating to geotextiles, refer to Terminology D4439. For the definitions of textile terms,
refer to Terminology D123. For the definition of coefficient of permeability, refer to Terminology D653.
4. Summary of Test Methods
4.1 These test methods describe procedures for determining the permittivity of geotextiles using constant head or falling head
test procedures, as follows:
4.1.1 Constant Head Test—Ahead of 50 mm (2 in.) of water is maintained on the geotextile throughout the test. The quantity
of flow is measured versus time. The constant head test is used when the flow rate of water through the geotextile is so large that
it is difficult to obtain readings of head change versus time in the falling head test.
NOTE 1—Data has shown agreement between the falling and constant head methods of determining permittivity of geotextiles. Selection of the test
method, that is, constant or falling head, is left to the technician performing the test.
4.1.2 Falling Head Test—Acolumnofwaterisallowedtoflowthroughthegeotextileandreadingsofheadchangesversustime
are taken. The flow rate of water through the geotextile must be slow enough to obtain accurate readings.
5. Significance and Use
5.1 These test methods are considered satisfactory for acceptance testing of commercial shipments of geotextiles since the
methods have been used extensively in the trade for acceptance testing.
5.1.1 In case of a dispute arising from differences in reported test results when using these test methods for acceptance testing
ofcommercialshipments,thepurchaserandthesuppliershouldconductcomparativeteststodetermineifthereisastatisticalbias
between their laboratories. Competent statistical assistance is recommended for the investigation of bias.As a minimum, the two
parties should take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type
in question. The test specimens should then be randomly assigned in numbers to each laboratory for testing. The average results
from the two laboratories should be compared using Student’s t-test for unpaired data and an acceptable probability level chosen
by the two parties before the start of testing. If a bias is found, either its cause must be found and corrected, or the purchaser and
the supplier must agree to interpret future test results in light of the known bias.
5.1.2 Permittivity is an indicator of the quantity of water that can pass through a geotextile in an isolated condition.
5.1.3 As there are many applications and environmental conditions under which a geotextile may be used, care should be taken
when attempting to apply the results of these test methods to the field performance of a geotextile.
5.2 Since there are geotextiles of various thicknesses in use, evaluation in terms of their Darcy coefficient of permeabilities can
bemisleading.Inmanyinstances,itismoresignificanttoevaluatethequantityofwaterthatwouldpassthroughageotextileunder
a given head over a particular cross-sectional area; this is expressed as permittivity.
5.3 If the permeability of an individual geotextile is of importance, a nominal coefficient of permeability, as related to
geotechnical engineering, may be computed. By multiplying permittivity times the nominal thickness of the geotextile, as
determined by Test Method D5199, the nominal coefficient of permeability is obtained.
NOTE 2—Thenominalthicknessisusedasitisdifficulttoevaluatethepressureonthegeotextileduringthetest,therebymakingitdifficulttodetermine
the thickness of the fabric under these test conditions.
6. Apparatus
6.1 The apparatus shall conform to one of the following arrangements:
6.1.1 The apparatus must be capable of maintaining a constant head of water on the geotextile being tested, or
6.1.2 The apparatus must be capable of being used as falling head apparatus.
6.2 In addition, the apparatus must not be the controlling agent for flow during the test. It will be necessary to establish a
calibrationcurveofvolumetricflowrateversusheadfortheapparatusaloneinordertoestablishcompliancewiththisrequirement
(see 11.7).
6.3 Refer to Fig. 1 for a schematic drawing of a device that conforms to all of the above requirements. The device consists of
an upper and lower unit, which fasten together. The geotextile specimen is positioned in the bottom of the upper unit. There is a
standpipe for measuring the constant head value.The rotating discharge pipe allows adjustment of the head of water at the bottom
of the specimen. See ADJD4491.
NOTE 3—Thelocationofthemanometerformeasuringtheheadlossineithertheconstantheadorfallingheadmethodshallbelocateddirectlybeneath
the specimen. For the device shown in Fig. 1, this may be accomplished by drilling a small (3mm; ⁄8 in) diameter hole in the top plate of the bottom
reservoir tank directly beneath the specimen, and attaching the manometer to this plate.
7. Sampling
7.1 Lot Sample—As a lot sample for acceptance testing, take at random the number of rolls of geotextile directed in an
applicable material specification or other agreement between the purchaser and the supplier. Consider rolls of geotextile to be the
Data available from ASTM Headquarters. Request RR: D-35-1007.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR: D35-1007.
D4491–99a (2009)
FIG. 1 Constant and Falling Head Permeability Apparatus
primary sampling units. If the specification requires sampling during manufacture, select the rolls for the lot sample at uniformly
spaced time intervals throughout the production period.
NOTE 4—Anadequatespecificationorotheragreementbetweenthepurchaserandthesupplierrequirestakingintoaccountthevariabilitybetweenrolls
of geotextile and between specimens from a swatch from a roll of geotextile so as to provide a sampling plan with a meaningful producer’s risk,
consumer’s risk, acceptable quality level, and limiting quality level.
7.2 Laboratory Sample—Takeforthelaboratorysampleafullrollwidthsampleextendingaminimumof1malongtheselvage
from each sample roll such that the requirements of Section 9 can be met.Take a sample that will exclude material from the outer
wrap of the roll or the inner wrap around the core unless the sample is taken at the production site, at which point inner and outer
wrap material may be used.
D4491–99a (2009)
8. Test Water Preparation
8.1 To provide reproducible test results, the test water shall be de-aired under a vacuum of 710 mm (28 in.) of mercury (Hg)
for a period of time to bring the dissolved oxygen content down to a maximum of six parts per million. The dissolved oxygen
content may be determined by either commercially available chemical kits or by a dissolved oxygen meter.
NOTE 5—The de-airing system may be either a commercially available system or one consisting of a vacuum pump capable of removing a minimum
of 150 L/min of air in connection with a non-collapsible storage tank with a large enough storage capacity for the test series, or at least one specimen
at a time.
8.2 Allow the de-aired water to stand in a closed storage tank under a slight vacuum until room temperature is attained.
9. Specimen Preparation
9.1 To obtain a representative value of permittivity, take four specimens from each full width laboratory sample as described
below.
9.2 Referring to Fig. 2, select four specimens, A, B, C, and D, as follows:
9.2.1 Select four specimens equally spaced along a diagonal line extending from the lower left hand corner to the upper right
hand corner of the laboratory sample. Neither specimenAor D shall be closer to the corner of the laboratory sample than 200 mm
(8 in.).
9.2.2 Take specimenAat the center of the sample, B at one corner (center located 200 mm (8 in.) from the corner), C midway
between A and B, and D the same distance from A as C, located on a line with A, B, and C.
9.2.3 Cut specimens shall fit the testing apparatus, for example, 73 mm (2.87 in.) in diameter for the device illustrated in Fig.
1.
9.3 Condition the specimen by soaking in a closed container of de-aired water, at room conditions, for a period of 2 h. The
minimum specimen diameter is to be 50 mm (2 in.).
NOTE 6—If the illustrated device is used, the specimens are attached to the specimen ring by contact cement.
10. Operator Process Control
10.1 Prepare four specimens of Standard U.S. Mesh Sieve to fit the test apparatus.
10.2 Following Section 11 or Section 13, depending on the method to be used for the geotextile specimens, perform testing on
each mesh specimen.
10.3 Basedonaninterlaboratorytest,involvingsevenlaboratories,thepermittivityofNo200StandardUSMeshSievematerial
−1
has been determined to be 5.00 s , with a standard deviation of 0.65.
10.3.1 Newoperatorprocesscontrolshallbeperformeduntilitisdemonstratedthattheoperatorisproficientintestperformance
as demonstrated by obtaining the value of permittivity stated in 10.3, plus or minus two standard deviations.
10.3.2 Following initial proficiency testing, the operator shall perform process control testing on a semi-annual basis.
CONSTANT HEAD TEST
11. Procedure
11.1 Assemble the apparatus with the specimen in place.
11.2 Open the bleed valve and backfill the system through the standpipe or discharge pipe, with de-aired water. Backfilling in
this manner forces any trapped air out of the system and the geotextile.
NOTE 7—The water should be at the bottom level of the specimen at the time of specimen installation.
11.3 Close the bleed valve once water flows from it. Continue to fill the apparatus with de-aired water until the water level
reaches the overflow.
FIG. 2 Specimen Locations
D4491–99a (2009)
11.4 With water flowing into the system through the water inlet, adjust the discharge pipe along with the rate of water flowing
into the apparatus to obtain a 50-mm (2-in.) head of water on the geotextile. This is the head (h) under which the test will be
performed initially.
11.5 Submerge a tube attached to a source of vacuum to just above (10 mm (0.5 in.)) the surface of the geotextile, moving the
tube gently over the surface while applying a slight vacuum in order to remove any trapped air that may be in or on the specimen.
If necessary, readjust the head to 50 mm (2 in.) after removing the vacuum.
11.6 Recordthevaluesoftime(t),quantityofflow(Q)ascollectedfromthedischargepipe,andwatertemperature(T),holding
the head at 50 mm (2
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.