1、Designation: D4491/D4491M 15Standard Test Methods forWater Permeability of Geotextiles by Permittivity1This standard is issued under the fixed designation D4491/D4491M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of la
2、st revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 These test methods cover procedure
3、s for determiningthe hydraulic conductivity (water permeability) of geotextilesin terms of permittivity under standard testing conditions, inthe uncompressed state. Included are three procedures: theconstant head and falling head methods using a water flowapparatus, and the air flow method using an
4、air flow apparatus.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in n
5、on-conformancewith the standard.1.3 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 standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitati
6、ons prior to use.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD653 Terminology Relating to Soil, Rock, and ContainedFluidsD4439 Terminology for GeosyntheticsD5199 Test Method for Measuring the Nominal Thicknessof GeosyntheticsE691 Practice for Conducting an Interla
7、boratory Study toDetermine the Precision of a Test Method2.2 ASTM Adjuncts:3Detailed Drawings and Materials List for Construction, 10Drawings3. Terminology3.1 Definitions:3.1.1 geotextile, na permeable geosynthetic comprisedsolely of textiles.3.1.2 permeability, nthe rate of flow of a liquid under a
8、differential pressure through a material.3.1.2.1 DiscussionThe nominal thickness is used as it isdifficult to evaluate the pressure on the geotextile during thetest, thereby making it difficult to determine the thickness ofthe fabric under these test conditions.3.1.3 permeability, nof geotextiles, h
9、ydraulic conductiv-ity.3.1.4 permittivity, (), (T1), nof geotextiles, the volu-metric flow rate of water per unit cross sectional area per unithead under laminar flow conditions, in the normal directionthrough a geotextile.3.1.5 For the definitions of other terms relating togeotextiles, refer to Ter
10、minology D4439. For the definitions oftextile terms, refer to Terminology D123. For the definition ofcoefficient of permeability, refer to Terminology D653.4. Summary of Test Method4.1 Water Flow Test MethodsThese test methods describeprocedures for determining the permittivity of geotextiles usingc
11、onstant head or falling head test procedures with a water flowapparatus:4.1.1 Method A - Constant Head TestA head of 50 mm ofwater is maintained on the geotextile throughout the test. Thequantity of flow is measured versus time. The constant headtest is used when the flow rate of water through the g
12、eotextileis so large that it is difficult to obtain readings of head change1These test methods are under the jurisdiction of ASTM Committee D35 onGeosynthetics and are the direct responsibility of Subcommittee D35.03 onPermeability and Filtration.Current edition approved July 1, 2015. Published July
13、 2015. Originally approvedin 1985. Last previous edition approved in 2014 as D4491 99a(2014)1. DOI:10.1520/D4491_D4491M-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, re
14、fer to the standards Document Summary page onthe ASTM website.3Detailed drawings and a materials list for construction are available fromASTM International Headquarters. Order Adjunct No. ADJD4491.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Uni
15、ted States1versus time in the falling head test. The constant head test is thereferee method for this standard.NOTE 1Data has shown agreement between the falling and constanthead methods of determining permittivity of geotextiles.4Selection of thetest method, that is, constant or falling head, is le
16、ft to the technicianperforming the test.4.1.2 Method B - Falling Head TestA column of water isallowed to flow through the geotextile and readings of headchanges versus time are taken. The flow rate of water throughthe geotextile must be slow enough to obtain accurate readings.4.1.3 Method C - Air Fl
17、ow TestA geotextile specimen issubjected to increasing air flow while the flow rate anddifferential pressure are measured. Two flow rate data pointsare obtained at pressures of 250 and 500 Pascals, which areused to determine the Characteristic Flow Equation of thespecimen. The water permittivity at
18、50-mm water head is thencalculated using the conversion algorithm described in thisstandard.5. Significance and Use5.1 These test methods are considered satisfactory for ac-ceptance testing of commercial shipments of geotextiles sincethe methods have been used extensively in the trade foracceptance
19、testing.5.1.1 In case of a dispute arising from differences inreported test results when using these test methods for accep-tance testing of commercial shipments, the purchaser and thesupplier should conduct comparative tests to determine if thereis a statistical bias between their laboratories. Com
20、petentstatistical assistance is recommended for the investigation ofbias.As a minimum, the two parties should take a group of testspecimens that are as homogeneous as possible and that arefrom a lot of material of the type in question. The testspecimens should then be randomly assigned in numbers to
21、each laboratory for testing. The average results from the twolaboratories should be compared using Students t-test forunpaired data and an acceptable probability level chosen by thetwo parties before the start of testing. If a bias is found, eitherits cause must be found and corrected, or the purcha
22、ser and thesupplier must agree to interpret future test results in light of theknown bias.5.1.2 When the dispute involves test results produced witheither the Method B Falling Head Test or the Method C AirFlow Test, the Method A Constant Head Test, performed witha 50-mm head should be used as the re
23、feree method.5.1.3 When the dispute involves Method C, the actual watertemperature used for the water flow tests must be recorded andthe viscosity of water at the test temperature must be used inthe conversion from the air flow to water flow as described inSection 16, without the application of the
24、temperature correc-tion.5.1.4 Permittivity is an indicator of the quantity of waterthat can pass through a geotextile in an isolated condition.5.1.5 As there are many applications and environmentalconditions under which a geotextile may be used, care shouldbe taken when attempting to apply the resul
25、ts of these testmethods 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 permeabilitiescan be misleading. In many instances, it is more significant toevaluate the quantity of water that would pass
26、 through ageotextile under a given head over a particular cross-sectionalarea; this is expressed as permittivity.5.3 If the permeability of an individual geotextile is ofimportance, a nominal coefficient of permeability, as related togeotechnical engineering, may be computed. By multiplyingpermittiv
27、ity times the nominal thickness of the geotextile, asdetermined by Test Method D5199, the nominal coefficient ofpermeability is obtained.NOTE 2The nominal thickness is used as it is difficult to evaluate thepressure on the geotextile during the test, thereby making it difficult todetermine the thick
28、ness of the fabric under these test conditions.6. Apparatus6.1 Water Flow ApparatusThe apparatus for performingthe water flow tests shall conform to one of the followingarrangements:6.1.1 The apparatus must be capable of maintaining aconstant head of water on the geotextile being tested, or6.1.2 The
29、 apparatus must be capable of being used as fallinghead apparatus.6.1.3 The location of the manometer for measuring the headloss in either constant head or falling head methods shall belocated directly beneath the specimen. For the device shown inFig. 1, this may be accomplished by drilling and tapp
30、ing asmall (3-mm) diameter hole in the top plate of the bottomreservoir tank directly beneath the specimen, and attaching themanometer to this plate.6.2 In addition, the apparatus must not be the controllingagent for flow during the test. It will be necessary to establisha calibration curve of volum
31、etric flow rate versus head for theapparatus alone in order to establish compliance with thisrequirement (see 11.7).6.3 Refer to Fig. 1 for a schematic drawing of a device thatconforms to all of the above requirements. The device consistsof an upper and lower unit, which fasten together. Thegeotexti
32、le specimen is positioned in the bottom of the upperunit. There is a standpipe for measuring the constant headvalue. The rotating discharge pipe allows adjustment of thehead of water at the bottom of the specimen.3See ADJD4491.6.4 Air Flow ApparatusThe apparatus for performing theair flow tests shal
33、l conform to the following specifications:6.4.1 Clean Gas Pressure Source, with regulation (filteredair).6.4.2 Pressure SensorPressure measurements must be ob-tained with a digital pressure transducer with an accuracy of65 Pascals.6.4.2.1 The head (upstream) pressure manometer tap mustbe installed i
34、mmediately upstream, within 10 mm, of the testspecimen surface.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D35-1007. ContactASTM CustomerService at serviceastm.org.D4491/D4491M 1526.4.2.2 The tail (downstream) pressure senso
35、r must beinstalled 25 mm or more from the geotextile test specimen, andwithin the 25-mm diameter section.6.4.3 Closed Specimen Holder:6.4.3.1 Specimen holder for the test specimens that fullyconfines the perimeter of the specimen to prevent any lateralpressure losses.6.4.3.2 The specimen flow area s
36、hall be 25-mm diameter.6.4.3.3 The filter holder should be checked for leaks byplacing an impermeable membrane in the holder and increasingthe pressure to the maximum capacity of the pressure sensorand holding it for a period of one minute. The flow ratemeasured during this period must be zero indic
37、ating a leak-freeseal.6.4.4 Metal Punch, used to cut a suitable size geotextilefrom the test sheet to fit the test specimen holder.FIG. 1 Constant and Falling Head Permeability ApparatusD4491/D4491M 1536.4.5 Flow Rate Measurement SensorsThe apparatusshould be equipped with a digital flow meter to me
38、asure theflow rates at the two desired pressures. The flow meter musthave an accuracy of at least 60.5 lpm or 1.0 % of the measuredvalue, whichever is larger.6.4.6 Flow SectionThe geometry of the air flow apparatusat the section where the test specimen is located must have auniform 25-mm pipe diamet
39、er upstream and downstream of thetest specimen for a minimum distance in both directions of50 mm.7. Sampling7.1 Lot SampleAs a lot sample for acceptance testing, takeat random the number of rolls of geotextile directed in anapplicable material specification or other agreement betweenthe purchaser an
40、d the supplier. Consider rolls of geotextile tobe the primary sampling units. If the specification requiressampling during manufacture, select the rolls for the lot sampleat uniformly spaced time intervals throughout the productionperiod.NOTE 3An adequate specification or other agreement between the
41、purchaser and the supplier requires taking into account the variabilitybetween rolls of geotextile and between specimens from a swatch from aroll of geotextile so as to provide a sampling plan with a meaningfulproducers risk, consumers risk, acceptable quality level, and limitingquality level.7.2 La
42、boratory SampleTake for the laboratory sample afull roll width sample extending a minimum of 1 m along theselvage from each sample roll such that the requirements ofSection 9 can be met. Take a sample that will exclude materialfrom the outer wrap of the roll or the inner wrap around thecore unless t
43、he sample is taken at the production site, at whichpoint inner and outer wrap material may be used.8. Test Water Preparation - Water Flow Tests8.1 To provide reproducible test results, the test water usedfor the water flow tests shall be de-aired to bring the dissolvedoxygen content down to a maximu
44、m of six parts per million.The dissolved oxygen content may be determined by eithercommercially available chemical kits or by a dissolved oxygenmeter.NOTE 4The de-airing system may be either a commercially availablesystem or one consisting of a vacuum pump capable of removing aminimum of 150 L/min o
45、f air in connection with a non-collapsible storagetank with a large enough storage capacity for the test series, or at least onespecimen at a time.8.2 Allow the de-aired water to stand in a closed storagetank under a slight vacuum until room temperature is attained.8.3 The test water must be maintai
46、ned at the standardatmosphere for geosynthetic testing which is 21 6 2C.9. Specimen Preparation9.1 To obtain a representative value of permittivity, takefour specimens from each full width laboratory sample asdescribed below.9.2 Referring to Fig. 2, select four specimens, A, B, C, andD, as follows:9
47、.2.1 Select four specimens equally spaced across the widthof the sample. For woven geotextiles, take the test specimensalong a diagonal line extending from the lower left hand cornerto the upper right hand corner of the laboratory sample. Noneof the test specimens shall be closer to the corner of th
48、elaboratory sample than 200 mm 8 in.9.2.2 For the Method C Air Flow tests, take ten testspecimens equally spaced across the width of the sample. Forwoven geotextiles, take the ten test specimens equally spacedalong a diagonal line extending from the lower left hand cornerto the upper right hand corn
49、er of the laboratory sample. Noneof the specimens shall be closer to the edge of the laboratorysample than 200 mm 8 in.9.2.3 Cut specimens shall fit the testing apparatus, forexample, 73 mm 2.87 in. in diameter for the device illustratedin Fig. 1.NOTE 5If the illustrated device is used for the water flow tests, thespecimens are attached to the specimen ring by contact cement.10. Operator Process Control10.1 Water Flow Apparatus:10.1.1 Prepare four specimens of a No. 200 Standard U.S.Mesh Sieve to fit the test apparatus.10.1.2 Following Section
