1、Designation: D 4491 99a (Reapproved 2004)e1Standard Test Methods forWater Permeability of Geotextiles by Permittivity1This standard is issued under the fixed designation D 4491; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript 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.e1NOTEAdjunct references were corrected e
3、ditorially in June 2006.1. Scope1.1 These test methods cover procedures for determiningthe hydraulic conductivity (water permeability) of geotextilesin terms of permittivity under standard testing conditions, inthe uncompressed state. Included are two procedures: theconstant head method and the fall
4、ing head method.1.2 The values stated in SI units are to be regarded as thestandard. The inch-pound units stated in parentheses areprovided for information only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the us
5、er of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 123 Terminology Relating to TextilesD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 4439 Termi
6、nology for GeotextilesD 5199 Test Method for Measuring Nominal Thickness ofGeotextiles and GeomembranesE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ASTM Adjuncts:Detailed Drawing and Materials List for Construction, 10Drawings33. Terminology3.1
7、 Definitions:3.1.1 geotechnics, nthe application of scientific methodsand engineering principles to the acquisition, interpretation,and use of knowledge of materials of the earths crust to thesolution of engineering problems.3.1.1.1 DiscussionGeotechnics embraces the fields of soilmechanics, rock me
8、chanics, and many of the engineeringaspects of geology, geophysics, hydrology, and related sci-ences.3.1.2 geotextile, na permeable geosynthetic comprisedsolely of textiles.3.1.3 permeability, nthe rate of flow of a liquid under adifferential pressure through a material.3.1.3.1 DiscussionThe nominal
9、 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.3.1.4 permeability, nof geotextiles, hydraulic conductiv-ity.3.1.5 permittivity, (c), (T1), nof geotextiles,
10、 the volu-metric flow rate of water per unit cross sectional area per unithead under laminar flow conditions, in the normal directionthrough a geotextile.3.1.6 For the definitions of other terms relating to geotex-tiles, refer to Terminology D 4439. For the definitions of textileterms, refer to Term
11、inology D 123. For the definition ofcoefficient of permeability, refer to Terminology D 653.4. Summary of Test Methods4.1 These test methods describe procedures for determiningthe permittivity of geotextiles using constant head or fallinghead test procedures, as follows:4.1.1 Constant Head TestAhead
12、 of 50 mm (2 in.) of wateris 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 geotextileis so large that it is difficult to obtain readings of head changeversus time in the falling hea
13、d test.NOTE 1Data has shown agreement between the falling and constant1These 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 Dec. 10, 1999. Published March 20
14、00. Originallyapporoved in 1985. Last previous edition approved in 1999 as D 4491 99a.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, refer to the standards Document Summary
15、 page onthe ASTM website.3Detailed drawings and a materials list for construction are available fromASTM Headquarters. Request adjunct No. ADJD4491.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.head methods of determining permittiv
16、ity of geotextiles.4Selection of thetest method, that is, constant or falling head, is left to the technicianperforming the test.4.1.2 Falling Head TestA column of water is allowed toflow through the geotextile and readings of head changesversus time are taken. The flow rate of water through thegeot
17、extile must be slow enough to obtain accurate readings.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 testing.5.1.1 In case of a dispute ar
18、ising 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. Competentstatistical assistance is recom
19、mended 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 toeach laboratory for testing. The aver
20、age 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 purchaser and thesupplier must agree to int
21、erpret future test results in light of theknown bias.5.1.2 Permittivity is an indicator of the quantity of waterthat can pass through a geotextile in an isolated condition.5.1.3 As there are many applications and environmentalconditions under which a geotextile may be used, care shouldbe taken when
22、attempting to apply the results 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 quan
23、tity of water that would pass 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 comp
24、uted. By multiplyingpermittivity times the nominal thickness of the geotextile, asdetermined by Test Method D 5199, 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 d
25、ifficult todetermine the thickness of the fabric under these test conditions.6. Apparatus6.1 The apparatus 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 apparatus must be capabl
26、e of being used as fallinghead apparatus.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 volumetric flow rate versus head for theapparatus alone in order to establish compliance with thisrequirement (se
27、e 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. Thegeotextile specimen is positioned in the bottom of the upperunit. There is a standpipe for measuring the constant he
28、advalue. The rotating discharge pipe allows adjustment of thehead of water at the bottom of the specimen.3See ADJD4491.NOTE 3The location of the manometer for measuring the headloss ineither the constant head or falling head method shall be located directlybeneath the specimen. For the device shown
29、in Fig. 1, this may beaccomplished by drilling a small (3mm;18 in) diameter hole in the topplate of the bottom reservoir tank directly beneath the specimen, andattaching the manometer to this plate.7. Sampling7.1 Lot SampleAs a lot sample for acceptance testing,take at random the number of rolls of
30、geotextile directed in anapplicable material specification or other agreement betweenthe purchaser and 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 int
31、ervals throughout the productionperiod.NOTE 4An adequate specification or other agreement between thepurchaser 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
32、 meaningfulproducers risk, consumers risk, acceptable quality level, and limitingquality level.7.2 Laboratory 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 sampl
33、e that will exclude materialfrom the outer wrap of the roll or the inner wrap around thecore unless the sample is taken at the production site, at whichpoint inner and outer wrap material may be used.8. Test Water Preparation8.1 To provide reproducible test results, the test water shallbe de-aired u
34、nder a vacuum of 710 mm (28 in.) of mercury(Hg) for a period of time to bring the dissolved oxygen contentdown to a maximum of six parts per million. The dissolvedoxygen content may be determined by either commerciallyavailable chemical kits or by a dissolved oxygen meter.NOTE 5The de-airing system
35、may be either a commercially availablesystem or one consisting of a vacuum pump capable of removing aminimum of 150 L/min of 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.4Data available from ASTM Head
36、quarters. Request RR: D-35-1007.D 4491 99a (2004)e128.2 Allow the de-aired water to stand in a closed storagetank under a slight vacuum until room temperature is attained.9. Specimen Preparation9.1 To obtain a representative value of permittivity, takefour specimens from each full width laboratory s
37、ample asdescribed below.9.2 Referring to Fig. 2, select four specimens, A, B, C, andD, as follows:9.2.1 Select four specimens equally spaced along a diagonalline extending from the lower left hand corner to the upperright hand corner of the laboratory sample. Neither specimenAor D shall be closer to
38、 the corner of the laboratory sample than200 mm (8 in.).9.2.2 Take specimen A at the center of the sample, B at onecorner (center located 200 mm (8 in.) from the corner), Cmidway between A and B, and D the same distance from A asC, located on a line with A, B, and C.FIG. 1 Constant and Falling Head
39、Permeability ApparatusD 4491 99a (2004)e139.2.3 Cut specimens shall fit the testing apparatus, forexample, 73 mm (2.87 in.) in diameter for the device illustratedin Fig. 1.9.3 Condition the specimen by soaking in a closed containerof de-aired water, at room conditions, for a period of 2 h. Theminimu
40、m specimen diameter is to be 50 mm (2 in.).NOTE 6If the illustrated device is used, the specimens are attached tothe specimen ring by contact cement.10. Operator Process Control10.1 Prepare four specimens of Standard U.S. Mesh Sieveto fit the test apparatus.10.2 Following Section 11 or Section 13, d
41、epending on themethod to be used for the geotextile specimens, perform testingon each mesh specimen.10.3 Based on an interlaboratory test, involving sevenlaboratories, the permittivity of No 200 Standard US MeshSieve material has been determined to be 5.00 s1, with astandard deviation of 0.65.10.3.1
42、 New operator process control shall be performeduntil it is demonstrated that the operator is proficient in testperformance as demonstrated by obtaining the value of per-mittivity stated in 10.3, plus or minus two standard deviations.10.3.2 Following initial proficiency testing, the operatorshall pe
43、rform process control testing on a semi-annual basis.CONSTANT HEAD TEST11. Procedure11.1 Assemble the apparatus with the specimen in place.11.2 Open the bleed valve and backfill the system throughthe standpipe or discharge pipe, with de-aired water. Backfill-ing in this manner forces any trapped air
44、 out of the system andthe geotextile.NOTE 7The water should be at the bottom level of the specimen at thetime of specimen installation.11.3 Close the bleed valve once water flows from it.Continue to fill the apparatus with de-aired water until thewater level reaches the overflow.11.4 With water flow
45、ing into the system through the waterinlet, adjust the discharge pipe along with the rate of waterflowing into the apparatus to obtain a 50-mm (2-in.) head ofwater on the geotextile. This is the head (h) under which thetest will be performed initially.11.5 Submerge a tube attached to a source of vac
46、uum to justabove (10 mm (0.5 in.) the surface of the geotextile, movingthe tube gently over the surface while applying a slight vacuumin order to remove any trapped air that may be in or on thespecimen. If necessary, readjust the head to 50 mm (2 in.) afterremoving the vacuum.11.6 Record the values
47、of time (t), quantity of flow (Q)ascollected from the discharge pipe, and water temperature (T),holding the head at 50 mm (2 in.). Make at least five readingsper specimen and determine an average value of permittivityfor the specimen.NOTE 8The quantity of flow may be measured in millilitres and then
48、converted to cubic millimetres for the computation of permittivity (1mL = 1000 mm3).11.7 After the first specimen has been tested under a 50-mm(2-in.) head, using the same specimen, start with a 10-mm(38-in.) head and repeat the procedure. Increase the head by 5mm (316 in.) after every five readings
49、. Increase the head untila 75-mm (3-in.) head is reached. Use this data to determine theregion of laminar flow. Plot volumetric flow rate, v, (where vequals Q/At, values defined in 12.1) versus head. The quantityof flow (Q) should be corrected to 20C (68F). The initialstraight line portion of the plot defines the region of laminarflow. If the 50-mm head is outside the region of laminar flow,repeat the test procedure using the head of water in themid-region of laminar flow.11.7.1 Compare the data from 10.7 with the apparatuscalibration curve referred
