1、Designation: D4491 99a (Reapproved 2014)1Standard Test Methods forWater Permeability of Geotextiles by Permittivity1This standard is issued under the fixed designation D4491; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript 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.1NOTEEditorial changes were made through
3、out in February 2014.1. 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 falling
4、 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 user
5、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:2D123 Terminology Relating to TextilesD653 Terminology Relating to Soil, Rock, and ContainedFluidsD4439 Terminology
6、 for GeosyntheticsD5199 Test Method for Measuring the Nominal Thicknessof GeosyntheticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ASTM Adjuncts:3Detailed Drawings and Materials List for Construction, 10Drawings3. Terminology3.1 Definitions:3.1
7、.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 mechanics, and man
8、y 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 thickness is us
9、ed 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, (), (T1), nof geotextiles, the volu-metric
10、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 togeotextiles, refer to Terminology D4439. For the definitions oftextile terms, refer to Terminology D123. For th
11、e definition ofcoefficient of permeability, refer to Terminology D653.4. 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 of 50 mm (2 in.) of w
12、ateris 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 head test.1These test met
13、hods are under the jurisdiction of ASTM Committee D35 onGeosynthetics and are the direct responsibility of Subcommittee D35.03 onPermeability and Filtration.Current edition approved Jan. 1, 2014. Published February 2014. Originallyapproved in 1985. Last previous edition approved in 2009 as D4491 99a
14、(2009).DOI: 10.1520/D4491-99AR14E01.2For 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 page onthe ASTM website.3Detailed drawings and a
15、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. United States1NOTE 1Data has shown agreement between the falling and constanthead methods
16、of determining permittivity 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
17、of water through thegeotextile 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
18、 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. Competentstatist
19、ical 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 toeach laborato
20、ry 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 purchaser and thesu
21、pplier must agree to interpret 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, c
22、are shouldbe taken when 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 signifi
23、cant toevaluate the quantity 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
24、engineering, may be computed. By multiplyingpermittivity 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 te
25、st, thereby making it difficult 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 a
26、pparatus must be capable 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 w
27、ith 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. Thegeotextile specimen is positioned in the bottom of the upperunit. There is a standpipe for me
28、asuring the constant headvalue. 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
29、. For the device shown 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, takeat random
30、the number of rolls of 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 un
31、iformly spaced time intervals 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
32、 a sampling plan with a 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 c
33、an be met. Take a sample 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 w
34、ater shallbe de-aired under 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
35、 5The de-airing system may be either a commercially availablesystem or one consisting of a vacuum pump capable of removing a4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D35-1007. ContactASTM CustomerService at serviceastm.org
36、.D4491 99a (2014)12minimum 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.8.2 Allow the de-aired water to stand in a closed storagetank under a slight vacuum until room temperature is at
37、tained.9. Specimen Preparation9.1 To obtain a representative value of permittivity, takefour specimens from each full width laboratory sample asdescribed below.FIG. 1 Constant and Falling Head Permeability ApparatusD4491 99a (2014)139.2 Referring to Fig. 2, select four specimens, A, B, C, andD, as f
38、ollows: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 the corner of the laboratory sample than200 mm (8 in.).9.2.2 Take specimen A at the center
39、 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.9.2.3 Cut specimens shall fit the testing apparatus, forexample, 73 mm (2.87 in.) in diameter for the device illustratedin F
40、ig. 1.9.3 Condition the specimen by soaking in a closed containerof de-aired water, at room conditions, for a period of 2 h. Theminimum 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 Proc
41、ess Control10.1 Prepare four specimens of Standard U.S. Mesh Sieveto fit the test apparatus.10.2 Following Section 11 or Section 13, depending on themethod to be used for the geotextile specimens, perform testingon each mesh specimen.10.3 Based on an interlaboratory test, involving sevenlaboratories
42、, 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 New operator process control shall be performeduntil it is demonstrated that the operator is proficient in testperformance as demonstrated by obtaining the value of
43、per-mittivity stated in 10.3, plus or minus two standard deviations.10.3.2 Following initial proficiency testing, the operatorshall perform 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 a
44、nd backfill the system throughthe standpipe or discharge pipe, with de-aired water. Backfill-ing in this manner forces any trapped air 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
45、 water flows from it.Continue to fill the apparatus with de-aired water until thewater level reaches the overflow.11.4 With water flowing 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
46、 the geotextile. This is the head (h) under which thetest will be performed initially.11.5 Submerge a tube attached to a source of vacuum 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 a
47、ir 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 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 spe
48、cimen and determine an average value of permittivityfor the specimen.NOTE 8The quantity of flow may be measured in millilitres and thenconverted 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 th
49、e 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. 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, (wherevequals 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 proce
