1、Designation: D 5493 06Standard Test Method forPermittivity of Geotextiles Under Load1This standard is issued under the fixed designation D 5493; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、 parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the waterpermittivity behavior of geotextiles in a direction normal to theplane of the geotextile
3、when subjected to specific normalcompressive loads.1.2 Use of this test method is limited to geotextiles. This testmethod is not intended for application with geotextile-relatedproducts such as geogrids, geonets, geomembranes, and othergeocomposites.1.3 The values stated in SI units are to be regard
4、ed as thestandard. The inch-pound units given in parentheses are forinformation only.1.4 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 an
5、d determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 123 Terminology Relating to Textile MaterialsD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 4354 Practice for Sampling of Geosynthetics for TestingD 4439 Terminology for
6、 GeosyntheticsD 4491 Test Method for Water Permeability of Geotextilesby PermittivityD 4716 Test Method for Determining the (in-plane) FlowRate per Unit Width and Hydraulic Transmissivity of aGeosynthetic Using a Constant HeadE11 Specification for Wire Cloth and Sieves for TestingPurposes3. Terminol
7、ogy3.1 Definitions:3.1.1 geotextile, nany permeable textile material usedwith foundation, soil, rock, earth, or any other geotechnicalengineering related material as an integral part of a manmadeproject, structure, or system (see Terminology D 4439).3.1.2 hydraulic gradient, i, nthe loss of hydrauli
8、c headper unit distance of flow, dh/dL (see Test Method D 4716).3.1.3 permittivity, (c), (T-1), nof geotextiles, the volumet-ric flow rate of water per unit cross-sectional area per unit headunder laminar flow conditions, in the normal direction througha geotextile (see Terminology D 4439).3.2 For t
9、he definitions of other terms relating to geotextiles,refer to Terminology D 4439. For the definitions of textileterms, refer to Terminology D 123. For the definitions ofcoefficient of permeability, refer to Terminology D 653.4. Summary of Test Method4.1 This test method provides a procedure for mea
10、suring thewater flow, in the normal direction through a known crosssection of a single layer of a geotextile at predeterminedconstant hydraulic heads over a range of applied normalcompressive stresses.4.2 The permittivity of a geotextile, c, can be determined bymeasuring the flow rate of water, in t
11、he normal direction,through a known cross section of a geotextile at predeterminedconstant water heads.4.3 Water flow through geotextiles can be laminar, transient,or turbulent, and therefore permittivity cannot be taken as aconstant.5. Significance and Use5.1 The thickness of a geotextile decreases
12、 with increase inthe normal compressive stress. This decrease in thickness mayresult in the partial closing or the opening of the voids ofgeotextile depending on its initial structure and the boundaryconditions.1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is
13、the direct responsibility of Subcommittee D35.03 on Perme-ability and Filtration.Current edition approved Jan. 1, 2006. Published January 2006. Originallyapproved in 1993. Last previous edition approved in 2003 as D 5493 93 (2003).2For referenced ASTM standards, visit the ASTM website, www.astm.org,
14、 orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 This test m
15、ethod measures the permittivity due to achange of void structure of a geotextile as a result of an appliedcompressive stress.6. Apparatus6.1 The apparatus is a constant head permeameter. Generalguidance on the hydraulic design of a constant head permeame-ter can be found in Test Method D 4491.6.2 Th
16、e components installed around the test specimen aredesigned in such a way that a normal load can be applieduniformly on the entire flow surface without restraining sig-nificantly the flow rate. The permittivity of the apparatus,calculated using the calibration curve established in section 10,shall b
17、e at least 10 times greater than the permittivity of the testspecimen under the hydraulic conditions prevailing during agiven test. However, the central deflection of the loadingmechanism on the plane of the geotextile shall not exceed0.025 mm while subjected to the maximum normal loadapplied during
18、 the test.6.3 The recommended apparatus configuration is shown inFig. 1:6.3.1 An optimum flow diameter has been found to be 50mm to minimize hydraulic side effects while ensuring anoptimum rigidity of the loading mechanism.6.3.2 A wire meshes, 1.0 mm in opening, complying withSpecification E11is ins
19、talled as the contact surface on bothsides of the test specimen.6.3.3 Two rigid metallic plate with the geometry shown onFigure 2 act as a structural component on both sides of the wiremeshes. The lower one is supported by the apparatus, while theupper one can move freely but is adjusted to the diam
20、eter of theflow channel.6.3.4 The upper metallic plate is connected to a devicecapable of applying the requested normal load on the testspecimen (dead loads, air piston or any suitable device). Themechanical connection between the upper metallic plate andthe loading mechanism consists of four rods,
21、3 mm in diameter,distributed on a circle approximately 30 mm in diameter.6.3.5 A dial indicator can be connected to the loadingmechanism to monitor the specimen thickness during the test.7. Sampling7.1 Lot SampleAs a lot sample for acceptance testing,take at random the number of rolls of geotextile
22、directed in anapplicable material specification and the supplier (for examplePractice D 4354) or other agreement between the purchaserand the supplier. Consider rolls of geotextile to be the primarysampling units. If the specification requires sampling duringmanufacture, select the rolls for the lot
23、 sample at uniformlyspaced time intervals throughout the production period.NOTE 1An 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
24、as to provide a sampling plan with a meaningfulproducers risk, consumers risk, acceptable quality level, and limitingquality level.7.2 Laboratory SampleConsider the units in the lotsample as the units in the laboratory sample. Take a sample thatwill exclude material from the outer wrap of the roll o
25、r theinner wrap around the core unless the sample is taken at theproduction site, at which point the inner and outer wrapmaterial may be used.8. Test Water Preparation8.1 De-air the test water to provide reproducible test results.8.2 De-air the water used for saturation.FIG. 1 Specimen Holder and Lo
26、ading MechanismD54930628.3 De-air the water under a vacuum of 710 mm (28 in.) ofmercury (Hg) for the period of time to bring the dissolvedoxygen content down to a maximum of 6 ppm.8.4 Use dissolved oxygen meter or commercially availablechemical kits to determine the dissolved oxygen content.8.5 The
27、deaired system may be a commercially availablesystem, or one consisting of a vacuum pump capable ofremoving a minimum of 150 L/min of air in connection with anon-collapsible storage tank with a large enough storagecapacity for the test series, or at least one specimen at a time.Allow the deaired wat
28、er to stand in closed storage under aslight vacuum until room temperature is attained.8.6 If water temperature other than 20C is being used,make a temperature correction to the resulting value ofpermittivity.8.7 Determine the temperature correction factor using thefollowing equation:Rt 5 ut / u20 (1
29、)where:ut = water viscosity at test temperature, mP, as deter-mined from Table 1, andu20 = water viscosity at 20C, mP.9. Specimen Preparation9.1 Prepare four specimens of the geotextile to be testedavoiding sampling along the edges of the geotextile roll toensure homogeneity of the specimens.9.2 The
30、 minimum specimen diameter is 50 mm.9.3 Referring to Fig. 2, select the specimens, A, B, C, and Das follows:9.3.1 Take Specimen A at the center of the sample, B at onecorner (center located 200 mm from the corner), C midwaybetweenAand B, and D the same distance fromAas C, locatedon a line with A, B,
31、 and C.9.3.2 Cut specimens shall fit the testing apparatus.10. Calibrations10.1 Hydraulic Calibration:10.1.1 Run at least 3 tests without any geotextile specimeninstalled in the apparatus, each of them being ran with thesystem set to apply different normal loads spread over theequipment capability (
32、that is, 2, 20, and 200 kPa). Thespecimen shall be replaced by a rigid material approximately25 to 30 mm in diameter that will not restrain the flow (such asa 1 to 2 mm long section of a thick 25 mm PVC plastic pipe).For each test, measure the water heads corresponding to at least10 different flow r
33、ates uniformly spread between 0 and theequipment capability.10.1.2 Draw the Water Head versus Flow Rate curve andcalculate the intrinsic permittivity of the apparatus for eachflow rate using Eq 2. Plot both curves on the same graph asshown on Fig. 2.10.2 Normal Load CalibrationUse a convenient syste
34、mto control the precision of the normal load applied on thegeotextile. The normal load effectively applied shall be within5 % of the targeted load.10.3 Thickness Measurement CalibrationAlthough thick-ness measurement is not a mandatory requirement, if thethickness of the material is monitored, it sh
35、all be calibratedfirst. In that case, the central deflection requirement expressedin 6.2 shall be verified using the procedure presented below.10.3.1 Install a metallic ring 50 mm in diameter (or the innerdiameter of the flow channel), witha1mmwall and 10 mmthick in the sample holder in place of the
36、 geotextile.10.3.2 Apply the minimum load that can be achieved withthe equipment (that is, 2 kPa) and record the value provided bythe dial indicator as the zero for calibration purposes.10.3.3 Apply by increments 10 different normal loads uni-formly spread over the apparatus capability and record th
37、ecorresponding values given by the dial indicator.10.3.4 Plot the thickness versus load curve and verify thatthe deflection measured under 2, 20, and 200 kPa normal loadare less than 0.025 mm.TABLE 1 Viscosity of Water Versus TemperatureTemperature, C Viscosity (Poiseuille)A0 1.7921 3 10-61 1.7313 3
38、 10-62 1.6278 3 10-63 1.6191 3 10-64 1.5674 3 10-65 1.5188 3 10-66 1.4728 3 10-67 1.4284 3 10-68 1.3860 3 10-69 1.3462 3 10-610 1.3077 3 10-611 1.2713 3 10-612 1.2363 3 10-613 1.2028 3 10-614 1.1709 3 10-615 1.1404 3 10-616 1.1111 3 10-617 1.0828 3 10-618 1.0559 3 10-619 1.0299 3 10-620 1.0050 3 10-
39、621 0.9810 3 10-622 0.9579 3 10-623 0.9358 3 10-624 0.9142 3 10-625 0.8937 3 10-6APoiseuille = kg s-1m-1= Nsm.FIG. 2 Hydraulic Calibration CurveD549306311. Test Procedure11.1 Soak the specimen in a vessel containing deaired water,at room conditions, for a period of at least2htoensuresaturation and w
40、etting.11.2 Maintain the test specimen, underwater at all timesprior to and during the test.11.3 Allow the deaired water to flow from the bottom of theapparatus to the predetermined overflow located on the top ofthe upper section of the water tank using the drain tube as thewater inlet.11.4 Place th
41、e geotextile specimen in the apparatus insequence as shown in Fig. 1.11.5 Lower the piston until it reaches the upper metallicplate.11.6 Apply a load equal to 2 kPa.NOTE 2Unless otherwise specified, the permittivity shall be measuredunder 2, 20, and 200 kPa. If a different normal load is required, t
42、he firstapplied normal load shall be the lightest one.11.7 Continue to fill the tank from the outlet until the waterlevel reaches the outlet level. This step is needed to flush outany air bubbles located in the upper plate and the upper sectionof the cylinder. Air bubbles in the system may lead toer
43、roneous and non-reproducible test results.11.8 Connect the water line to the inlet reservoir to run thetest.11.9 The seating period shall be long enough to reach athickness variation of less than 0.0025 mm per minute.11.10 Measure the flow rate under total (uncorrected) hy-draulic heads of approxima
44、tely 15, 25, 50, and 75 mm, or morein order to apply an actual (corrected) hydraulic head in therange of 10 to at least 50 mm. Conduct three flow ratemeasurements for each water head and verify that the differ-ence between the lower and the higher value is less than 5 %.11.11 Increase the normal loa
45、d to reach the next requestednormal load and repeat the flow measurements as described in11.10.11.12 Repeat steps 11.9 to 11.11 for three additional testspecimens.NOTE 3If a reduction of permittivity is observed for a given product,it could be either caused by the products behavior (sensitivity to t
46、henormal load) or by air clogging during the test. The following procedurecan be used to assess whether air clogging has influenced the result or not:(1) apply a single normal load on the specimen; (2) measure itspermittivity; (3) let the water flow through the specimen for a period oftime equivalen
47、t to the total duration of the test, varying the water head insuch a way that the hydraulic head history of the actual test will bereproduced; (4) repeat the permittivity measurement; and (5) compare thedeviation between the two permittivity measurements.12. Calculation12.1 Use the calibration curve
48、 built in 10.1 to determine thewater head correction DHQ to be considered for each indi-vidual flow rate measurement.NOTE 4A power regression built with the values measured in 10.1usually provides a very good tool to automate the water head correction.12.2 Calculate the permittivity for each individ
49、ual measure-ments using Eq 2.c5Q 3 Rt/ SDH DHQ!# (2)where:Q = measured flow rate (Q = V / t, where V = volumeand t = time),Rt= temperature correction factor,S = flow surface,DH = measured water head, andDHQ= water head correction.12.3 Plot the permittivity versus the corrected water headfor each individual test specimen and determine the permittiv-ity in the laminar region, which is constant up to a certain waterhead.12.4 Determine the permittivity under a 50 mm water headusing a best fit curve and reading the value corresponding to a50 mm water head.12.5 C
