1、Designation: D 6767 08Standard Test Method forPore Size Characteristics of Geotextiles by Capillary FlowTest1This standard is issued under the fixed designation D 6767; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the poresize distribution of geotextile filters with pore sizes rangingfrom
3、 1 to 500 m.NOTE 1The accuracy of this procedure has been verified up to amaximum pore size of 200 m. Above this value accuracy has been foundto be equipment dependent and should be verified by the user throughchecks on materials with known opening sizes.1.2 The test method measures the entire pore
4、size distribu-tion in terms of a surface analysis of specified pore sizes in ageotextile, defined in terms of the limiting diameters.1.3 The analyst should be aware that adequate collaborativedata for bias statements as required by Practice D 2777 is notprovided. See the precision and bias section f
5、or details.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard may involve hazardous materials, opera-tions, and equipment. This standard does not purport toaddress all of the safety concerns, if any, associate
6、d with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 2777 Practice for Determin
7、ation of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD 4354 Practice for Sampling of Geosynthetics for TestingD 4439 Terminology for Geosynthetics3. Terminology3.1 DefinitionsFor definitions of other terms used in thesetest methods, refer to Definitions D 4439 and D 1129.3.
8、2 Definitions of Terms Specific to This Standard:3.2.1 bubble point pore size (O98), nthe largest effectivepore diameter detected by the sudden increase of flow rate atthe beginning of the wet test.3.2.2 pore constriction (O), ndiameter of a circle havingthe same area as the smallest section of a gi
9、ven pore.3.2.3 pore size (Oi), ncapillary equivalent pore diameterfor which the percent of total pore diameters i in a givengeotextile based on the surface occupied by the pores aresmaller than or equal to that diameter.3.2.4 pore size distribution (PSD), npercent cumulativedistribution of the compl
10、ete range of pore sizes with in a givengeotextile based on the surface occupied by the pores.3.2.5 wetting liquid, nliquid used to submerge the geo-textile specimen prior to beginning the test.4. Summary of Test Method4.1 Geotextile filters have discrete pores from one side tothe other of the geotex
11、tile. The bubble point test is based on theprinciple that a wetting liquid is held in these continuous poresby capillary attraction and surface tension, and the minimumpressure required to force liquid from these pores is a functionof pore diameter.4.2 A fluid-wet geotextile will pass air when the a
12、pplied airpressure exceeds the capillary attraction of the fluid in the poreconstriction. Smaller pore constrictions will exhibit similarbehavior at higher pressures. The relationship between poresize and pressure has been established for water.1This test method is under the jurisdiction of ASTM Com
13、mittee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.03 on Perme-ability and Filtration.Current edition approved April 1, 2008. Published April 2008. Originallyapproved in 2002. Last previous edition approved in 2002 as D 676702.2For referenced ASTM standards, visit the AS
14、TM 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Unit
15、ed States.4.3 By comparing the gas flow rates of both a wet and drygeotextile at the same pressures, the percentage of the flowpassing through the filter pores larger than or equal to thespecified size may be calculated from the pressure-size rela-tionship. By increasing pressure in small steps, it
16、is possible todetermine the flow contribution of very small pore sizeincrements by difference.5. Significance and Use5.1 This test method may be used to:5.1.1 Determine the pore size distribution of a geotextile,5.1.2 Determine the maximum pore size of a geotextile,5.1.3 Determine the mean flow pore
17、 size of a geotextile,5.1.4 Determine the effect of processes such as calenderingor needle punching upon the pore size distribution,5.1.5 Determine the effect of compression upon the poresize distribution of a geotextile, and5.1.6 Determine the gas flow rate of a geotextile, andthereby its gas flow
18、capability.5.2 The pore size distribution test is significant not only forindicating pore sizes, but may also indicate a damaged,contaminated, or clogged geotextile.6. Apparatus36.1 Clean Gas Pressure Source, with regulation (filtered airor nitrogen).6.2 Pressure Transducer, U-tube Manometer or Gage
19、, (orset of gages), covering the necessary pressure range for thepore sizes under study (see Table 1).NOTE 2Pressure measurements must be installed immediately up-stream (for example, within 5 mm) of the sample holder.6.3 Closed Filter Holder, (see Fig. 1).NOTE 3The filter holder should be checked f
20、or leaks by placing ageomembrane in the holder and increasing the pressure to 70 kN/m2andholding it for a period of one minute.6.4 Metal Punch, used to cut a suitable size geotextile fromthe test sheet to fit the test filter holder.6.5 Set of Flowmeters, covering the range from 0 to 5000L/min.NOTE 4
21、Four flowmeters with flow rates of 0 to 0.4, 0 to 2.5, 0 to 25,and 0 to 100 L/min, placed in a parallel arrangement to cover the range offlow rates anticipated are recommended for geotextiles. The smallest flowrate that could be measured by the flowmeters is typically reported to be0.02 L/min. The m
22、anufacturer-rated precision of each flowmeter istypically reported to be 0.25 percent of the maximum reading.6.6 In-Line Fluid Trap, to protect the flowmeters from thefluid.6.7 Appropriate Fittings, Hose, Connectors, Piping,toas-semble apparatus as shown in Figs. 2 and 3.6.8 x-y Recorder, to assist
23、in graphing results of mean flowpore test.7. Sampling7.1 Lot SampleFor routine Quality Control testing, dividethe product into lots and take the lot sample as directed inPractice D 4354, Section 7 “Procedure B Sampling for QualityAssurance Testing.” For Specification Conformance testing,sample as di
24、rected in Practice D 4354, Section 6 “ProcedureA-Sampling for Specification Conformance.”7.2 Laboratory SampleAs a laboratory sample for accep-tance testing, take a full width swatch 1 m long from the endof each roll of fabric in the lot sample, after first discarding aminimum of1moffabric from the
25、very outside of the roll.7.3 Test SpecimensCut five specimens from each swatchin the laboratory sample with each specimen being cut to fit theappropriate sieve pan. Cut the specimens from a single swatchspaced along a diagonal line on the swatch.8. Specimen Preparation8.1 Weigh the specimens, submer
26、ge them in water for 1 h,and then allow the specimens to air dry at the standardatmosphere for testing. The specimen must be completely drybefore testing. Weigh the specimen after air drying until aconstant weight equal to or less than the initial weight of thespecimen is achieved. Air may be blown
27、over the specimenswith a fan to facilitate drying.9. Wetting Liquids9.1 Purity of ReagentsReagent grade chemicals shall beused for wetting liquids in all tests. Unless otherwise indicated,it is intended that all reagents shall conform to the specifica-tions of the Committee onAnalytical Reagents of
28、theAmericanChemical Society where such specifications are available.4Other grades may be used provided it is first ascertained thatthe reagent is of sufficient high purity to permit its use withoutlessening the accuracy of the determination.9.2 Water, conforming to Specification D 1193, Type IV orhi
29、gher purity.9.3 Denatured Alcohol.9.4 Petroleum Distillate, with surface tension of 30dynes/cm at 25C.9.5 Mineral Oil, such as USP liquid petrolatum heavy, withsurface tension of 34.7 dynes/cm at 25C.9.6 1,1,2-trichloro-1,2,2-trifluoret hane. (Freon TFt), avail-able from commercial chemical supply h
30、ouses.3Different equipment is available for obtaining pore size measurements includ-ing commercially available equipment from Porous Materials Inc. (PMI) (withspecial modifications for geotextiles) and Beckman Coulter, Inc. The equipmentdevelopers should be contacted for limitation specifically in r
31、elation to measuringthe larger opening sizes of geotextiles.4Reagent Chemicals, American Chemical Society Specifications, Am. ChemicalSoc., Washington, DC. For suggestions on the testing of reagents not listed by theAmerican Chemical Society, see “Reagent Chemicals and Standards,” by JosephRosin, D.
32、 Van Nostrand Co., Inc., New York, NY, and the “United StatesPharmacopeia.”TABLE 1 Pressure Ranges RequiredFluidUsedPore Size Range to be InvestigatedSurfaceTensiondynes/cmat 25C$ 100 m $ 50 m $ 10 m $ 1mWater 0 to 2.5 kPa 0 to 7.5 kPa 0 to 25 kPa 0 to 200 kPa 72Petroleumdistillate0 to 100 kPa 30Min
33、eraloil0 to 75 kPa 34.7D67670829.7 Clean Gas Pressure Source, with regulation (filtered airor nitrogen).NOTE 5Table 1 lists the nominal surface tension of these liquids at25C. There is a potential influence of the liquid on a measurement of poresize, which should be taken into account by users throu
34、gh verification testson materials with known pore size. Other liquids can be used and severalare currently under evaluation10. Procedure for One Holder (see Fig. 2)10.1 Place a dry geotextile sample disk in the geotextileholder.10.2 Close the holder and apply gas pressure in increments.10.3 Plot gas
35、 flow versus gas pressure over the intendedrange of use.10.4 Reduce gas pressure and remove the geotextile fromthe holder.10.5 Completely wet the geotextile by submerging it inwetting liquids (for example, water) for a period of 30 min.Replace the wet geotextile in the holder, and apply a slightpres
36、sure, checking to see that a tight seal exists. This pressuremust not exceed the bubble point pore size.FIG. 1 Closed Filter HolderFIG. 2 Setup for One HolderFIG. 3 Setup for Two HoldersD676708310.6 Plot the fluid-wet filter gas flow versus pressure on thesame coordinates as for the plot made in acc
37、ordance with 10.3.10.7 Reduce the pressure, remove the filter, and clean theholder for the next test.11. Procedure for Two Holders (see Fig. 3)11.1 Place a dry geotextile in the holder to be used exclu-sively for dry geotextiles.11.2 Wet a geotextile of the same type and lot as thegeotextile used in
38、 11.1, in reagent and place it in a holder to beused exclusively for wet geotextiles.11.3 Apply gas pressure to the dry geotextile and plot gasflow versus gas pressure.11.4 Change the two position valve to apply gas pressure tothe wet geotextile holder and record the first gas flow asdetected by the
39、 capillary tube as the bubble point. Switch toflowmeters and plot fluid-wet gas flow versus gas pressure.12. Calculation of Pore Size, Pore Size Distribution andFrequency12.1 The calculation of pore size is based on the equilibriumof forces as shown by Eq 1.p Oig B cosu5Sp4DO2P (1)where:Oi= pore siz
40、e, m,g = surface tension, mN/m, (dynes/cm),P = pressure, Pa or cm Hg, andB = capillary constant.The left-hand side of Eq 1 is the resisting force developedfrom surface tension acting between the liquid and the side-walls of a pore constriction of diameter O. The right-hand sideof Eq 1 is the driving
41、 force developed from the appliedpressure multiplied by the area of the pore constriction. Eq 2 isderived by rewriting Eq 1 to solve for O.O 54TB cosu!P(2)If the test liquid is known to wet the geotextile completely,and u = 0, then:O 5C gP(3)where:C = constant, 2860 when P is in Pa, 2.15 when P is i
42、n cmHg, and 0.415 when P is in psi units.NOTE 6If the contact angle is greater than zero, the calculatedeffective pore size will be larger than the actual effective pore size rating.12.2 Select the limits of the pore size range being evaluated.Substitute the limits individually into the pore-size ve
43、rsuspressure formula, obtain their respective pressures and plot theresults. From the test results, determine the wet and dry flowsat each pressure measured in the wet test and extrapolated fromthe dry curve over the pressure limits (pore size limits of therange) as shown in Fig. 4.12.3 The PSD of a
44、 geotextile is found by using Eq 4 at eachdifferent pressure and flow rate measured.% Finer 5F1 2wet flow rate!dry flow rate!G100! (4)NOTE 7Since the change in pore size per unit change in appliedpressure is greatest at large pore sizes and diminishes hyperbolically,repeatability and reproducibility
45、 increase accordingly with applied pres-sure.13. Report13.1 Report the geotextile identification, date and time oftest, and all pertinent general testing conditions.FIG. 4 Example of Pore Size Frequency DeterminationD676708413.2 Indicate in a table for each tested specimen: BubblePoint (O98) and val
46、ues (O95, O90, O85, O60, O30, O15, O10, O5).Indicate the mean values and the coefficient of variation foreach pore size.13.3 Provide a complete pore size distribution curve show-ing the pore size on the x-axis and percent finer than on they-axis as shown in the example in Fig. 5.14. Precision and Bi
47、as14.1 Results should not differ from the mean by more thanthe following amounts:Pore SizeRangeRepeatability, %Same Operatorand ApparatusReproducibility, %Different Operatorand ApparatusGreater than 100 m 2 410 to 100 m 1 2.5Pore SizeRangeRepeatability, %Same Operatorand ApparatusReproducibility, %D
48、ifferent Operatorand Apparatus1to10m 0.5 1FIG. 5 Typical Geotextile Pore Size Distribution CurveD6767085APPENDIXX1. PORE SIZE FORMULA DERIVATIONX1.1 The pore size formula is derived as follows:Surface tension formula:g5hpgr2 cos fbRearranging for diameter (2r):d 54 cos fBghpgAt bubble point pressure
49、 P = hgp:d 54 cos fBgPWhen a fluid wets a filter cos f =1:d 54 BgPwhere:h = height of rise,p = density of fluid,g = gravitational constant,r = radius of tube,f = contact angle,B = capillary Constant,5andg = surface tension.Substituting pressure conversion factors and the capillaryconstant:For centimetres of HG:d 52.145 g dynes/cm!#P cm Hg!#For psi:d 50.415 g dynes/cm!#P psi!#For Pa:d 52860 g dynes/cm!#P Pa!#ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin
