1、Designation: D6767 16Standard Test Method forPore Size Characteristics of Geotextiles by Capillary FlowTest1This standard is issued under the fixed designation D6767; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 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 1
3、 to 1000 m.NOTE 1The accuracy of this procedure has been verified up to amaximum pore size of 500 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 s
4、ize distribu-tion in terms of a surface analysis of specified pore sizes in ageotextile, defined in terms of the limiting diameters.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard may involve hazardous mate
5、rials,operations, and equipment. This standard does not purport toaddress all of the safety concerns, if any, associated 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 p
6、rior to use.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD4354 Practice for Sampling of Geosynthetics and RolledErosion Control Products(RECPs) for TestingD4439 Terminology for Geosynthetics3. Terminology3.1 DefinitionsFor definit
7、ions of other terms used in thistest method, refer to Terminologies D4439 and D1129.3.2 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 const
8、riction (O), ndiameter of a circle havingthe same area as the smallest section of a given 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 dia
9、meter.3.2.4 pore size distribution (PSD), npercent cumulativedistribution of the complete range of pore sizes with in a givengeotextile based on the surface occupied by the pores.3.2.5 wetting fluid, nfluid used to wet the geotextile testspecimen for the capillary porometry portion of the testmethod
10、, that is, the “wet” test. The verb “wet” is intended tomean to completely saturate the geotextile specimen with thewetting fluid thoroughly such that the entire thickness of thespecimen contains fluid with no entrained air bubbles.4. Summary of Test Method4.1 Geotextile filters have discrete pores
11、from one side tothe other of the geotextile. The bubble point test is based on theprinciple that a wetting fluid is held in these continuous poresby capillary attraction and surface tension, and the minimumpressure required to force fluid from these pores is a functionof pore diameter.4.2 A fluid-we
12、t geotextile will pass air when the applied 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 the wetting fluid.4.3 By
13、 comparing the gas flow rates of both a wet and drytest at the same pressures, the percentage of the flow passingthrough the filter pores larger than or equal to the specified sizemay be calculated from the pressure-size relationship. Byincreasing pressure in small steps, it is possible to determine
14、the flow contribution of very small pore size increments bydifference.1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.03 on Perme-ability and Filtration.Current edition approved Sept. 1, 2016. Published October 20
15、16. Originallyapproved in 2002. Last previous edition approved in 2014 as D6767 14. DOI:10.1520/D6767-16.2For 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 standar
16、ds Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. 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 maxi
17、mum pore size of a geotextile,5.1.3 Determine the mean flow pore size of a geotextile,5.1.4 Determine the effect of processes such as calendaringor needle punching upon the pore size distribution,5.1.5 Determine the effect of compression upon the poresize distribution of a geotextile, if the test eq
18、uipment allows,5.1.6 Determine the gas flow rate of a geotextile, andthereby its gas flow capability.5.2 The pore size distribution test may also be used forresearch, material development or to assess clogging onfield-retrieved samples.6. Apparatus6.1 Clean Gas Pressure Source, with regulation (filt
19、eredair).6.2 Pressure Sensor, pressure measurements may be ob-tained with a digital pressure transducer, a U-Tube manometeror an inclined manometer covering the necessary pressurerange for the pore sizes under study and the wetting fluid used.The pressure sensor sensitivity shall be dictated by the
20、range ofpressures associated with the openings sizes. The bubble pointpressure should be measured with an accuracy of 61% or65 Pa, whichever is larger.6.2.1 Pressure sensor(s) must be installed immediately up-stream (for example, within 5 mm) of the sample holder.6.3 Closed Filter Holder, (see Fig.
21、1).6.3.1 Filter holder for the test specimens that fully confinesthe perimeter of the specimen to prevent any lateral pressurelosses.6.3.2 The specimen flow area shall be 25-mm diameter.Other diameters shall be verified with comparative tests withthe standard 25-mm diameter.6.3.3 The filter holder s
22、hould 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 1 min. The flow rate measuredduring this period must be “zero.”6.4 Metal Punch, used to cut a suitable size geotextile fr
23、omthe test sheet to fit the test filter holder.6.5 Flow Rate Measurement Sensors, the porometer shouldbe equipped with sensors to measure the flow rate that are highenough to derive the desired pore size distribution. Themaximum flow rate measurement required will depend on theopening diameter and t
24、he dry air flow that corresponds to thesmallest opening that can be determined with this method onthe geotextile type under test. The minimum sensitivity, that is,the detection threshold, is dictated by the flow rate thatcorresponds to the onset of flow at the bubble point. For somegeotextiles, this
25、 value may be as low as 0.1 L/min.6.5.1 A series of floating ball-type flow meters placed in aparallel arrangement to cover the ranges of flow rates isacceptable provided the minimum and maximum flow ratemeasurements can be obtained with an accuracy of 5 % or lessof the measured value.6.5.2 Digital
26、flow meters are preferred for measurement offlow rates. Two or more digital flow meters of differentcapacities and sensitivities may be necessary to cover both theminimum detection value and the maximum dry specimenvalue. The accuracy of digital flow meters shall be 0.25 % ofthe maximum reading.6.6
27、In-Line Fluid Trap, for porometers which have the flowrate sensors downstream from the test specimen to protect theflow meters from being contaminated by the exhausted fluid.6.7 Appropriate Fittings, Hose, Connectors, Piping, to as-semble apparatus.6.8 Balance, with a precision of 0.001 g.7. Samplin
28、g7.1 Lot SampleFor routine Quality Control testing, dividethe product into lots and take the lot sample as directed inPractice D4354, Section 7 “Procedure B Sampling for QualityAssurance Testing.” For Specification Conformance testing,sample as directed in Practice D4354, Section 6 “ProcedureA-Sampl
29、ing 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 very outside of the roll.7.3 Test SpecimensCut five sp
30、ecimens from each swatchin the laboratory sample with each specimen being cut to fit theFIG. 1 Closed Filter HolderD6767 162appropriate sieve pan. Cut the specimens from a single swatchregularly spaced along a diagonal line on the swatch.8. Specimen Preparation8.1 Weigh the specimens previously cond
31、itioned at thestandard atmosphere for testing geosynthetics to 0.001 g.8.2 Submerge them in water for 1 h.8.3 Allow the specimens to air dry at the standard atmo-sphere for testing geosynthetics. The specimen must be com-pletely dry before testing. Weigh the specimen to 0.001 g afterair drying until
32、 a constant weight equal to or less than the initialweight of the specimen is achieved. Air may be blown over thespecimens with a fan to facilitate drying. Alternatively, condi-tion the specimens 24 h at the standard atmosphere for testinggeosynthetics.9. Wetting Fluids9.1 Purity of ReagentsReagent
33、grade chemicals shall beused for wetting fluids in all tests. Unless otherwise indicated,it is intended that all reagents shall conform to the specifica-tions of the Committee onAnalytical Reagents of theAmericanChemical Society where such specifications are available.3Other grades may be used provi
34、ded 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 D1193, Type IV orhigher purity.9.3 Wetting Fluid, the standard wetting fluid for this testmethod is Mineral Oil, USP li
35、quid petrolatum heavy, withsurface tension of 34.7 dynes/cm at 25C.9.3.1 Other wetting fluids may be used as a deviation fromthe standard. The user shall then verify the consistency of theresulting opening size distribution with the distribution ob-tained with Mineral Oil using comparative tests.9.4
36、 Clean Gas Pressure Source, with regulation (filteredair).10. Procedure10.1 Place a dry geotextile sample disk in the geotextileholder.10.2 Close the holder and apply gas pressure.10.2.1 The pressure shall first be increased from zero to apressure lower to, but close to the pressure associated with
37、thesmallest opening. No flow should be detected through thespecimen at this stage.10.2.2 The pressure shall then be increased at a constantrate. The rate at which the pressure is increased can affect theresulting opening distribution. The pressure ramp rate shouldbe slow enough not to produce a “rig
38、ht-shift” of the wet curve,that is, underestimate of the opening size. This should beconfirmed with consecutive tests using a single test specimentested at varying pressure ramp rates. Pressure and flow rateshall be recorded with an acquisition rate sufficient to capturethe requisite values.10.3 Plo
39、t the air flow rate versus 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 in thewetting fluid for a period of 1 h. Air bubbles should not beentrained in the wetting fluid.10.6 Increase the p
40、ressure using the same precautions re-garding the ramp rate and data acquisition rate described in10.2.2.10.7 Plot the fluid-wet filter gas flow versus pressure on thesame coordinates as for the plot made in accordance with 10.3.10.8 Reduce the pressure, remove the filter, and clean theholder for th
41、e next test.11. Calculation of Pore Size, Pore Size Distribution andFrequency11.1 The calculation of pore size is based on the equilibriumof forces as shown by Eq 1. Oi Bcos 5S4DO2P (1)where: = Pi, 3.1416Oi= pore size, m, = surface tension, mN/m, (dynes/cm),P = pressure, Pa or cm Hg, andB = capillar
42、y constant. = contact angleThe left-hand side of Eq 1 is the resisting force developedfrom surface tension acting between the fluid and the sidewallsof a pore constriction of diameter O. The right-hand side of Eq1 is the driving force developed from the applied pressuremultiplied by the area of the
43、pore constriction. Eq 2 is derivedby rewriting Eq 1 to solve for O.O 54TB cos !P(2)If the test fluid is known to wet the geotextile completely,and = 0, then:O 5C P(3)where:C = constant, 2860 when P is in Pa, 2.15 when P is in cmHg, and 0.415 when P is in psi units.11.2 Select the limits of the pore
44、size range being evaluated.Substitute the limits individually into the pore-size versuspressure 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
45、pressure limits (pore size limits of therange) as shown in Fig. 2.3Reagent 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 JosephRos
46、in, D. Van Nostrand Co., Inc., New York, NY, and the “United StatesPharmacopeia.”D6767 16311.3 The PSD of a geotextile is found by using Eq 4 at eachdifferent pressure and flow rate measured.% Finer 5F1 2wet flow rate!dry flow rate!G 100! (4)NOTE 2Since the change in pore size per unit change in app
47、liedpressure is greatest at large pore sizes and diminishes hyperbolically,repeatability and reproducibility increase accordingly with applied pres-sure.12. Report12.1 Report the geotextile identification, date and time oftest, and all pertinent general testing conditions.12.2 Indicate in a table fo
48、r each tested specimen: TheBubble Point (O98) and the pore size values at O95, O90, O85,O60, O50, O30, O15, O10, and O5. Indicate the mean values andthe coefficients of variation for each reported value.12.2.1 The character of the capillary porometry (wet) testshould be assessed to determine the sma
49、llest opening size thatcan be accurately determined with capillary theory. Often,especially when testing nonwoven geotextiles, the wet curvediverges from the threoretical porometry response and plotsparallel with the dry flow rate versus pressure curve beyond acertain pressure value, indicating an indeterminate regionwhere the opening sizes cannot be calculated. This response isrelated to the influence of “residual” wetting fluid in thespecimen matrix.12.3 Provide a complete pore size distribution curve show-ing the pore size on the x-axis and perce
