1、Designation:D4491/D4491M15Standard Test Methods forWater Permeability of Geotextiles by Permittivity1This standard is issued under the fixed designation D4491/D4491M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last re
2、vision.A number in parentheses indicates the year of lastreapproval.A superscript 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.1.Scope1.1 These test methods cover procedures for deter
3、miningthe hydraulic conductivity(water permeability)of geotextilesin terms of permittivity under standard testing conditions,inthe uncompressed state.Included are three procedures:theconstant head and falling head methods using a water flowapparatus,and the air flow method using an air flow apparatu
4、s.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith th
5、e standard.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 of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Refer
6、enced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD653 Terminology Relating to Soil,Rock,and ContainedFluidsD4439 Terminology for GeosyntheticsD5199 Test Method for Measuring the Nominal Thicknessof GeosyntheticsE691 Practice for Conducting an Interlaboratory Study toDetermine
7、the Precision of a Test Method2.2 ASTM Adjuncts:3Detailed Drawings and Materials List for Construction,10Drawings3.Terminology3.1 Definitions:3.1.1 geotextile,na permeable geosynthetic comprisedsolely of textiles.3.1.2 permeability,nthe rate of flow of a liquid under adifferential pressure through a
8、 material.3.1.2.1 DiscussionThe nominal 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.3.1.3 permeability,nof geotextiles,hydraulic conductiv-ity.3.1.4 permi
9、ttivity,(),(T1),nof geotextiles,the volu-metric flow rate of water per unit cross sectional area per unithead under laminar flow conditions,in the normal directionthrough a geotextile.3.1.5 For the definitions of other terms relating togeotextiles,refer to Terminology D4439.For the definitions oftex
10、tile terms,refer to Terminology D123.For the definition ofcoefficient of permeability,refer to Terminology D653.4.Summary of Test Method4.1 Water Flow Test MethodsThese test methods describeprocedures for determining the permittivity of geotextiles usingconstant head or falling head test procedures
11、with a water flowapparatus:4.1.1 Method A-Constant Head TestA head of 50 mm ofwater is 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 obta
12、in readings of head change1These 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 July 1,2015.Published July 2015.Originally approvedin 1985.Last previous edit
13、ion approved in 2014 as D4491 99a(2014)1.DOI:10.1520/D4491_D4491M-15.2For 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 websi
14、te.3Detailed drawings and a 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 States1 versus time in the falling head test.The constant head
15、 test is thereferee method for this standard.NOTE1Data has shown agreement between the falling and constanthead methods 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 Method B-Falling Head Te
16、stA column of water isallowed to flow through the geotextile and readings of headchanges versus time are taken.The flow rate of water throughthe geotextile must be slow enough to obtain accurate readings.4.1.3 Method C-Air Flow TestA geotextile specimen issubjected to increasing air flow while the flow rate anddifferential pressure are measured.Two flow rate data pointsare obtained at pressures of 250 and 500 Pascals,which areused to determine the Characteristic Flow Equation of thespecimen.The
