ASTM_D_7178_-_16e1.pdf

Designation:D7178161Standard Practice forDetermining the Number of Constrictions“m”of Non-Woven Geotextiles as a Complementary Filtration Property1This standard is issued under the fixed designation D7178;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 parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1NOTEA legend was added editorially to Eq X1.4 in X1.1.2.2 in July 2016.1.Scope1.1 This practice describes the procedure used along withexisting test method to determine the number of constrictionsm of mechanically bonded non-woven geotextiles,based onthickness,mass per unit area and fiber properties1.2 The number of constrictions is a property of non-wovengeotextiles,which is complementary to opening size to predicttheir filtration behavior.It can be used to differentiate non-woven geotextiles with similar opening sizes but differentstructures(thickness,weight,fiber diameter,etc.).However,more research is needed to assess its significance whencomparing two products with different opening sizes.1.3 Consideration of the number of constriction is relevantin filtration applications where piping or clogging concerns areto be controlled with a high level of confidence,that is,forfilters applications in critical soils.1.4 This standard is for design purposes only and is notintended for quality control purposes.1.5 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.Referenced Documents2.1 ASTM Standards:2D1577 Test Methods for Linear Density of Textile FibersD4439 Terminology for GeosyntheticsD4751 Test Method for DeterminingApparent Opening Sizeof a GeotextileD5199 Test Method for Measuring the Nominal Thicknessof GeosyntheticsD5261 Test Method for Measuring Mass per Unit Area ofGeotextilesD6767 Test Method for Pore Size Characteristics of Geotex-tiles by Capillary Flow Test3.Terminology3.1 DefinitionsFor definitions of terms used in this testmethod,refer to Terminology D4439.3.2 Definitions of Terms Specific to This Standard:3.2.1 constrictionin the non-woven geotextile,a“win-dow”delimited by three or more fibers,through which soilparticles could migrate.3.2.2 filtration pathsunder the forces induced by fluidflows,soil particles may travel in the geotextile filter alongfiltration paths.Each of these paths is composed of a sequenceof constrictions of various size and shape.3.2.3 number of constrictions,maverage number of con-strictions for a filtration path.3.2.4 fiber count,Ta measure of the linear density of thefiber expressed in tex,where 1 tex=10-6kg/m.3.2.4.1 DiscussionThe fiber count is sometime expressedin“Denier”(equivalent to the weight in grams of a theoretical9000 meters long fiber).The value in“Tex”can be obtainedfrom the value in Denier considering that 1 Denier=9 Tex.3.2.5 opening sizelargest significant opening of a non-woven geotextile as measured using Test Method D6767.NOTE1Although Test Method D4751(Apparent Opening Size)iswidely used to characterize geotextiles,it may often not be sufficient foradvanced filtration investigations such as those requiring consideration ofthe number of constriction as a significant parameter.The“bubble-point”measurement technique proposed in Test Method D6767 shall thus bepreferred to AOS per Test Method D4751.4.Summary of Practice4.1 The physical properties of the geotextile are evaluatedaccording to specific procedures and the number of constrictionm is determined based on Eq 1.1This practice is under the jurisdiction of ASTM Committee D35 on Geosyn-thetics and is the direct responsibility of Subcommittee D35.03 on Permeability andFiltration.Current edition approved June 1,2016.Published June 2016.Originallypublished 2006.Last previous version approved 2011 as D7178 06(2011).DOI:10.1520/D7178-16E01.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Significance and Use5.1 This practice provides a calculation method for deter-mining the number of constrictions m of a non-woven geotex-tile(or of a layer of a composite material).This standard is notapplicable to woven geotextiles,knitted geotextiles,heat-bonded geotextiles or any other type of geosynthetic.5.2 The number of constriction represents the number of“windows”delimited by three or more fibers,in which soilparticles could migrate.In that regard,it can be basicallydefined by the following equation:m5tdcwh