ASTM D7178-22

Standard Practice for Determining the Number of Constrictions “<emph type="ital" >m</emph>” of Non-Woven Geotextiles

SIGNIFICANCE AND USE
5.1 This practice provides a calculation method for determining the number of constrictions m of a non-woven geotextile (or of a layer of a composite material). This standard is not applicable to woven geotextiles, knitted geotextiles, heat-bonded geotextiles, or any other type of geosynthetic.  
5.2 The number of constrictions represents the number of “windows” delimited by three or more fibers, in which soil particles could migrate. This value has been found to be relevant to explain the different filtration behaviors of non-woven geotextiles with similar opening sizes but different structures for various soil conditions (see Appendix X1 for details).  
5.3 This value will be used in filtration research to evaluate the prediction of filtration efficiency and effectiveness of various non-woven geotextiles with similar opening sizes (Test Method D6767).  
5.4 Interpretation of the significance of m as calculated using this standard shall be done with care, as some non-woven structures may not reflect the hypothesis used to establish the proposed equation (see Appendix X1 for details).
SCOPE
1.1 This practice describes the procedure used along with existing test methods to determine the number of constrictions m of mechanically bonded non-woven geotextiles, based on thickness, mass per unit area, and fiber properties  
1.2 The number of constrictions is a property of non-woven geotextiles, which is complementary to opening size to predict their filtration behavior. It can be used to differentiate non-woven geotextiles with similar opening sizes but different structures (thickness, weight, fiber diameter, etc.). However, more research is needed to assess its significance when comparing two products with different opening sizes.  
1.3 Consideration of the number of constrictions is relevant in filtration applications where piping or clogging concerns are to be controlled with a high level of confidence, that is, for filter applications in critical soils.  
1.4 This standard is for design purposes only and is not intended for quality control purposes.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Nov-2022
• ICS: 59.080.70 - Geotextiles
• Technical Committee: D35 - Geosynthetics
• Drafting Committee: D35.03 - Permeability and Filtration

Relations

• Refers: ASTM D4751-20 - Standard Test Methods for Determining Apparent Opening Size of a Geotextile
• Effective Date: 01-Jan-2020

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7178 − 22
Standard Practice for
Determining the Number of Constrictions “m” of Non-Woven
1
Geotextiles
This standard is issued under the fixed designation D7178; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2
2.1 ASTM Standards:
1.1 This practice describes the procedure used along with
D1577 Test Methods for Linear Density of Textile Fibers
existing test methods to determine the number of constrictions
D4439 Terminology for Geosynthetics
m of mechanically bonded non-woven geotextiles, based on
D4751 Test Methods for Determining Apparent Opening
thickness, mass per unit area, and fiber properties
Size of a Geotextile
1.2 The number of constrictions is a property of non-woven
D5199 Test Method for Measuring the Nominal Thickness
geotextiles, which is complementary to opening size to predict
of Geosynthetics
their filtration behavior. It can be used to differentiate non-
D5261 Test Method for Measuring Mass per Unit Area of
woven geotextiles with similar opening sizes but different Geotextiles
structures (thickness, weight, fiber diameter, etc.). However, D6767 Test Method for Pore Size Characteristics of Geotex-
tiles by Capillary Flow Test
more research is needed to assess its significance when
comparing two products with different opening sizes.
3. Terminology
1.3 Consideration of the number of constrictions is relevant
3.1 Definitions—For definitions of terms used in this
in filtration applications where piping or clogging concerns are
practice, refer to Terminology D4439.
to be controlled with a high level of confidence, that is, for
3.2 Definitions of Terms Specific to This Standard:
filter applications in critical soils.
3.2.1 constriction, n—in the non-woven geotextile, a “win-
1.4 This standard is for design purposes only and is not
dow” delimited by three or more fibers, through which soil
intended for quality control purposes.
particles could migrate.
1.5 This standard does not purport to address all of the 3.2.2 fiber count, T, n—ameasureofthelineardensityofthe
–6
safety concerns, if any, associated with its use. It is the fiber expressed in tex, where 1 tex = 10 kg/m.
responsibility of the user of this standard to establish appro- 3.2.2.1 Discussion—The fiber count is sometime expressed
priate safety, health, and environmental practices and deter- in “Denier” (equivalent to the weight in grams of a theoretical
9000 mlongfiber).Thevaluein“tex”canbeobtainedfromthe
mine the applicability of regulatory limitations prior to use.
value in Denier considering that 1 Denier = 9 tex.
1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard- 3.2.3 filtration paths, n—under the forces induced by fluid
ization established in the Decision on Principles for the flows, soil particles may travel in the geotextile filter along
filtration paths. Each of these paths is composed of a sequence
Development of International Standards, Guides and Recom-
of constrictions of various size and shape.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
3.2.4 number of constrictions, m, n—average number of
constrictions for a filtration path.
3.2.5 opening size, n—largest significant opening of a non-
woven geotextile as measured using Test Method D6767.
3.2.5.1 Discussion—Although Test Method D4751 (Appar-
ent Opening Size) is widely used to characterize geotextiles, it
1
This practice is under the jurisdiction of ASTM Committee D35 on Geosyn-
thetics and is the direct responsibility of Subcommittee D35.03 on Permeability and
2
Filtration. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 1, 2022. Published December 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ɛ1
published in 2006. Last previous version approved in 2016 as D7178 – 16 . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D7178-22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7178 − 22
may often not be sufficient for advanced filtration investiga- respective percentages of polypropylene / xx tex, polypropyl-
tions such as those requiring consideration of the number of ene / yy tex, polyest
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D7178 − 16 D7178 − 22
Standard Practice for
Determining the Number of Constrictions “m” of Non-Woven
1
Geotextiles as a Complementary Filtration Property
This standard is issued under the fixed designation D7178; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1
ε NOTE—A legend was added editorially to Eq X1.4 in X1.1.2.2 in July 2016.
1. Scope
1.1 This practice describes the procedure used along with existing test methodmethods to determine the number of constrictions
m of mechanically bonded non-woven geotextiles, based on thickness, mass per unit area, and fiber properties
1.2 The number of constrictions is a property of non-woven geotextiles, which is complementary to opening size to predict their
filtration behavior. It can be used to differentiate non-woven geotextiles with similar opening sizes but different structures
(thickness, weight, fiber diameter, etc.). However, more research is needed to assess its significance when comparing two products
with different opening sizes.
1.3 Consideration of the number of constrictionconstrictions is relevant in filtration applications where piping or clogging
concerns are to be controlled with a high level of confidence, that is, for filtersfilter applications in critical soils.
1.4 This standard is for design purposes only and is not intended for quality control purposes.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
D1577 Test Methods for Linear Density of Textile Fibers
D4439 Terminology for Geosynthetics
D4751 Test Methods for Determining Apparent Opening Size of a Geotextile
D5199 Test Method for Measuring the Nominal Thickness of Geosynthetics
D5261 Test Method for Measuring Mass per Unit Area of Geotextiles
D6767 Test Method for Pore Size Characteristics of Geotextiles by Capillary Flow Test
1
This practice is under the jurisdiction of ASTM Committee D35 on Geosynthetics and is the direct responsibility of Subcommittee D35.03 on Permeability and Filtration.
Current edition approved June 1, 2016Dec. 1, 2022. Published June 2016December 2022. Originally published in 2006. Last previous version approved 2011 in 2016 as
ɛ1
D7178 – 06 (2011).D7178 – 16 . DOI: 10.1520/D7178-16E01.10.1520/D7178-22.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7178 − 22
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, practice, refer to Terminology D4439.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 constriction—constriction, n—in the non-woven geotextile, a “window” delimited by three or more fibers, through which
soil particles could migrate.
–6
3.2.2 fiber count, T, n—a measure of the linear density of the fiber expressed in tex, where 1 tex = 10 kg/m.
3.2.2.1 Discussion—
The fiber count is sometime expressed in “Denier” (equivalent to the weight in grams of a theoretical 9000 m long fiber). The value
in “tex” can be obtained from the value in Denier considering that 1 Denier = 9 tex.
3.2.3 filtration paths—paths, n—under the forces induced by fluid flows, soil particles may travel in the geotextile filter along
filtration paths. Each of these paths is composed of a sequence of constrictions of various size and shape.
3.2.4 number of constrictions, m—m, n—average number of constrictions for a filtration path.
-6
3.2.4 fiber count, T—a measure of the linear de
...