ASTM D7178-06
(Practice)Standard Practice for Determining the Number of Constrictions "m" of Non-Woven Geotextiles as a Complementary Filtration Property
Standard Practice for Determining the Number of Constrictions "<bdit>m</bdit>" of Non-Woven Geotextiles as a Complementary Filtration Property
SIGNIFICANCE AND USE
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.
The number of constriction represents the number of “windows” delimited by three or more fibers, in which soil particles could migrate. In that regard, it can be basically defined by the following equation: where t is the thickness and dc the average distance between two constrictions. 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).
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 D 6767).
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 method 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 constriction is relevant in filtration applications where piping or clogging concerns are to be controlled with a high level of confidence, that is, for filters applications in critical soils.
1.4 This standard is for design purposes only and is not intended for quality control purposes.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: D7178 – 06
Standard Practice for
Determining the Number of Constrictions “m” of Non-
Woven 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. Scope D5261 Test Method for Measuring Mass per Unit Area of
Geotextiles
1.1 This practice describes the procedure used along with
D6767 Test Method for Pore Size Characteristics of Geo-
existing test method to determine the number of constrictions
textiles by Capillary Flow Test
m of mechanically bonded non-woven geotextiles, based on
thickness, mass per unit area and fiber properties
3. Terminology
1.2 The number of constrictions is a property of non-woven
3.1 Definitions—For definitions of terms used in this test
geotextiles, which is complementary to opening size to predict
method, refer to Terminology D4439.
their filtration behavior. It can be used to differentiate non-
3.2 Definitions of Terms Specific to This Standard:
woven geotextiles with similar opening sizes but different
3.2.1 constriction—in the non-woven geotextile, a “win-
structures (thickness, weight, fiber diameter, etc.). However,
dow” delimited by three or more fibers, through which soil
more research is needed to assess its significance when
particles could migrate.
comparing two products with different opening sizes.
3.2.2 filtration paths—under the forces induced by fluid
1.3 Consideration of the number of constriction is relevant
flows, soil particles may travel in the geotextile filter along
in filtration applications where piping or clogging concerns are
filtration paths. Each of these paths is composed of a sequence
to be controlled with a high level of confidence, that is, for
of constrictions of various size and shape.
filters applications in critical soils.
3.2.3 number of constrictions, m—average number of con-
1.4 This standard is for design purposes only and is not
strictions for a filtration path.
intended for quality control purposes.
3.2.4 fiber count, T—a measure of the linear density of the
1.5 This standard does not purport to address all of the
-6
fiber expressed in tex, where 1 tex = 10 kg/m.
safety concerns, if any, associated with its use. It is the
3.2.4.1 Discussion—The fiber count is sometime expressed
responsibility of the user of this standard to establish appro-
in “Denier” (equivalent to the weight in grams of a theoretical
priate safety and health practices and determine the applica-
9000 meters long fiber). The value in “Tex” can be obtained
bility of regulatory limitations prior to use.
from the value in Denier considering that 1 Tex = 9 Denier.
2. Referenced Documents 3.2.5 opening size—largest significant opening of a non-
2 woven geotextile as measured using Test Method D6767.
2.1 ASTM Standards:
D1577 Test Methods for Linear Density of Textile Fibers
NOTE 1—Although Test Method D4751 (Apparent Opening Size) is
D4439 Terminology for Geosynthetics
widely used to characterize geotextiles, it may often not be sufficient for
advanced filtration investigations such as those requiring consideration of
D4751 Test Method for Determining Apparent Opening
the number of constriction as a significant parameter. The “bubble-point”
Size of a Geotextile
measurement technique proposed in Test Method D6767 shall thus be
D5199 Test Method for Measuring the Nominal Thickness
preferred to AOS per Test Method D4751.
of Geosynthetics
4. Summary of Practice
4.1 The physical properties of the geotextile are evaluated
This practice is under the jurisdiction of ASTM Committee D35 on Geosyn-
accordingtospecificproceduresandthenumberofconstriction
thetics and is the direct responsibility of Subcommittee D35.03 on Permeability and
m is determined based on Eq 1.
Filtration.
Current edition approved June 1, 2006. Published July 2006. DOI: 10.1520/
5. Significance and Use
D7178-06.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.1 This practice provides a calculation method for deter-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
mining the number of constrictions m of a non-woven geotex-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. tile (or of a layer of a composite material). This standard is not
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7178 – 06
applicable to woven geotextiles, knitted geotextiles, heat-
1 1
m 5 3 p · µ · t 3 p · (1)
= Œ
i i i ( k
2 T
bonded geotextiles or any other type of geosynthetic.
k k
5.2 The number of constriction represents the number of
where:
“windows” delimited by three or more fibers, in which soil
i = specimen number,
particles could migrate. In that regard, it can be basically
m = number of constriction for the geotextile specimen i,
i
defined by the following equation: m 5 t d where t is the
c
/
µ = mass per unit area of the geotextile specimen i (g/m )
i
thickness and d the average distance between two constric-
c
as measured in 6.2,
tions. This value has been found to be relevant to explain the
t = thickness of the geotextile specimen i (mm) as mea-
i
different filtration behaviors of non-woven geotextiles with
sured in 6.2,
similar opening sizes but different structures for various soil
k = class of fibers with a given fiber count and type of
conditions (see Appendix X1 for details).
polymer,
5.3 This value will be used in filtration research to evaluate
p = percentage (in decimal unit, that is, 10 % = 0.1) of
k
the prediction of filtration efficiency and effectiveness of
fibers from a class of fibers k, and
various non-woven geotextiles with similar opening sizes (Test
T = fiber count (tex) associated to a class of fibers k as
k
Method D6767).
measured in 6.3.
5.4 Interpretation of the significance of m as calculated
NOTE 3—Ifthefibercount T isavailableinDenier,dividetheavailable
k
using this standard shall be done with care as some non-woven
value by 9 to obtain the value in Tex.
structures may not reflect the hypothesis used to establish the
proposed equation (see Appendix X1 for details).
7. Report
6. Procedure
7.1 Report the following information:
7.1.1 State that the number of constriction was calculated as
6.1 Condition specimens at 23 6 2°C and 65 % relative
directed in Practice D7178;
humidity for not less than 24 h.
7.1.2 Complete geotextile identification;
6.2 Determine the mass per unit area and thickness of the
geotextile according to Test Methods D5261 and D5199. 7.1.3 Statement of conditioning;
7.1.4 Thickness and mass per unit area of the geotextile:
NOTE 2—Although the thickness of non-woven geotextiles is influ-
individual values and average;
enced by the normal load, the number of constriction shall be calculated
7.1.5 Fiber count distribution / polymer as evaluated in 6.3.
considering the geotextile thickness under 2 kPa for standardization
purpose. Practically, the number of constriction is not influenced by the If it was assumed that only one type of polymer was used to
thickness as it represents the structure of the non-woven (number of
manufacture the geotextile, state this on report;
“windows” delimited by three or more fibe
...
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