ASTM D7748/D7748M-14(2021)
(Test Method)Standard Test Method for Flexural Rigidity of Geogrids, Geotextiles, and Related Products
Standard Test Method for Flexural Rigidity of Geogrids, Geotextiles, and Related Products
SIGNIFICANCE AND USE
5.1 This test method is considered satisfactory for manufacturing quality control testing of a specific geosynthetic; however, caution is advised since information about between-laboratory precision is incomplete. Comparative tests as directed in 5.1.1 may be advisable.
5.1.1 In case of a dispute arising from differences in reported test results when using this test method for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type in question. Test specimens should then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using the appropriate statistical analysis and an acceptable probability level chosen by the two parties before testing is begun. If a bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results with consideration to the known bias.
5.2 This test method is not suitable for very limp geosynthetics or those that show a marked tendency to curl or twist at a cut edge.
5.3 The stiffness of a geosynthetic may change with storage.
5.4 No evidence has been found showing that bending length is dependent on specimen width. The tendency for specimens to curl or twist will affect the result, because of the rigidity provided at the edge. Consequently, the edge effect is less of an issue for a wider strip.
SCOPE
1.1 This test method covers the measurement of stiffness properties of geogrids, geotextiles, and geogrid-geotextile composites, all of which are referred to as geosynthetics within this test method. Bending length is measured and flexural rigidity is calculated through use of the cantilever test procedure.
1.1.1 This test method employs the principle of cantilever bending of the geosynthetic under its own mass.
1.2 This test method applies to geogrids, geotextiles, and geogrid-geotextile composites.
1.3 This test method is for manufacturing quality control purposes only, to ensure uniformity and consistency of flexural rigidity for a specific product from roll to roll and lot to lot.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.
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
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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: D7748/D7748M − 14 (Reapproved 2021)
Standard Test Method for
Flexural Rigidity of Geogrids, Geotextiles, and Related
Products
This standard is issued under the fixed designation D7748/D7748M; 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
2.1 ASTM Standards:
1.1 This test method covers the measurement of stiffness
D123 Terminology Relating to Textiles
properties of geogrids, geotextiles, and geogrid-geotextile
D1776/D1776M Practice for Conditioning and Testing Tex-
composites, all of which are referred to as geosynthetics within
tiles
this test method. Bending length is measured and flexural
D4354 Practice for Sampling of Geosynthetics and Rolled
rigidity is calculated through use of the cantilever test proce-
Erosion Control Products (RECPs) for Testing
dure.
D4439 Terminology for Geosynthetics
1.1.1 This test method employs the principle of cantilever
E177 Practice for Use of the Terms Precision and Bias in
bending of the geosynthetic under its own mass.
ASTM Test Methods
1.2 This test method applies to geogrids, geotextiles, and
E691 Practice for Conducting an Interlaboratory Study to
geogrid-geotextile composites. Determine the Precision of a Test Method
1.3 This test method is for manufacturing quality control
3. Terminology
purposes only, to ensure uniformity and consistency of flexural
rigidity for a specific product from roll to roll and lot to lot. 3.1 For common definitions of terms in this test method,
refer to Terminology D123 and Terminology D4439.
1.4 The values stated in either SI units or inch-pound units
3.2 Definitions of Terms Specific to This Standard:
are to be regarded separately as standard. The values stated in
3.2.1 bending length, n—a measure of the interaction be-
each system are not necessarily exact equivalents; therefore, to
tween geosynthetic weight and geosynthetic stiffness as shown
ensure conformance with the standard, each system shall be
by the way in which a geosynthetic bends under its own
used independently of the other, and values from the two
weight.
systems shall not be combined.
3.2.1.1 Discussion—Bending length reflects the stiffness of
1.5 This standard does not purport to address all of the
a geosynthetic when bent in one plane under the force of
safety concerns, if any, associated with its use. It is the
gravity.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
4.1 A specimen is slid at a specified rate in a direction
1.6 This international standard was developed in accor-
parallel to its long dimension, until its leading edge projects
dance with internationally recognized principles on standard-
from the edge of a horizontal surface. The length of the
ization established in the Decision on Principles for the
overhang is measured when the tip of the specimen is de-
Development of International Standards, Guides and Recom-
pressed under its own mass to the point where the line joining
mendations issued by the World Trade Organization Technical
the top to the edge of the platform makes a 0.724 radians
Barriers to Trade (TBT) Committee.
[41.5°] angle with the horizontal. From this measured length,
the bending length and flexural rigidity are calculated.
This test method is under the jurisdiction of ASTM Committee D35 on
Geosynthetics and is the direct responsibility of Subcommittee D35.01 on Mechani-
cal Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Sept. 1, 2021. Published September 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2012. Last previous edition approved in 2014 as D7748/D7748M – 14. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D7748_D7748M-14R21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7748/D7748M − 14 (2021)
5. Significance and Use 6.1.1 Horizontal Platform, with a minimum area of 100 by
900 mm [4 by 36 in.] and having a smooth low-friction, flat
5.1 This test method is considered satisfactory for manufac-
aluminum surface. A leveling bubble shall be incorporated in
turing quality control testing of a specific geosynthetic;
the platform.
however, caution is advised since information about between-
6.1.1.1 Indicator, inclined at an angle of 0.724 6 0.01
laboratory precision is incomplete. Comparative tests as di-
radians [41.5 6 0.5°] below the plane of the platform surface.
rected in 5.1.1 may be advisable.
6.1.1.2 Movable Slide, consisting of a metal plate not less
5.1.1 In case of a dispute arising from differences in
than 50 by 200 mm [2 by 8 in.] by approximately 3 mm [ ⁄8 in.]
reported test results when using this test method for acceptance
thick and having a mass of 270 6 5 g [0.6 6 0.01 lb].
testing of commercial shipments, the purchaser and the sup-
plier should conduct comparative tests to determine if there is 6.1.1.3 Scale and Reference Point, to measure the length of
a statistical bias between their laboratories. Competent statis- the overhang.
tical assistance is recommended for the investigation of bias.
6.1.1.4 Specimen Feed Unit, motorized set to 120 mm/min
As a minimum, the two parties should take a group of test
[4.75 in./min] 6 5 %, or manual equivalent.
specimens that are as homogeneous as possible and that are
from a lot of material of the type in question. Test specimens
7. Sampling and Test Specimens
should then be randomly assigned in equal numbers to each
7.1 Lot Sample—As a lot sample for acceptance testing,
laboratory for testing. The average results from the two
randomly select the number of rolls or pieces of geosynthetic
laboratories should be compared using the appropriate statis-
directed in an applicable material specification or other agree-
tical analysis and an acceptable probability level chosen by the
mentbetweenthepurchaserandthesupplier.Considertherolls
two parties before testing is begun. If a bias is found, either its
or pieces of geosynthetic to be the primary sampling units. In
cause must be found and corrected or the purchaser and the
the absence of such an agreement, take the number of geosyn-
supplier must agree to interpret future test results with consid-
thetic rolls specified in Practice D4354.
eration to the known bias.
7.2 For acceptance testing, take a swatch extending the
5.2 This test method is not suitable for very limp geosyn-
width of the geosynthetic and approximately2m[6ft] along
thetics or those that show a marked tendency to curl or twist at
the machine direction from each roll or piece in the lot sample.
a cut edge.
For rolls of geosynthetic, take a sample that will exclude
5.3 The stiffness of a geosynthetic may change with storage.
geosynthetic from the outer wrap of the roll or the inner wrap
5.4 No evidence has been found showing that bending
around the core of the roll of geosynthetic, or any end piece.
length is dependent on specimen width. The tendency for
7.3 Direction of Test—Consider the long dimension of the
specimens to curl or twist will affect the result, because of the
specimen as the direction of test.
rigidity provided at the edge. Consequently, the edge effect is
less of an issue for a wider strip. 7.4 Number of Test Specimens—From each laboratory sam-
pling unit, take five specimens from the machine direction and
6. Apparatus
five specimens from the cross-machine direction as applicable
6.1 Flexural Rigidity Tester (Fig. 1). to a material specification or contract order.
FIG. 1 Example Test Rig Setup
D7748/D7748M − 14 (2021)
7.5 Cutting Test Specimens—Cut the specimens to be used 10.2 Remove the movable slide. Place the specimen on the
for the measurement of machine direction with the longer horizontal platform with the length of the specimen parallel to
dimension parallel to the machine direction. Cut the specimens the platform edge and the specimen face side up. Align the
to be used for the measurement of the cross-machine direction edge of the specimen with the line scribed on the right-hand
with the longer dimension parallel to the cross-machine direc- edge of the horizontal platform.
tion. Label to maintain specimen identity. 10.2.1 Place the movable slide on the specimen, being
7.5.1 Take specimens representing a broad distribution careful not to change its initial position.
across the width and length, preferably along the diagonal of 10.2.2 For automatic testers, turn the tester switch on and
the laboratory sample, and no nearer the edge than one tenth its watch the leading edge of the specimen closely. Turn the
width. Ensure specimens are free of folds, creases, or wrinkles. switch off the instant the edge of the specimen touches the
Avoid getting oil, water, grease, etc. on the specimens when inclined portion of the tester.
handling. 10.2.3 For manual testers, move the clamped specimen by
7.5.2 For geogrids and geotextile-geogrid composites, cut handinasmoothmanneratapproximately12cm/min[4.75 in-
specimen such that the specimen includes two (2) geogrid .⁄min] 6 5 % until the edge of the specimen touches the
apertures in width or a minimum of 5 by 90 cm 6 0.1 cm inclined portion of the tester, as shown in Figs. 2 and 3.
[minimum of 2 by 36 in. 6 0.04 in.]. 10.2.4 Read the overhang length by measuring the length
7.5.2.1 It is important to cut the ribs of the specimens in still lying on the horizontal surface after the specimen has
both the width and the length direction exactly midway touched the inclined surface and subtracting that measurement
between junctions such that a representative mass per unit area from the initial specimen length. Record from the linear scale
can be obtained for each specimen. to the nearest 0.1 cm [0.1 in.].
7.5.3 For geotextiles, cut test specimens 5 by 90 cm 6
NOTE 1—If the specimen has a tendency to twist, take the reference
0.1 cm [2 by 36 in. 6 0.04 in.].
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