ASTM D7748-12e1
(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 standard. 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 SI units are to be regarded as the standard. The U.S. customary units may be approximate.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D7748 − 12
StandardTest Method for
Flexural Rigidity of Geogrids, Geotextiles and Related
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Products
This standard is issued under the fixed designation D7748; 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.
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´ NOTE—This test method was editorially corrected in May 2012.
1. Scope 3. Terminology
1.1 This test method covers the measurement of stiffness
3.1 For common definitions of terms in this test method,
properties of geogrids, geotextiles and geogrid-geotextile com-
refer to Terminology D123 and Terminology D4439
posites all of which are referred to as geosynthetics within this
3.2 Definitions of Terms Specific to This Standard:
standard. Bending length is measured and flexural rigidity is
3.2.1 bending length, n—a measure of the interaction be-
calculated through use of the cantilever test procedure.
tween geosynthetic weight and geosynthetic stiffness as shown
1.1.1 This test method employs the principle of cantilever
by the way in which a geosynthetic bends under its own
bending of the geosynthetic under its own mass.
weight.
1.2 This test method applies to geogrids, geotextiles and
3.2.1.1 Discussion—Bending length reflects the stiffness of
geogrid-geotextile composites.
a geosynthetic when bent in one plane under the force of
1.3 This test method is for manufacturing quality control gravity.
purposes only, to ensure uniformity and consistency of flexural
rigidity for a specific product from roll to roll and lot to lot. 4. Summary of Test Method
1.4 The values stated in SI units are to be regarded as the
4.1 A specimen is slid at a specified rate in a direction
standard. The U.S. customary units may be approximate.
parallel to its long dimension, until its leading edge projects
from the edge of a horizontal surface. The length of the
1.5 This standard does not purport to address all of the
overhang is measured when the tip of the specimen is de-
safety concerns, if any, associated with its use. It is the
pressed under its own mass to the point where the line joining
responsibility of the user of this standard to establish appro-
the top to the edge of the platform makes a 0.724 radians
priate safety and health practices and determine the applica-
(41.5°) angle with the horizontal. From this measured length,
bility of regulatory limitations prior to use.
the bending length and flexural rigidity are calculated.
2. Referenced Documents
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5. Significance and Use
2.1 ASTM Standards:
D123 Terminology Relating to Textiles
5.1 This test method is considered satisfactory for manufac-
D1776 Practice for Conditioning and Testing Textiles
turing quality control testing of a specific geosynthetic;
D4354 Practice for Sampling of Geosynthetics for Testing
however, caution is advised since information about between-
D4439 Terminology for Geosynthetics
laboratory precision is incomplete. Comparative tests as di-
D4759 Practice for Determining the Specification Confor-
rected in 5.1.1 may be advisable.
mance of Geosynthetics
5.1.1 In case of a dispute arising from differences in
D5261 Test Method for Measuring Mass per Unit Area of
reported test results when using this test method for acceptance
Geotextiles
testing of commercial shipments, the purchaser and the sup-
plier should conduct comparative tests to determine if there is
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This test method is under the jurisdiction of ASTM Committee D35 on
a statistical bias between their laboratories. Competent statis-
Geosynthetics and is the direct responsibility of Subcommittee D35.01 on Mechani-
tical assistance is recommended for the investigation of bias.
cal Properties.
As a minimum, the two parties should take a group of test
Current edition approved Feb. 1, 2012. Published March 2012. DOI: 10.1520/
D7748–12E01
specimens that are as homogeneous as possible and that are
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
from a lot of material of the type in question. Test specimens
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
should then be randomly assigned in equal numbers to each
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. laboratory for testing. The average results from the two
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D7748 − 12
laboratories should be compared using the appropriate statis- 7. Sampling and Test Specimens
tical analysis and an acceptable probability level chosen by the
7.1 Lot Sample—As a lot samp
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