ASTM D4632-91(1996)
(Test Method)Standard Test Method for Grab Breaking Load and Elongation of Geotextiles
Standard Test Method for Grab Breaking Load and Elongation of Geotextiles
SCOPE
1.1 This test method is an index test which provides a procedure for determining the breaking load (grab strength) and elongation (grab elongation) of geotextiles using the grab method. This test method is not suitable for knitted fabrics and alternate test methods should be used. While useful for quality control and acceptance testing for a specific fabric structure, the results can only be used comparatively between fabrics with very similar structures, because each different fabric structure performs in a unique and characteristic manner in this test. The grab test methods does not provide all the information needed for all design applications and other test methods should be used.
1.2 Procedures for measuring the breaking load and elongation by the grab method in both the dry and wet state are included; however, testing is normally done in the dry condition unless specified otherwise in an agreement or specification.
1.3 The values stated in SI units are to be regarded as standard. The values stated in inch-pound units are provided for information only.
1.4 This standard does not purport to address all of the safety problems, 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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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: D 4632 – 91 (Reapproved 1996)
Standard Test Method for
Grab Breaking Load and Elongation of Geotextiles
This standard is issued under the fixed designation D 4632; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 4354 Practice for Sampling of Geosynthetics for Testing
D 4439 Terminology for Geotextiles
1.1 This test method is an index test which provides a
procedure for determining the breaking load (grab strength)
3. Terminology
and elongation (grab elongation) of geotextiles using the grab
3.1 Definitions:
method. This test method is not suitable for knitted fabrics and
3.1.1 atmosphere for testing geotextiles, n— air maintained
alternate test methods should be used. While useful for quality
at a relative humidity of 65 6 5 % relative humidity and
control and acceptance testing for a specific fabric structure,
temperature of 21 6 2°C (70 6 4°F).
the results can only be used comparatively between fabrics
3.1.2 breaking load, n—the maximum force applied to a
with very similar structures, because each different fabric
specimen in a tensile test carried to rupture.
structure performs in a unique and characteristic manner in this
3.1.3 cross-machine direction, n—the direction in the plane
test. The grab test methods does not provide all the information
of the fabric perpendicular to the direction of manufacture.
needed for all design applications and other test methods
3.1.4 elongation at break, n—the elongation corresponding
should be used.
to the breaking load, that is, the maximum load.
1.2 Procedures for measuring the breaking load and elon-
3.1.5 geotextile, n—any permeable textile material used
gation by the grab method in both the dry and wet state are
with foundation, soil, rock, earth, or any other geotechnical
included; however, testing is normally done in the dry condi-
material, as an integral part of a man-made product, structure,
tion unless specified otherwise in an agreement or specifica-
or system.
tion.
3.1.6 grab test, n—in fabric testing, a tension test in which
1.3 The values stated in SI units are to be regarded as
only a part of the width of the specimen is gripped in the
standard. The values stated in inch-pound units are provided
clamps.
for information only.
3.1.6.1 Discussion—For example, if the specimen width is
1.4 This standard does not purport to address all of the
101.6 mm (4 in.) and the width of the jaw faces 25.4 mm (1
safety concerns, if any, associated with its use. It is the
in.), the specimen is gripped centrally in the clamps.
responsibility of the user of this standard to establish appro-
3.1.7 machine direction, n—the direction in the plane of the
priate safety and health practices and determine the applica-
fabric parallel to the direction of manufacture.
bility of regulatory limitations prior to use.
3.1.8 For definitions of other terms used in this test method,
2. Referenced Documents refer to Terminology D 123 or Terminology D 4439.
2.1 ASTM Standards:
4. Summary of Test Method
D 76 Specification for Tensile Testing Machines for Tex-
2 4.1 A continually increasing load is applied longitudinally
tiles
2 to the specimen and the test is carried to rupture. Values for the
D 123 Terminology Relating to Textiles
2 breaking load and elongation of the test specimen are obtained
D 461 Methods of Testing Felt
from machine scales or dials, autographic recording charts, or
D 1682 Test Methods for Breaking Load and Elongation of
2 interfaced computers.
Textile Fabrics
D 1776 Practice for Conditioning Textiles for Testing
5. Significance and Use
D 2905 Practice for Statements on Number of Specimens
2 5.1 The grab method is applicable whenever it is desired to
for Textiles
determine the “effective strength” of the fabric in use, that is,
the strength of the material in a specific width, together with
the additional strength contributed by adjacent material. There
This test method is under the jurisdiction of ASTM Committee D-35 on
Geosynthetics and is the direct responsibility of Subcommittee D35.01 on Mechani-
is no simple relationship between grab tests and strip tests since
cal Properties.
Current edition approved Feb. 22, 1991. Published May 1991. Originally
published as D 4632–86. Last previous edition D 4632–86(1990).
2 3
Annual Book of ASTM Standards, Vol 07.01. Annual Book of ASTM Standards, Vol 04.13.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4632 – 91 (1996)
the amount of fabric assistance depends on the construction of 7.2 Laboratory Sample—Take for the laboratory sample a
the fabric. It is useful as a quality control or acceptance test. swatch extending the width of the fabric and approximately 1
5.2 The procedure in Test Method D 4632 for the determi- m (39.37 in.) along the selvage from each roll in the lot sample.
nation of grab strength of geotextiles may be used for accep- The swatch may be taken from the end portion of a roll
tance testing of commercial shipments, but caution is advised provided there is no evidence that it is distorted or different
since information about between-laboratory precision is in- from other portions of the roll. In cases of dispute, take a
complete. Comparative tests as directed in 5.2.1 are advisable. swatch that will exclude fabric from the outer wrap of the roll
5.2.1 In case of a dispute arising from differences in or the inner wrap around the core.
reported test results when using the procedures in Test Method 7.3 Test Specimens—Cut the number of specimens from
D 4632 for acceptance testing of commercial shipments, the each swatch in the laboratory sample determined as directed in
purchaser and the manufacturer should conduct comparative Section 8. Take no specimens nearer the selvage of fabric edge
tests to determine if there is a statistical bias between their than ⁄20 of the fabric width or 150 mm (6 in.), whichever is the
laboratories. Competent statistical assistance is recommended smaller. Cut rectangular specimens 101.6 by 203.2 mm (4 by 8
for the investigation of bias. As a minimum, the two parties in.). Cut the specimens to be used for grab tests in the machine
should take a group of test specimens that are as homogeneous direction with the longer dimension parallel to the machine
as possible and which are from a lot of material of the type in direction and the specimens to be used for grab tests in the
question. The test specimens should then be randomly assigned cross-machine direction with the longer dimension parallel to
in equal numbers to each laboratory for testing. The average the cross-machine direction. Locate each group of specimens
results from the two laboratories should be compared using the along a diagonal line on the swatch so that each specimen will
appropriate Student’s t-test and an acceptable probability level contain different warp ends and filling picks. Draw a line 37
chosen by the two parties before testing is begun. If a bias is mm (1.5 in.) from the edge of the specimen running its full
found, either its cause must be found and corrected or the length. For woven and reinforced nonwoven fabrics, this line
purchaser and the manufacturer must agree to interpret future must be accurately parallel to the lengthwise yarns in the
test results in the light of the known bias. specimen.
5.3 Most geotextile fabrics can be tested by this test method.
8. Number of Specimens
Some modification of clamping techniques may be necessary
for a given fabric, depending upon its structure. Special 8.1 Unless otherwise agreed upon as when provided in an
adaptation may be necessary with strong fabrics, or fabrics applicable material specification, take a number of test speci-
made from glass fibers, to prevent them from slipping in the mens per swatch in the laboratory sample such that the user
clamps or being damaged as a result of being gripped in the may expect at the 95 % probability level that the test result is
clamps, such as cushioning the clamp or boarding the specimen no more than 5 % above the true average for each swatch in the
within the clamp. laboratory sample for each the machine and cross-machine
5.4 This test method is applicable for testing fabrics either direction, respectively.
dry or wet. It may be used with constant-rate-of-traverse (CRT) 8.1.1 Reliable Estimate of v—When there is a reliable
or constant-rate-of-extension (CRE) type tension machines. estimate of v based upon extensive past records for similar
However, there may be no overall correlation between the materials tested in the user’s laboratory as directed in the
results obtained with the CRT machine and the CRE machine. method, calculate the required number of specimens using Eq
Consequently, these two tension testers cannot be used inter- 1, as follows:
changeably. In case of controversy, the CRE machine shall
n 5 ~tv/A! (1)
prevail.
where:
6. Apparatus
n = number of test specimens (rounded upward to a whole
6.1 Tensile Testing Machine, of the constant-rate-of-
number),
extension (CRE) or constant-rate-of-traverse (CRT) type with v = reliable estimate of the coefficient of variation of
autographic recorder conforming to the requirements of Speci-
individual observations on similar materials in the
fication D 76. user’s laboratory under conditions of single-operator
6.2 Clamps, having all gripping surfaces parallel, flat, and
precision, %,
t = the value of Student’s t for one-sided limits (see Table
capable of preventing slipping of the specimen during a test.
Each clamp shall have one jaw face measuring 25.4 by 50.8 1), a 95 % probability level, and the degrees of
freedom associated with the estimate of v, and
mm (1 by 2 in.), with the longer dimension parallel to the
A = 5.0 % of the average, the value of the allowable
direction of application of the load. The other jaw face of each
variation.
clamp shall be at least as large as its mate. Each jaw face shall
8.1.2 No Reliable Estimate of v—When there is no
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