ASTM D4885-88(1995)
(Test Method)Standard Test Method for Determining Performance Strength of Geomembranes by the Wide Strip Tensile Method
Standard Test Method for Determining Performance Strength of Geomembranes by the Wide Strip Tensile Method
SCOPE
1.1 This test method covers the determination of the performance strength of synthetic geomembranes by subjecting wide strips of material to tensile loading.
1.2 This test method covers the measurement of tensile strength and elongation of geomembranes and includes directions for calculating initial modulus, offset modulus, secant modulus, and breaking toughness.
1.3 The basic distinctions between this test method and other methods measuring tensile strength of geomembranes are the width of the specimens tested and the speed of applied force. The greater width of the specimens specified in this test method minimizes the contraction edge effect (necking) which occurs in many geosynthetics and provides a closer relationship to actual material behavior in service. The slower speed of applied strain also provides a closer relationship to actual material behavior in service.
1.4 As a performance test, this method will be used relatively infrequently, and to test large lots of material. This test method is not intended for routine quality control testing of geomembranes.
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.
1.6 The values stated in SI units are to be regarded as the standard. The inch-pound values stated in parentheses are provided for information only.
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Standards Content (Sample)
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Designation: D 4885 – 88 (Reapproved 1995)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Determining Performance Strength of Geomembranes by
the Wide Strip Tensile Method
This standard is issued under the fixed designation D 4885; 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 882 Test Methods for Tensile Properties of Thin Plastic
Sheeting
1.1 This test method covers the determination of the perfor-
D 1593 Specification for Nonrigid Vinyl Chloride Plastic
mance strength of synthetic geomembranes by subjecting wide
Sheeting
strips of material to tensile loading.
D 1909 Table of Commercial Moisture Regains for Textile
1.2 This test method covers the measurement of tensile
Fibers
strength and elongation of geomembranes and includes direc-
D 4354 Practice for Sampling of Geosynthetics for Testing
tions for calculating initial modulus, offset modulus, secant
D 4439 Terminology for Geosynthetics
modulus, and breaking toughness.
1.3 The basic distinctions between this test method and
3. Terminology
other methods measuring tensile strength of geomembranes are
3.1 Definitions:
the width of the specimens tested and the speed of applied
3.1.1 atmosphere for testing geomembranes, n—air main-
force. The greater width of the specimens specified in this test
tained at a relative humidity of 50 to 70 % and a temperature
method minimizes the contraction edge effect (necking) which
of 21 6 2°C (70 6 4°F).
occurs in many geosynthetics and provides a closer relation-
3.1.1.1 Discussion—Within the range of 50 to 70 % relative
ship to actual material behavior in service. The slower speed of
humidity, moisture content is not expected to affect the tensile
applied strain also provides a closer relationship to actual
properties of geomembrane materials. In addition, geotextile
material behavior in service.
standard test methods restrict the range of relative humidity to
1.4 As a performance test, this method will be used rela-
65 6 5 %, while geomembrane standard test methods restrict
tively infrequently, and to test large lots of material. This test
the range of relative humidity to 55 6 5 %. The restricted
method is not intended for routine quality control testing of
range in this test method is made broader to reduce the need for
geomembranes.
testing laboratories to change laboratory conditions, and con-
1.5 This standard does not purport to address all of the
sidering the lack of expected effect of moisture on geomem-
safety concerns, if any, associated with its use. It is the
branes. The user should consult Table D1909 to resolve
responsibility of the user of this standard to establish appro-
questions regarding moisture regains of textile fibers, espe-
priate safety and health practices and determine the applica-
cially if the user is testing a new or unknown material.
bility of regulatory limitations prior to use.
3.1.2 breaking force, (F), J, n—the force at failure.
1.6 The values stated in SI units are to be regarded as the
−1 −2
3.1.3 breaking toughness, T, (FL ), Jm , n—for geosyn-
standard. The inch-pound values stated in parentheses are
thetics, the actual work per unit volume of a material corre-
provided for information only.
sponding to the breaking force.
2. Referenced Documents 3.1.3.1 Discussion—Breaking toughness is proportional to
the area under the force-elongation curve from the origin to the
2.1 ASTM Standards:
breaking point (see also, work-to-break). Breaking toughness is
D 76 Specification for Tensile Testing Machines for Tex-
2 calculated from work-to-break and width of a specimen. In
tiles
geomembranes, breaking toughness is often expressed as force
D 123 Terminology Relating to Textiles
3 per unit width of material in inch-pound values. In other
D 751 Methods of Testing Coated Fabrics
materials, breaking toughness is often expressed as work per
unit mass of material.
3.1.4 corresponding force, n—synonym for force at speci-
This test method is under the jurisdiction of ASTM Committee D-35 on fied elongation.
Geosynthetics and is the direct responsibility of Subcommittee D35.10 on Geomem-
3.1.5 elastic limit, n— in mechanics, the stress intensity at
branes.
Current edition approved Nov. 25, 1988. Published January 1988.
Annual Book of ASTM Standards, Vols 07.01 and 07.02.
Annual Book of ASTM Standards, Vol 08.01.
Annual Book of ASTM Standards, Vol 09.02.
Annual Book of ASTM Standards, Vol 04.09.
D 4885
which stress and deformation of a material subjected to an 3.1.16 tensile, adj—capable of tensions, or relating to ten-
increasing force cease to be proportional; the limit of stress sion of a material.
−1 −1
within which a material will return to its original size and shape 3.1.17 tensile modulus, J, (FL ), Nm , n—for geosynthet-
when the force is removed, and hence, not a permanent set. ics, the ratio of the change in tensile force per unit width to a
corresponding change in elongation.
3.1.6 failure, n—an arbitrary point beyond which a material
3.1.18 tensile strength, n—the maximum resistance to de-
ceases to be functionally capable of its intended use.
formation developed by a specific material when subjected to
3.1.6.1 Discussion—In wide strip tensile testing of geosyn-
tension by an external force.
thetics, failure occurs either at the rupture point or at the yield
3.1.19 tensile test, n— for geosynthetics, a test in which a
point in the force-elongation curve, whichever occurs first. For
material is stretched uniaxially to determine the force-
reinforced geomembranes, failure occurs at rupture of the
elongation characteristics, the breaking force, or the breaking
reinforcing fabric. For nonreinforced geomembranes which
elongation.
exhibit a yield point, such as polyethylene materials, failure
3.1.20 tension, n—the force that produces a specified elon-
occurs at the yield point. Even though the geomembrane
gation.
continues to elongate, the force-elongation relationship has
3.1.21 wide strip tensile test, n— for geosynthetics, a tensile
been irreversibly altered. For nonreinforced geomembranes
test in which the entire width of a 200 mm (8.0 in.) wide
which do not exhibit a yield point, such as plasticized PVC
specimen is gripped in the clamps and the gage length is 100
materials, failure occurs at rupture of the geomembrane.
mm (4.0 in.).
3.1.7 force at specified elongation, FASE, n—a force asso-
3.1.22 work-to-break, W, (LF), J, n—in tensile testing, the
ciated with a specific elongation on the force-elongation curve.
total energy required to rupture a specimen.
(Synonym for corresponding force.)
3.1.22.1 Discussion—For geomembranes, work-to-break is
3.1.8 force-elongation curve, n— in a tensile test, a graphi-
proportional to the area under the force-elongation curve from
cal representation of the relationship between the magnitude of
the origin to the breaking point.
an externally applied force and the change in length of the
3.1.23 yield point, n— in geosynthetics, the point on the
specimen in the direction of the applied force. (Synonym for
force-elongation curve at which the first derivative equals zero
stress-strain curve.)
(the first maximum).
3.1.9 geomembrane, n—An essentially impermeable geo-
3.1.24 For definitions of other terms used in this test
synthetic used with foundation soil, rock, earth, or any other
method, refer to Terminologies D 123 and D 4439.
geotechnical engineering related material as an integral part of
a man-made project, structure, or system. 4. Summary of Test Method
3.1.9.1 Discussion—Other names under which geomem-
4.1 A relatively wide specimen is gripped across its entire
branes are recognized include: flexible membrane liners
width in the clamps of a constant rate of extension type tensile
(fml’s), liners, and membranes.
testing machine operated at a prescribed rate of extension,
3.1.10 index test, n—a test procedure which may contain a applying a uniaxial load to the specimen until the specimen
known bias, but which may be used to establish an order for a ruptures. Tensile strength, elongation, initial and secant modu-
set of specimens with respect to the property of interest. lus, and breaking toughness of the test specimen can be
calculated from machine scales, dials, recording charts, or an
3.1.11 inflection point, n—the first point of the force-
interfaced computer.
elongation curve at which the second derivative equals zero.
3.1.11.1 Discussion—The inflection point occurs at the first
5. Significance and Use
point on the force-elongation curve at which the curve ceases
5.1 This test method is a performance test intended as a
to curve upward and begins to curve downward (or vice versa).
design aid used to determine the ability of geomembranes to
−1 −1
3.1.12 initial tensile modulus, J , (FL ), Nm , n—for
i
withstand the stresses and strains imposed under design con-
geosynthetics, the ratio of the change in force per unit width to
ditions. This test method assists the design engineer in com-
the change in elongation of the initial portion of a force-
paring several candidate geomembranes under specific test
elongation curve.
conditions.
−1 −1
3.1.13 offset modulus, J , (FL ), Nm , n—for geosyn-
o
5.2 As a performance test, this method is not intended for
thetics, the ratio of the change in force per unit width to the
routine acceptance testing of commercial shipments of
change in elongation below an arbitrary offset point at which
geomembranes. Other more easily performed test methods,
there is a proportional relationship between force and elonga-
such as Method D 751 or Test Method D 882, can be used for
tion, and above the inflection point on the force-elongation
routine acceptance testing of geomembranes. This test method
curve.
will be used relatively infrequently, and to establish perfor-
3.1.14 performance test, n—a test
mance characteristics of geomembrane materials.
which simulates in the laboratory as closely as practicable
5.2.1 There is no known correlation between this test
selected conditions experienced in the field and which can be
method and index test methods, such as Method D 751.
used in design. (Synonym for design test.)
5.3 All geomembranes can be tested by this method. Some
−1 −1
3.1.15 secant modulus, J , (FL ), Nm , n—for geosyn- modification of techniques may be necessary for a given
sec
thetics, the ratio of change in force per unit width to the change geomembrane depending upon its physical make-up. Special
in elongation between two points on a force-elongation curve. adaptations may be necessary with strong geomembranes or
D 4885
geomembranes with extremely slick surfaces, to prevent them sphere. Consider the specimen to be at moisture equilibrium
from slipping in the clamps or being damaged by the clamps. when the change in mass of the specimen in successive
weighings made at intervals of not less than 2 h does not
6. Apparatus
exceed 0.1 % of the mass of the specimen. Consider the
specimen to be at temperature equilibrium after1hof exposure
6.1 Clamps—A gripping system that minimizes (with the
goal of eliminating) slippage, damage to the specimen, and to the standard atmosphere for testing.
uneven stress distribution. The gripping system shall extend to
9. Procedure
or beyond the outer edge of the specimen to be tested.
6.2 Specimen Cutter—An appropriate cutting device which
9.1 Test adequately conditioned specimens. Conduct tests at
does not create irregularities or imperfections in the edge of the
a temperature of 21 6 2°C (70 6 4°F) and at a relative
specimen. For wide strip specimens, a jig may not be necessary
humidity of 50 to 70 %. The engineer may specify additional
provided that the actual cut dimensions of the specimen can be
temperatures based upon expected service conditions for the
measured accurately to the nearest 1.0 mm (0.04 in.), and that
installation.
the width of the specimen is constant to within 1.0 mm (0.04
9.2 Measure for the specimens thickness at the four corners
in.).
of the specimen. Select specimens used in this procedure so
6.3 Tensile Testing Machine—A testing machine of the
that thickness is uniform to within 5 %. Measure thickness
constant rate of extension type as described in Specification
using either Specification D 1593 for nonreinforced geomem-
D 76 shall be used. The machine shall be equipped with a
branes or Method D 751 for reinforced geomembranes.
device for recording the tensile force and the amount of
9.3 Position the grips of the testing apparatus to a separation
separation of the grips. Both of these measuring systems shall
of 100 6 3mm(4 6 0.1 in.). At least one clamp should be
be accurate to 62 % and, preferably, shall be external to the
supported by a free swivel or universal joint which will allow
testing machine. The rate of separation shall be uniform and
the clamp to rotate in the plane of the fabric. Select the force
capable of adjustment within the range of the test.
range of the testing machine so that the break occurs between
10 and 90 % of full scale load. Set the machine to a strain rate
7. Sampling
as directed in 9.6.
7.1 Lot Sample—Divide the product into lots and take the
9.4 Mount the specimen centrally in the clamps. Do this by
lot sample as directed in Practice D 4354.
having the two lines, which were previously drawn 100 6 3
7.2 Laboratory Sample—For the laboratory sample, take a
mm (4.06 0.1 in.) apart across the width of the specimen as
full-width swatch approximately 1 m (40 in.) long in the
close as possible adjacent to the inside edges of the upper and
machine direction from each roll in the lot sample. The sample
lower jaw. The specimen length in the machine direction and
may be taken from the end portion of a roll provided there is
the cross machine direction tests, respectively, must be parallel
no evidence it is distorted or different from other portions of
to the direction of application of force.
the roll.
9.5 Start the tensile testing machine and the area measuring
7.3 Test Specimens—Take a total of twelve specimens from
device, if used, and continue running the test to rupture. Stop
each swatch in the laboratory sample, with six specimens for
the machine and reset to the initial gage position. Record and
tests in the machine direction and six specimens for tests in the
report the test results to three significant figures for each
cross-machine direction. Take the specimens from
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