EN 14576:2005

SLOVENSKI STANDARD
01-julij-2005
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Geosynthetics - Test method for determining the resistance of polymeric geosynthetic
barriers to environmental stress cracking
Geokunststoffe - Prüfverfahren zur Bestimmung der Beständigkeit von geosynthetischen
Kunststoffdichtungsbahnen gegen umweltbedingte Spannungsrissbildung
Géosynthétiques - Méthode d'essai pour la détermination de la résistance des barrieres
géosynthétiques polymériques a la fissuration sous contrainte environnementale
Ta slovenski standard je istoveten z: EN 14576:2005
ICS:
59.080.70 Geotekstilije Geotextiles
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 14576
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2005
ICS 59.080.70
English version
Geosynthetics - Test method for determining the resistance of
polymeric geosynthetic barriers to environmental stress cracking
Geosynthétiques - Méthode d'essai pour la détermination Geokunststoffe - Prüfverfahren zur Bestimmung der
de la résistance des géomembranes polymériques à la Beständigkeit von geosynthetischen
fissuration sous contrainte environnementale Kunststoffdichtungsbahnen gegen umweltbedingte
Spannungsrissbildung
This European Standard was approved by CEN on 3 March 2005.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
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Slovenia, Spain, Sweden, Switzerland and United Kingdom.
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© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 14576:2005: E
worldwide for CEN national Members.

Contents Page
Foreword.3
Introduction .4
1 Scope .5
2 Normative references .5
3 Principle.5
4 General requirements and procedure .5
4.1 Apparatus .5
4.1.1 Blanking die.5
4.1.2 Notching device .8
4.1.3 Stress cracking apparatus.8
4.1.4 Compression moulding press .9
4.1.5 Compression moulding die .9
4.2 Test temperatures.9
4.3 Reagent.9
4.4 Test duration .9
4.5 Compression moulding procedure.9
4.6 Specimens .10
4.7 Test procedure.10
5 Test report .11
Annex A (informative) Potential supply sources for the equipment .13
Bibliography .14

Foreword
This document (EN 14576:2005) has been prepared by Technical Committee CEN/TC 189 “Geosynthetics”,
the secretariat of which is held by IBN/BIN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by October 2005, and conflicting national standards shall be withdrawn at
the latest by October 2005.
This document includes a Bibliography.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland
and United Kingdom.
Introduction
Stress cracking is a phenomenon observed in most thermoplastic materials. It is defined as internal or
external cracking of the material caused by tensile stresses less than the short time mechanical strength of
the material. Stress cracking may limit the durability of e.g. thermoplastic pipes and geosynthetic barriers. In
addition to the influence of the stress, stress cracking is accelerated by elevated temperature and the
presence of certain molecular species, such as surfactants, in the surrounding environment.
The ability of a material to withstand stress cracking is known as its stress crack resistance. Stress crack
resistance is measured by the time required to failure when a specimen of the material is immersed in a
particular medium at elevated temperature while under a defined stress. Stress crack resistance is primarily a
function of the resin (thermoplastic raw material) type but may be adversly influenced by the geosynthetic
barrier manufacturing process particularly certain procedures for friction enhancement. The so-called "bent
strip” test described in ASTM D 1693, was used as a screening test for many years. However this method has
been found to provide misleading results due to relaxation of the specimen and reduction of the stress level
during increased testing periods. In consequence the “bent strip” test has been unable to differentiate the
performance of improved resins requiring longer testing periods.
To meet the requirement to accurately quantify and differentiate the performance of modern resins the
Geosynthetics Institute (formerly Geosynthetics Research Institute) developed an alternative method GRI-
GM5. The GRI method is frequently referred to as the notched constant tensile load" (NCTL) test as the
apparatus used ensures a constant level of stress in the specimen throughout the test and the specimen is
notched to provide a concentration point for stress and failure. The NCTL test is now used extensively
throughout the geosynthetic barrier industry.
The NCTL test can be performed under two separate procedures that are described in GRI-GM 5 (a) and 5 (b).
In the procedure GRI-GM 5 (a), the so-called full curve test”, specimens are immersed in the test liquid at a
range of stresses, typically from 20 % to 65 % of the yield strength of the material. The time to failure and the
failure mode (brittle or ductile) is recorded at each level of stress. Failure time is plotted against stress.
Typically the resulting curve will show an abrupt change in slope at a point that coincides with a change in
failure mode. The time at which this occurs is recorded as the transition time”.
The second variant of the test, GRI-GM 5 (b), which is simpler and quicker to perform, is known as the "single
point" test. In this case the specimens are tested at 30 % of the measured yield stress of the material at
normal room temperature, and the time to failure is recorded. The procedure described in this document is
based on GRI-GM 5 (b).
1 Scope
This document specifies a test method for screening the resistance of polymeric geosynthetic barriers to
stress cracking. The test is applicable to polypropylene and polyethylene based products and to all other
polymeric geosynthetic barriers which have a partially crystalline structure.
NOTE The described method is suitable for conformance testing of smooth surfaced (non-textured) geosynthetic
barriers. However the resistance to stress cracking of the resin used in the manufacture of structured surface materials
can be evaluated by carrying out the test on a plaque formed from the relevant resin (see 4.5) or, where structuring is
carried out as a separate processing step, on a preformed smooth surface geosynthetic barrier, the test can be performed
on the intermediate smooth material.
The data are suitable for screening and determination of conformity but not for deriving performance data
such as lifetime, unless supported by further evidence.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN ISO 9862, Geosynthetics - Sampling and preparation of test specimens (ISO 9862:2005)
3 Principle
Dumbbell shaped notched test specimens cut from the geosynthetic barrier are subjected to a constant tensile
load in the presence of a surface active agent at an elevated temperature. The time to failure of each test
specimen is recorded.
4 General requirements and procedure
4.1 Apparatus
4.1.1 Blanking die
A die suitable for cutting test specimens to the dimensions and tolerances is shown in Figure 1a.
NOTE The length of the specimen can be changed to suit the design of the test apparatus. However, there should be
a constant width neck section at least 13 mm long. The width of the neck section should be 3,17 mm. The tab widths may
be enlarged to accommodate grommets of different sizes with which to attach hooks for the purpose of loading.
Dimensions in millimetres
NOTE Dimensions may be varied to suit equipment with the exception of the neck dimensions shown*
Figure 1a – Dimensions of test specimen
Key
t Thickness
1 Notch (0,2 × t)
Figure 1b – Isometric view of cut specimen (not to scale)

Key
t Thickness
1 Notch (0,2 × t)
Figure 1c – Side view of cut specimen (not to scale)

4.1.2 Notching device
A device or machine that can produce a consistent notch depth shall be used.
NOTE The notch should consist of a single cut with a thin blade. There should be no removal of the specimen
material. An evaluation of the depth produced by the notching technique can be performed by quenching a notched
specimen in liquid nitrogen and then fracturing it. The notch depth can readily be measured by examining the fracture
surface under a reflected light microscope.
4.1.3 Stress cracking apparatus
A typical stress cracking apparatus is schematically represented in Figure 2.
The equipment shall be suitable for subjecting multiple test specimens to a tensile stress of up to 13,8 MPa,
using a lever arm and adjustable counterweight system, while they are totally immersed in a surface-active
agent contained in an open stainless steel tank.

Side view     Front view
Key
1 Timer micro-switch
2 Lever arm on pivot
3 Specimen supports
4 Specimen
5 Immersion tank on vertically adjustable support
6 Adjustable load
NOTE The counterweight should be located outside the tank and should be continuously adjustable within the required
range. A shot can or similar device would be suitable.
Figure 2 – Typical stress cracking apparatus (with approximate dimensions)
Suitable hooks or clamps are required to secure the specimen to the base of the tank and to the lever arm.
The equipment shall be capable of constantly agitating the solution by pumping or other means, to provide a
uniform concentration throughout the bath while maintaining a constant temperature of (50 ± 1) °C. The
equipment should be cap
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