1、BRITISH STANDARD BS EN 14576:2005 Geosynthetics Test method for determining the resistance of polymeric geosynthetic barriers to environmental stress cracking The European Standard EN 14576:2005 has the status of a British Standard ICS 59.080.70 BS EN 14576:2005 This British Standard was published u
2、nder the authority of the Standards Policy and Strategy Committee on 27 June 2005 BSI 27 June 2005 ISBN 0 580 46200 5 National foreword This British Standard is the official English language version of EN 14576:2005. The UK participation in its preparation was entrusted to Technical Committee B/553,
3、 Geosynthetics, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catal
4、ogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its cor
5、rect application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests in
6、formed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 14, an inside back cover and a back cover. The BSI copyright notice displayed in this document i
7、ndicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 14576 April 2005 ICS 59.080.70 English version Geosynthetics - Test method for determining the resistance of polymeric geosynthetic barriers to e
8、nvironmental stress cracking Geosynthtiques - Mthode dessai pour la dtermination de la rsistance des gomembranes polymriques la fissuration sous contrainte environnementale Geokunststoffe - Prfverfahren zur Bestimmung der Bestndigkeit von geosynthetischen Kunststoffdichtungsbahnen gegen umweltbeding
9、te 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 an
10、d 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 responsibi
11、lity 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, Germany, Greece, Hungary, Iceland, Ireland, I
12、taly, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Bru
13、ssels 2005 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14576:2005: EEN 14576:2005 (E) 2 Contents Page Foreword3 Introduction .4 1 Scope 5 2 Normative references 5 3 Principle5 4 General requirements and procedure .5 4.1 Apparat
14、us .5 4.1.1 Blanking die5 4.1.2 Notching device .8 4.1.3 Stress cracking apparatus8 4.1.4 Compression moulding press 9 4.1.5 Compression moulding die 9 4.2 Test temperatures9 4.3 Reagent.9 4.4 Test duration 9 4.5 Compression moulding procedure9 4.6 Specimens 10 4.7 Test procedure.10 5 Test report 11
15、 Annex A (informative) Potential supply sources for the equipment 13 Bibliography 14EN 14576:2005 (E) 3 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 s
16、tatus 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, th
17、e 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, Pola
18、nd, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EN 14576:2005 (E) 4 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 ti
19、me 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 surfactant
20、s, 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 unde
21、r 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 A
22、STM 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 pe
23、rformance 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 frequen
24、tly 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 geo
25、synthetic 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 y
26、ield 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 tim
27、e 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 temperatur
28、e, and the time to failure is recorded. The procedure described in this document is based on GRI-GM 5 (b). EN 14576:2005 (E) 5 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
29、 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 us
30、ed 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 th
31、e 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 do
32、cument. 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 spe
33、cimens 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 cutt
34、ing 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 wid
35、ths may be enlarged to accommodate grommets of different sizes with which to attach hooks for the purpose of loading. EN 14576:2005 (E) 6 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 E
36、N 14576:2005 (E) 7 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) EN 14576:2005 (E) 8 4.1.2 Notching device A device or machine that can produce a consistent notch depth shall
37、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
38、 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
39、 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. S i d e v i e w F r o n t v i e w Key 1 Timer micro-switch 2 Lever arm on pivot 3 Specimen supports 4 Specimen 5 Immersion tank on ve
40、rtically 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) EN 14576:2
41、005 (E) 9 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 temp
42、erature of (50 1) C. The equipment should be capable of testing at least 5 specimens at a time. A timing clock for each test specimen shall be provided to record automatically the termination test time of the specimens to the nearest 0,1 h. If on/off switches are used to control the timing clock, th
43、e switch shall be sensitive enough to be turned off under a force of 2 N. 4.1.4 Compression moulding press The press consists of two platens that can be heated to at least 200 C and also are capable to mobilize a force up to 222 kN. 4.1.5 Compression moulding die A single cavity square frame mould w
44、ith area not less than 0,032 m 2and depth of 2,0 mm. The entire steel mould shall have a polished finish without any surface defects. It shall also be strong enough to resist warping or distortion under the stated moulding conditions. NOTE There should be a hole in the upper and lower plates of the
45、mould for placing of a thermocouple in order to monitor the temperature of the plates. 4.2 Test temperatures The test temperature of the test liquid shall be (50 1) C for the whole time of the exposure. 4.3 Reagent The reagent shall consist of 10 % of surface-active agent such as nonylphenoxy polyet
46、hylene-oxyethanol (e.g. Igepal CO-630), diluted with 90 % tap water. The reagent shall be stored in a closed container and the reagent in the bath shall be replaced every two weeks to maintain a constant concentration. NOTE Other incubation solutions may also be used in the test, provided that the p
47、arties involved mutually agree to the changes and state the specific details in the final report. In case of dispute, the dilution water should be either distilled or deionised, at the discretion of the parties involved. 4.4 Test duration The test shall be continued until all five specimens have fai
48、led. However, the test may be discontinued if none of the specimens have failed after an agreed period of time. For evaluation of conformity purposes this period shall be not less than 150 % of the acceptance criterion period stated in the standard pertaining to the application where the geosyntheti
49、c barrier is intended to be used. In such case the test result shall be recorded as “greater than” the time expired when the test is terminated. 4.5 Compression moulding procedure Weigh the amount of resin pellets necessary to fill the volume of the mould based on the density of the resin and a thickness of 2 mm. Place the weighed resin pellets into the mould and place the mould into the press. Once the resin reaches 160 C, a pressure of 3,5 MPa is alternately exerted and re
