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Multi-Axial Tension Behavior of Smooth HDPE Geomembrane at Extremely Slow Pressurization Rates
Since 1990, the multi-axial tension test has been regularly used to assess the ability of geomembranes to undergo out-of-plane deformations as in cases of rising gas bubbles or differential settlements. The test method is also referred to as a axi-symmetric or three-dimensional tension test. The laboratory test procedure followed is either GRI-GM4 or ASTM D5617, which are similar but conducted at pressurization rates of 6.9 kPa/min and 20 mm/min, respectively. While such rates appear reasonable for index properties of most geomembrane types, semi-crystalline geomembranes like high density polyethylene (HDPE) might be better represented at slower, or even extremely slower, pressurization rates. This experimental study was undertaken to investigate this possibility. Using eight sequentially slower pressurization rates from the default value down to 0.000157 kPa/min (44,000 times slower) the strength values were not markedly changed (yield was unchanged and break increased slightly). However, the limiting strain values changed considerably (yield increased by 200% and break increased by 400%). Thus it is felt that the field performance of HDPE geomembranes can best be simulated by conducting the multi-axial test at very slow pressurization rates. While such rates are not practical in the context of an index test method the authors feel that some type of commentary to this effect could well be included in the respective test method standards.
Multi-Axial Tension Behavior of Smooth HDPE Geomembrane at Extremely Slow Pressurization Rates
Since 1990, the multi-axial tension test has been regularly used to assess the ability of geomembranes to undergo out-of-plane deformations as in cases of rising gas bubbles or differential settlements. The test method is also referred to as a axi-symmetric or three-dimensional tension test. The laboratory test procedure followed is either GRI-GM4 or ASTM D5617, which are similar but conducted at pressurization rates of 6.9 kPa/min and 20 mm/min, respectively. While such rates appear reasonable for index properties of most geomembrane types, semi-crystalline geomembranes like high density polyethylene (HDPE) might be better represented at slower, or even extremely slower, pressurization rates. This experimental study was undertaken to investigate this possibility. Using eight sequentially slower pressurization rates from the default value down to 0.000157 kPa/min (44,000 times slower) the strength values were not markedly changed (yield was unchanged and break increased slightly). However, the limiting strain values changed considerably (yield increased by 200% and break increased by 400%). Thus it is felt that the field performance of HDPE geomembranes can best be simulated by conducting the multi-axial test at very slow pressurization rates. While such rates are not practical in the context of an index test method the authors feel that some type of commentary to this effect could well be included in the respective test method standards.
Multi-Axial Tension Behavior of Smooth HDPE Geomembrane at Extremely Slow Pressurization Rates
Koerner, Robert M. (Autor:in) / Koerner, George R. (Autor:in) / Hsuan, Y. Grace (Autor:in)
Geosynthetics, Geosynthetics Conference, 2015 ; 1200-1209
2015
10 Seiten, Bilder, Tabellen, Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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