(Received 11 September 2014; accepted 6 July 2015)
Published Online: 2016
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Triaxial tests on soils typically have a latex membrane that confines the test specimen. Because temperature can affect geotechnical test results, laboratory testing is occasionally performed at in situ temperatures, which are typically lower than room temperature. Some long-duration low-temperature triaxial tests have yielded unusual stress path results that do not indicate failure as expected. This study shows that fresh- or salt-water-soaked latex triaxial membranes (as is the condition for a triaxial test) experience a 20-fold increase in stiffness over time at temperatures from just above the freezing point of water to at least 7.5°C. This stiffening comes from partial crystallization of the latex at low temperature. Stiffened membranes do not behave elastically, but exhibit a brittle type of behavior that can adversely affect test results. Variations of latex membrane stiffness with temperature and test duration are presented. These can be used to determine appropriate membrane stiffness corrections for processing triaxial test results. Triaxial tests for which temperature and duration would more than double the latex membrane stiffness are not recommended. Within the range of doubling membrane stiffness at low temperatures, membrane dimensional changes are not significant and may be neglected in the membrane correction.
Norwegian Geotechnical Institute (NGI), Oslo,
Stock #: GTJ20140204