The University of Massachusetts Amherst
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Non-uniqueness of critical state line in compression and extension conditions

TitleNon-uniqueness of critical state line in compression and extension conditions
Publication TypeJournal Article
Year of Publication2009
AuthorsYin Z-Y, Chang CS
JournalInternational Journal for Numerical and Analytical Methods in Geomechanics
Start Page1315
Date Published01/2009
KeywordsClays, Constitutive relations, critical state, extension test, Micromechanics, plasticity

Experimental evidence has indicated that the critical state line determined from undrained compression tests is not identical to that determined from undrained extension tests. The purpose of this paper is to investigate a modelling method that accounts for the non-uniqueness of critical state lines in the compression and the extension testing conditions. Conventional elastic–plastic cap models can predict only a unique critical state line for the compression and the extension tests. A new micromechanical stress– strain model is developed considering explicitly the location of critical state line. The model is then used to simulate undrained triaxial compression and extension tests performed on isotropically consolidated samples with different over-consolidated ratios. The predictions are compared with experimental results as well as that predicted by models with kinematic hardening of yield surface. All simulations demonstrate that the proposed micromechanical approach is capable of modelling the undrained compression and the undrained extension tests