Undrained behaviour of granular material and the role of fabric in isotropic and K0 consolidations: DEM approach
Date
2017
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Nguyen, H.B.K.
Rahman, M.M.
Fourie, A.B.
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Géotechnique, 2017; 67(2):153-167
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<jats:p> The behaviour of granular material was investigated by simulating an undrained triaxial compression test for three-dimensional assembly of ellipsoid particles over a wide range of void ratio, e, and mean confining stress, p′. The assembly was either isotropically consolidated or K<jats:sub>0</jats:sub> consolidated prior to undrained shearing up to 30% axial strain to reach steady-state conditions. A unique steady-state line was obtained, irrespective of the consolidation path. The micro-mechanical quantities, such as coordination number and von Mises fabric in terms of second invariant of deviatoric fabric, F<jats:sub>vM</jats:sub>, also reached steady-state values. The normalised anisotropic fabric variable, A, and the trace of the joint stress–fabric tensor, K<jats:sub>F</jats:sub>, evolved during undrained simulation and reached the steady-state value at the end of shearing. This forms a unique relationship in K<jats:sub>F</jats:sub>–p′–e space and the projection of this relationship in e–log(p′) space is the classical steady-state line. This underpins the concept of fabric evolution and steady-state fabric in anisotropic critical state theory. The relationships of state parameter, ψ, and stress ratio at instability, η<jats:sub>IS</jats:sub> = (q/p′)<jats:sub>IS</jats:sub>, were dependent on consolidation path, and the difference was not related to coordination number, but to F<jats:sub>vM</jats:sub>. However, a new phenomenon was observed that stress ratio, η, at the end of K<jats:sub>0</jats:sub> consolidation and η<jats:sub>IS</jats:sub> may reach beyond the steady-state stress ratio, M. Experimental data are needed to verify this; until then such behaviour should be regarded as unproven. </jats:p>
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Copyright 2016 ICE Publishing
Access Condition Notes: Post print available on open access after 1 November 2017