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Published June 2012 | Published
Journal Article Open

Modelling diffuse instabilities in sands under drained conditions


This paper presents a criterion for detecting diffuse (homogeneous) instabilities in granular soils sheared under fully drained conditions. The criterion is based on bifurcation theory and applied to elasto-plasticity by allowing multiple incremental solutions in elasto-plastic soils, physically losing controllability of stress boundary conditions. Drained diffuse instabilities are poorly understood, and are induced by kinematic modes different from those observed in shear bands and liquefaction instabilities. Unlike shear bands, diffuse instabilities occur under fairly homogenous deformation modes and, unlike liquefaction, drained instabilities are not generated by the excess pore pressures. Recent experiments under drained constant shear report sudden homogeneous instabilities in samples of relatively dense and loose sands. The criterion presented in this paper is used in conjunction with an elasto-plasticity model for sands to predict and explain these reported drained instabilities. From a practical standpoint, these developments serve to expand the repertoire of potential instabilities that occur well before failure, and which have been reported in case studies of puzzling slope instability failures under fully drained conditions.

Additional Information

© 2012 ICE Publishing Ltd. Manuscript received 30 September 2010; revised manuscript accepted 9 September 2011; Published online ahead of print 22 February 2012. AMR acknowledges the partial financial support for the development of this work of Colciencias-Icetex and CEiBA. Support for JEA's work was partially provided by NSF grant number CMMI-1060087, AFOSR grant number FA9550-11- 1-0052 and DOE grant number DE-FG02-08ER15980. This support is gratefully acknowledged.

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Published - Ramos2012p18677Geotechnique.pdf


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