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Micromechanical insight into the undrained instability of granular materials: deformation characteristics of geomaterials.

Barreto, Daniel; Prada-Sarmiento, Luis Felipe; Ramos-Ca��n, Alfonso Mariano


Luis Felipe Prada-Sarmiento

Alfonso Mariano Ramos-Ca��n


Victor A Rinaldi

Marcello E Zeballos

Juan Jose Clari�


There is no agreement between experimental researchers whether the point where a granular material responds with a large change of stresses, strains or excess pore water pressure given a prescribed small input of some of the same variables defines a straight line or a curve in the stress space. This line, known as the instability line, may also vary in shape and position if the onset of instability is measured from drained or undrained triaxial tests.

Failure of granular materials, which might be preceded by the onset of instability, is a subject that the geotechnical engineers have to deal with in the daily practice, and generally speaking it is associated to different phenomena observed not only in laboratory tests but also in the field. Examples of this are the liquefaction of loose sands subjected to undrained loading conditions and the diffuse instability under drained loading conditions.

This research presents results of DEM simulations of undrained triaxial tests with the aim of studying the influence of stress history and relative density on the onset of instability in granular materials. Micro-mechanical analysis including the evolution of coordination numbers and fabric tensors is performed aiming to gain further insight on the particle-scale interactions that underlie the occurrence of this instability. In addition to provide a greater understanding, the results presented here may be useful as input for macro-scale constitutive models that enable the prediction of the onset of instability in boundary value problems.


Barreto, D., Prada-Sarmiento, L. F., & Ramos-Cañón, A. M. (2015). Micromechanical insight into the undrained instability of granular materials: deformation characteristics of geomaterials. In V. A. Rinaldi, M. E. Zeballos, & J. J. Clariá (Eds.), Deformation Characteristics of Geomaterials (655-662).

Conference Name 6th International Symposium on Deformation Characteristics of Geomaterials
Start Date Nov 15, 2015
End Date Nov 18, 2015
Acceptance Date Sep 9, 1999
Publication Date Dec 11, 2015
Deposit Date Jun 8, 2016
Publisher IOS Press
Peer Reviewed Not Peer Reviewed
Volume 6
Pages 655-662
Series Title Advances in Soil Mechanics and Geotechnical Engineering Vol. 6
Series ISSN 2212-781X
Book Title Deformation Characteristics of Geomaterials
ISBN 9781614996019, 978-1-61499-601-9,
Keywords Granular material; instability line; water pressure; triaxial tests;
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