Divergence Instability and Diffuse Failure in Granular Media

A. Daouadji, F. Darve, F. Laouafa, F. Nicot, F. Prunier, L. Sibille, M. Jrad
Procedia IUTAM
Bifurcation, Failure, instability, Kinetic Energy, non associativeness, Second-Order Work

The question of divergence instability and diffuse failure, which is a common failure mode for granular materials like soils, is tackled here from an experimental, theoretical and numerical perspective. The necessary condition of instability as given by the loss of definite-positiveness of the elasto-plastic matrix (the so-called “second order work criterion”) is considered to analyze some experimental tests leading to diffuse failure, the link between kinetic energy and second order work is established, a discrete element method is used to simulate these failure conditions and eventually a 3D bifurcation analysis is performed with incrementally piecewise and non-linear elasto-plastic relationships. Essentially in relation with the non-associate character of the plastic strains of granular materials, a whole bifurcation domain in the stress space emerges from these analyses, leading to novel views of failure for non-associative materials.

Keywords: Instability, Bifurcation, Failure, Kinetic energy, Second order work, Non associativeness

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