Interfacial localisation in simple shear tests on a granular medium modelled as a Cosserat continuum

 
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Interfacial localisation in simple shear tests on a granular medium modelled as a Cosserat continuum (EN)

Unterreiner, P (EN)
Vardoulakis, I (EN)

N/A (EN)

Interfacing of a granular material with a structural member involves the localisation of thedeformations within a few grain diameter thick layer, which is called interface layer. This layer has been shown experimentally to depend mostly on the roughness characteristics and on the grain diameter but not on the geometrical dimensions of the sample or structural member. Among all the interface shear tests available for studying the formation of interfaces in a granular medium, we have selected the plane simple shear test and the ring simple shear test since they allow the sample to deform freely in its volume before interface localisation starts and since they are one dimensional tests (the stress and strain fields depend only on one space variable, the distance to the interface). Within a granular material, individual grains can translate and rotate. A classica continuum takes into account only the transitional degrees of freedom, while a Cosserat continuum considers the additional rotational degrees of freedom. The appropriate equilibrium equations and boundary conditions for such a continuum are derived beforehand by utilising the principle of virtual work. When modelling the plane simple shear test with a clssical continuum, one cannot explain the formation of an interface layer unless ones introduces a strong heterogeneity with a softer material near the interface. The analysis of the ring simple shear test with a classical continuum and rigid plastic constitutive equations yields a boundary layer of plastic material near the interface which has either a zero thickness for an associated material or a thickness directly proportional to the radius of the interface cylinder for a non-associated material. Limitations of a classical continuum can be overcome within the framework of aCosserat continuum. The plane and ring simple shear tests are analysed using linear elastic and rigid plastic contitutive equations respectivley. Both types of constitutive equations introduce an internal material length which is shown to control the thickness of the interface layer independently of the geometric dimensions of the sample. © 1995 Elsevier Ltd. All rights reserved. (EN)

journalArticle

Εθνικό Μετσόβιο Πολυτεχνείο (EL)
National Technical University of Athens (EN)

Studies in Applied Mechanics (EN)

1995


N/A (EN)



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