Triggering Mechanisms Of Soil Instability
Author(s)
A. Daouadji, H.Al Gali & F.Darve
Abstract
In this study, we present a device designed to investigate the behavior of very loose
sand subjected to strain and stress loading paths. The influence of these loading
paths is analyzed with particular attention to potential instabilities. Comparisons
are made with results obtained from experimental data from literature. A particular
stress path, i.e. a constant shear undrained path, is then detailed and results are
discussed. Experimental results show that diffuse mode failure occurs before the
Mohr-Coulomb failure surface is reached. It is shown for these undrained tests that
excess pore pressure results from collapse and it is not a trigger parameter.
Keywords: instability, collapse, very loose sand, constant shear undrained path,
diffuse failure, load-controlled triaxial tests.
1 Introduction
Several studies have shown that a plastic limit criterion, such the Mohr-Coulomb
criterion, does not explain all the types of ruptures that occur in soils. Previous
studies well explain the localization phenomena that can occur during the load-ing.
Failure is often the result of strain localization (vanishing determinant of the
acoustic tensor as criterion, for example) which is close to, but does not reach,
the Mohr-Coulomb criterion. However, in case of very loose sands, recent studies
(Servant et al. [15]) have shown that failure can develop in a diffuse mode and in
this case the observed failure mode is a diffuse collapse. Diffuse mode implies that
criterion for bifurcation are reached before the localization criterion. It is important
to note that these collapses strictly occur inside Mohr-Coulomb plastic limit crite-rion
and that the conventional failure analysis cannot explain them. Indeed, some
Keywords
instability, collapse, very loose sand, constant shear undrained path,
diffuse failure, load-controlled triaxial tests.
Related Book
Other papers in this volume
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