The use of strain energy as a yield and creep criterion for lightly overconsolidated clays

Abstract

Triaxial, stress controlled, drained tests on four undisturbed, overconsolidated clays from eastern Canada show that the strain energy can be used with advantage to define the limit state surface of such clays since a clear discontinuity in the energy–stress relationship exists for all possible stress paths. Along a K0 stress path the threshold energy, at the limit state, is a linear function of the preconsolidation pressure, i.e. of the vertical effective stress at the limit state. For other stress paths, at a given void ratio, the threshold energy is a function of the stress state at the limit state. Drained creep triaxial tests show that the strain energy is also a good indicator of the creep behaviour of overconsolidated clays. In particular the rate of dissipation of the strain energy is shown to depend essentially on the relative position of the applied effective creep stresses to the limit state surface of the clay. Des essais triaxiaux drainés à contraintes contrôlées sur quatre argiles surconsolidées intactes de l'est du Canada montrent que l'énergie de déformation constitue un bon paramètre de définition de la surface d'état limite de ces argiles. En effet une discontinuité nette de la relation énergie-contrainte se produit sur tous les chemins de contrainte possibles. Le long d'un chemin de contrainte K0, l'énergie limite, à l'état limite, est une fonction linéaire de la pression de préconsolidation, c'est-à-dire de la contrainte effective verticale à l'état limite. Le long d'autre chemins, à un indice des vides donné, l'énergie limite est fonction de l'état de contraintes à l'état limite. Des essais tri-axiaux de fluage drainé montrent que l'énergie de déformation est aussi un bon indicateur du comportement en fluage des argiles surconsolidées. En particulier la vitesse de dissipation de l'énergie de déformation dépend essentiellement de la position relative des contraintes effectives appliquées pendant le fluage et de la surface d'état limite de l'argile.

Experimental study of thermal effects on the mechanical behaviour of a clay

“…They concluded that the contours of total energy, developed along various stress paths, assume shapes similar to those of the limit state surfaces. The study by Tavenas et al [24] shows that the limit state surface does not correspond to a line of equal energy; it seems that the threshold energy is a function of the stress state at the considered location on the limit state surface. Figure 15(d) shows typical results on Kaolin clay in terms of dissipated strain energy during shearing, W : An approximately linear increase of W with respect to the ratio q=p 0 may be seen.…”

The overconsolidation ratio of eemian gyttja determination

“…Tavenas et al (1979), Sridharan et al (1991) and Senol new methods (Senol and Saglamer 2000) are the direct determination methods of preconsolidation pressure, whereas Casagrande (1936), Van Zelst (1948), Schmertmann (1953) and Sällfors methods (1975) are the graphical ones. In this paper, seven of them that utilizes different axes are considered: Casagrande method: e -log(σv') (6) Van Zelst method: ΔH/H -log(σv') (7) Schmertmann method: e -log(σv') (8) log(1 + e) -log(σv') (11) Senol and Saglamer method: …”

Non-Linear Elasto-Plastic Behaviour of Lacustrine Clay

“…Casagrande, 1936;Tavenas et al, 1979) were reviewed by Messerklinger (2001) for use in numerical simulations with elasto-plastic constitutive models. Methods that could be implemented were summarized and it was concluded that the intersection of two straight lines Footnote 4 continued approximating the test results was the best method for evaluating the yield stress, when the data are used for elasto-plastic models.…”