Ricerc@Sapienza

Convergence of the rotational hardening variable α used in the anisotropic models of clay plasticity, with a constitutively defined attractor/bound αb(η), function of the stress ratio η, under fixed η loading, is analytically investigated. It is analytically shown that depending on various parameters of the rate equation of the evolution of α, such convergence may or may not occur despite the apparent necessity of convergence stemming from the form of the evolution equation of α.

In this work the anisotropic model for clays SANICLAY proposed by Dafalias and Taiebat (2013) is reformulated within the framework of hyper-elastoplasticity. The model, called SANICLAY-T, is fully defined by two scalar potential functions, the free energy and the rate of dissipation. It is first presented in the triaxial space and then generalised in the multiaxial one. The model reproduces exactly the original one for the case of associate flow rule, while leads to a different outcome for non-associated flow.

In this paper, the behaviour of an idealised excavation carried out in a clay sensitive to destructuration is studied through a series of finite-element analyses, employing an advanced bounding surface model developed for structured clays. Several cases are examined, in order to investigate the influence of factors including the velocity of destructuration, the damage produced by the wall construction to the soil-wall contact, the width-to-height ratio of the excavation. The case of a soil deposit insensitive to microstructural damage is also studied for comparison.