Numerical investigation on the failure criterion of normally consolidated clays

In this paper, a series of numerical simulations of conventional laboratory experiments on normally consolidated clays under undrained condition subject to uniaxial compression/extension loading at constant applied rate of strain in axisymmetric and plane strain conditions was performed in rectangular and octagonal modelled specimens in order to investigate failure behaviours of clays. The soil/water coupling finite element technique formulated under finite deformation theory based on the updated Lagrangean scheme were applied for the numerical simulations. Herein, the Cam-clay material with von Mises type failure criterion, which is independent of the Lode angle, is used to describe constitutive behaviour. It can be seen that the stress states at failure of the specimens obtained from the numerical simulations do not show the von Mises shape on the pi-plane but rather more closely resembles the Lade-Duncan model, which is dependent of Lode angle. The result suggests that Lode angle dependence consistently observed in the laboratory at failure is not a constitutive behaviour but is instead a result influenced by applied boundary conditions and material imperfections. Copyright (c) 2006 John Wiley & Sons, Ltd.