Discontinuities in the form of cracks or fissures and inclusions are often present in natural clays. They serve as stress concentrators when loads are applied to the material. Such concentrations result in cracks advancing, often surrounded by and preceded by a propagating damage zone. As cracks propagate, the damage may be in the form of one or more shear bands, which may play the part of new stress concentrators and blunt the action of the original crack. This Paper examines some of the phenomena associated with cracks in over-consolidated clays and normally consolidated clays. Differences between isotropic and anisotropic materials, and the level at which serious modifications take place in the fabric of the material are noted. The influence of the cracks and the shear bands on the kinematics and strength of the test specimens is discussed. Des discontinuités sont souvent présentes, sous forme de fractures, fissures et inclusions, dans les argiles naturelles. Elles jouent le rôle de concentrateurs de contrainte lorsque des charges sont appliquées sur le matériau. De telles concentrations se traduisent par une progression des fissures, souvent entourée et précédée par une zone d'endommagement. Lorsque les fissures se propagent, l'endommagement peut apparaître sous forme d'une ou plusieurs bandes de cisaillement qui peuvent jouer le rôle de nouveaux concentrateurs de contrainte et réduire l'action des fissures initiales. L'article étudie quelques uns des phénomènes associésà la fissuration dans des argiles surconsolidées ou normalement consolidées. Des différences entre matériaux isotropes et anisotropes, ainsi que le niveauà partir duquel des modifications importantes apparaissent dans la texture, ont été observés. L'influence des fissures et des bandes de cisaillement sur la cinématique et la résistance des échantillons d'essai est discutée.
The solution of complicated soil engineering and soil structure interaction problems requires the use of realistic constitutive equations and failure criteria. A recent international workshop held at Case Western Reserve University was aimed at assessing the predictive capability of presently available models for granular noncohesive soils. The results of tests conducted on hollow cylinders at Case and on cubes at the University of Grenoble were used to test the various models. This paper highlights some of the realities of soil testing when the equipment used induces different boundary conditions to the soil samples. It evaluates the predictions submitted to the workshop and examines the adequacy of the various classes of models in predicting simple and complicated stress paths using results obtained from standard tests.
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