Wojciech T. Sołowski

Equivalent Stress Approach in Creation of Elastoplastic Constitutive Models for Unsaturated Soils

AbstractThis paper introduces an equivalent stress for elastoplastic modeling of unsaturated soils. This equivalent stress unifies various models for unsaturated soils with regard to the stress variables used and allows for a simple separation of the saturated and unsaturated phases of behavior. Moreover, the equivalent stress computed for a given model for unsaturated soil can be used in an existing model for saturated soil so it will gain the ability to model the former. The unsaturated plastic volumetric behavior of the new model is inherited mostly from the parent model for unsaturated soil. The behavior upon shearing depends on both models: the shape of the yield locus is inherited from the original model and the increase of the elastic zone (and possible shift of the elastic zone) from unsaturation depends on the model for the unsaturated soil from which the equivalent stress was taken.

Material Point Method Modelling of Granular Flow in Inclined Channels

The material point method is a novel numerical technique which is especially well-suited to solving problems involving large or extreme deformations. This paper shows the results of the modelling of flow of granular material in inclined channels. During the calculations the granular material is approximated by a Mohr-Coulomb constitutive model. The computed flow is subsequently compared to experimental results published in the literature.

Elastic or Elasto-Plastic: Examination of Certain Strain Increments in the Barcelona Basic Model

The Barcelona Basic Model (Alonso et al. 1990) yield locus has been proven to be non-convex for certain set of parameters (see Wheeler at al. 2002). This paper shows that as this model is formulated in the semi-logarithmic space, the elastic stress path corresponding to a given strain increment is not a straight line. Therefore, the simple assumption that the stress increment is elastic when the stress state is elastic at the beginning and the end of the stress path is no longer correct. The paper examines some strain increments leading to elasto-plastic stress paths which may be easily mistaken for being fully elastic. Some of the stress paths described in the paper can only occur when certain sets of parameters of the Barcelona Basic Model are selected, but others are not dependent on the model parameter set. In the latter case the described mechanism may be relevant to great many other constitutive models which assume a constant shear modulus G and are formulated in the semi-logarithmic space.