Abstract:
Geotechnical engineers have been concerned for many years to determine the conditions under which a geostructure would fail. In order to determine the failure load and the mechanism type, mathematical, constitutive and numerical models have been used. As an example, we can consider the case of a slope subjected to seismic loading. Here, the mathematical model has to describe the coupling between the solid skeleton and the pore fluids. The contributions of Olek Zienkiewicz and Bernardo Schrefler have been of paramount importance for both saturated and unsaturated soils. To describe soil behaviour, constitutive relations are used. We will consider here Generalized Plasticity models for both saturated and unsaturated soils where we have included a state parameter. Regarding numerical models, most of practical cases have been modelled using coupled finite elements. Special techniques have been proposed in the past years to improve the accuracy of the models.
Once failure has been triggered, large deformations and displacements can occur. New mathematical models enlarging the domain of application of the classical pre-failure models have been derived, taking into account large relative displacements between phases. Regarding the rheological behaviour of fluidized soil, the progress has been much slower, and much work lies ahead of the concerned researchers. During last years, we have explored the similarity between rheological models and viscoplastic constitutive equations of Perzyna's type, which seem to provide a suitable bridge between solid and fluidized geomaterials behaviour.
Regarding numerical modelling, lagrangian meshless techniques such as SPH provide a suitable framework. In cases of landslides propagating distances much larger than their initial length, thin layer approximations provide suitable compromises between accuracy and cost of computation.
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