Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Final Activity and Management Report Summary - MADUS (Modelling anisotropy and destructuration in unsaturated soils)

In the last few years very significant progress has been made in terms of improved understanding of unsaturated soil behaviour, constitutive modelling of the hydro-mechanical behaviour of unsaturated soils, and the numerical modelling of practical problems. There is, however, still a need to advance in the knowledge and description of unsaturated soil behaviour and associated numerical tools. There are several aspects that need further research as for instance anisotropy, partially saturation, bonding among particles, destructuration and positive dilatancy during strain hardening which are key-features of soil behaviour that cannot be properly described using conventional geotechnical models. In addition, for practical problems anisotropy is especially important for describing the behaviour of compact soils (which are generally compacted in the dry side of the compaction curve) and also for studying some natural anisotropic soils. Despite the relevance of including the effect of all features described before, a little effort has been made up today to model correctly the behaviour of soils.

Many of the recent mechanical models, including the very well know 'Barcelona basic model' (BBM) and other similar models inspired in the BBM, assume that unsaturated soil is an isotropic material. This work presents an extension of the BBM to describe the mechanical behaviour of unsaturated soils with anisotropy, bonding among particles and destructuration. The main mathematical framework also was developed as well as numerical analysis performed to test the performance of the model under different stress paths, with special attention on trajectories involving wetting. A sensitivity analysis of the main model parameters is also presented.

The analysis shows the strong impact that can have the erroneous assumption of isotropic behaviour in unsaturated soils with mechanical anisotropy, bonding and destructuration. Finally, finite element code which incorporates all these features was developed and now can be used as tolls for scientific and technical community.

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