Development of micromechanically-based models for geomaterials with coupled multiphysics

点击翻译按钮获取中文摘要

Geomaterials are a class of random heterogeneous materials that are endowed with a rich and complex microstructure involving various phases. As such, coupled transport and mechanical processes of great importance in many contemporary engineering problems can only be effectively analyzed using a micromechanical approach with multiscale modelling. Most current methods of analysis are largely phenomenological, requiring a large number of parameters that lack physical significance. In this proposal, we investigate the instability of an unsaturated soil at low water content where the solid grains interact through a network of water menisci. As the degree of saturation is increased such as in a wetting scenario, the menisci coalesce and develop into a continuous liquid phase. The loss of liquid bridges between grains triggers a microstructural change that leads to a diffuse instability failure characterized by an outburst in kinetic energy. A micromechanical formulation of the above processes is worked out to describe the relative balance between the various forces involved leading to various regimes of material behaviour in a multiphysics setting. Clay-like materials are also studied with proper focus given to short range forces arising from particle electrical charges, given the particle size and ionic solution in the pores. Within this new paradigm of analysis where the physics of small scale phenomena is highlighted and upscaled via mathematical tools such as homogenization, generally accepted concepts relevant to geotechnical practice can be either clarified or amended. The proposed work involves physical, analytical and computational modelling. The gain in resolution in such modelling approach will permit the analysis of many difficult problems such as the swelling behaviour of a protective shale cap layer above a shallow oil sand reservoir under steam and solvent injection for stimulating oil production. Such an analysis will provide crucial information regarding the potential for a blowout and oil leakage to the surface. Another example is the catastrophic collapse failure of unsaturated soil slopes at constant external (gravity driven) loads.