Mathematical, experimental, and computational modelling of failure, instabilities, and degradation in geomaterials

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Geomaterials are endowed with a microstructure that makes it difficult to model, but yet interesting to study due to the richness that they display in their stress-strain behaviours. The study of such behaviours shows that the failure of geomaterials is dominated by grain level (microstructural) mechanisms as well as phenomena such as material instability and degradation. For example, material instability in the form of intense inter-granular slip and overriding in sand may lead to the localization of large plastic deformations inside a localized shear band that propagates in the sand mass to ultimately cause a mechanism, and hence failure as seen in landslides. The proposed research develops a multi-scale formulation that penetrates right down to details of grain activity at the meso-scale and back to the macro-scale through a purely micromechanical analysis. The result is a constitutive model that embeds microstructural information, and therefore has a much higher resolution than that offered by continuum plasticity theory. Besides mathematical and numerical developments, the research proposal will also involve extensive physical modelling in concert with numerical modelling for the validation of the proposed theory by using benchmark problems. The end result is a contemporary geomechanics framework within which a computational tool is developed to address, with a high level of confidence, a wide array of geotechnical applications ranging from cyclically loaded bridge abutment walls to geo-structures subjected to geohazards where material instabilities and degradations are clearly precursors to failure.