Constitutive and computational aspects of localized and diffuse instabilities in geomaterials

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dc.contributor.advisorWan, Richard G.
dc.contributor.authorSouza, Mauricio Pinheiro de
dc.date.accessioned2017-12-18T22:02:52Z
dc.date.available2017-12-18T22:02:52Z
dc.date.issued2009
dc.descriptionBibliography: p. 209-223en
dc.description.abstractA rich variety of failure patterns in geomaterials arise from the instability of otherwise uniform states, stablishing a connection between well-known phenomena such as liquefaction, dilatancy, localization and fracture. While in geotechnical engineering, instability is a misnomer and rather refers to problems of limit equilibrium analysis, by contrast , the notion of instability in mechanics usually refers to two broad categories: material (constitutive) and geometrical (structural). The type of instability discussed in this dissertation is of the material type ince it results from the interaction of particles with their neighbours at the micro cal and has its origins in the strong dependence of material behaviour on strength, density and plastic strain softening. Thus, the proper understanding of material behaviour is essential to the formulation of realistic constitutive models and to the capturing of various failure patterns and instabilities in geomaterials. This dissertation studies failure as a bifurcation problem and discusses localized and diffuse instabilities, the two most ubiquitous types of material instability in geomaterials. These material instabilities are examined through a newly developed elastoplastic constitutive model endow d with appropriate attributes such as strengths, density and fabric dependencies. The analyses reveal the possibility of having diffuse instability in the absence of any localized d formations within the plastic limit surface. The resulting analysis gives rise to the existence of a domain of bifurcation that encompasses the intrinsic effects of stress-strain history , direction of loading, type of loading, and fabric. The computations start at a material point level (mesoscale) and are later on extended to initial boundary value problem settings (macroscale) where both localized and diffuse failures are examined. The boundary value problems involved focus on real geomaterial aspects, such as material heterogeneity and drainage condition. In all simulations, the correlation between nonpositive values of the second-order work and regions of impeding unstable deformation are found to be strong and evident. One of the consequences of such an observation is that conventional analysis of failure based on Mohr- Coulomb plastic limit may not be sufficient to examine the safety of a geostructure. Rather, other criteria such as based on second-order work and the existence of a bifurcation surface within the plastic limit must also be eh eked. As a consequence, FEM-codes need to be equipped with robust constitutive law with softening, non-associated plastic flow along with the second-order work instability criterion to capture the proper physics of material behaviour and the proper failure modes. This dissertation examines contemporary approaches to failure analysis of geomaterial as a bifurcation problem, and hence presents a paradigm shift from current methods of analysis.
dc.format.extentxxiv, 258 leaves : ill. ; 30 cm.en
dc.identifier.citationSouza, M. P. (2009). Constitutive and computational aspects of localized and diffuse instabilities in geomaterials (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/3268en_US
dc.identifier.doihttp://dx.doi.org/10.11575/PRISM/3268
dc.identifier.urihttp://hdl.handle.net/1880/104269
dc.language.isoeng
dc.publisher.institutionUniversity of Calgaryen
dc.publisher.placeCalgaryen
dc.rightsUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.titleConstitutive and computational aspects of localized and diffuse instabilities in geomaterials
dc.typedoctoral thesis
thesis.degree.disciplineCivil Engineering
thesis.degree.grantorUniversity of Calgary
thesis.degree.nameDoctor of Philosophy (PhD)
ucalgary.item.requestcopytrue
ucalgary.thesis.accessionTheses Collection 58.002:Box 1898 520502068
ucalgary.thesis.notesUARCen
ucalgary.thesis.uarcreleaseyen
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