| Analysis of any problem in geomechanics requires statements of equilibrium, kinematics, and the link between stress and strain change, namely the constitutive model. Highly nonlinear and anisotropic stress-strain behavior of geo-materials, from the small-strain region till failure at large strains, makes the use of realistic constitutive models imperative for successful numerical analysis of boundary value problems. The mechanical model of the solid-pore fluid interaction when combined with suitable constitutive description of the solid phase and efficient computational procedures, allows transient and static problems involving deformation to be properly solved.;SANISAND is the name for a class of rigorous constitutive models for sands within the framework of critical state soil mechanics and bounding surface plasticity. In this dissertation a new version of a SANISAND model is introduced which contains a novel constitutive mechanism in order to extend the range of application to any type of constant stress-ratio loading, thus, to realistically capture the plastic strains in a wide range of stress levels, including those sufficient to cause particle crushing. Similarly, SANICLAY is the generic name of a class of clay constitutive models within critical state soil mechanics. In the present work a version of the SANICLAY model is presented which accounts for destructuration mechanism in sensitive clays. To this end in addition to the classical isotropic softening of the yield surface with destructuration, a novel mechanism for frictional destructuration is proposed.;Finally an in-house open source 3D finite element code using OpenSees, UMFPACK and UC Davis Computational Geomechanics Libraries is utilized for implementation of advanced constitutive models in fully coupled dynamic field equations with u-p-U formulation for simulation of solid-pore fluid interaction. The verified and validated methods and models in the resulting numerical tool are used for numerical study of layered soil deposits with spatial variations of density and permeability, which are potentially of primary significance in the development of liquefaction. The presented numerical simulations include capturing of pore pressure -- void ratio redistribution phenomena and demonstrate its potential detriments and benefits in level and sloping grounds. |
