On the mechanical response of anisotropic granular materials

Abstract

<p>The subject of this thesis is the mechanical response of inherently anisotropic granular materials. The study comprises both the experimental and numerical aspects and provides a rigorous methodology for the solution of geotechnical problems involving anisotropic frictional materials.</p> <p>The experimental investigation has been carried out at both the material and structural levels. The material tests involved a series of direct shear, triaxial and hollow cylinder experiments on crushed limestone sand, whose mechanical characteristics are strongly affected by the orientation of the sample. In addition, a scaled foundation setup was designed and a series of experimental tests was carried out to examine the effects of anisotropy on bearing capacity.</p> <p>The numerical part of this work was associated with development and implementation of a constitutive framework that describes the mechanical response of transversely isotropic frictional materials. The framework is based on elasto-plasticity and accounts for the effects of strain localization and inherent anisotropy of both the deformation and strength characteristics. An implicit scheme was proposed for identification of material parameters/functions, which incorporates predictions based on critical plane analysis. As a part of constitutive modeling, a suitable numerical algorithm was also developed to integrate the constitutive equations.</p> <p>The constitutive framework has been implemented in a commercial FE package (ABAQUS). A series of numerical simulations were carried out focused on the assessment of the bearing capacity of a shallow foundation in transversely isotropic granular medium. The results of numerical simulations have been compared with the experimental data. A parametric study was also carried out aimed at examining the influence of various simplifications in the mathematical framework on its predictive abilities.</p>