Micromechanics Model for Creep of Anisotropic Clay

Clays frequently possess a fabric with a preferred particle orientation and the creep properties of such clays are therefore anisotropic. A two-dimensional microstructural model to describe this creep response is developed. The model is based on a triangular cell of three particles sliding over each other at a rate predicted by rate-process theory. Equating the rate of energy dissipation within the cell to that of the macroscopic continuum leads to the determination of the tangential viscosity matrix and the matrix of the nonviscous stress components, both of which are stress dependent. The anisotropic creep viscosity parametres then are obtained by a statistical averaging procedure based on the probability density of the particle orientation distribution, as determined by x-ray diffraction. The resulting model is able to predict the directional differences in the creep rate and the stress dependence of creep in clays with anisotropic fabric. Undrained creep tests were conducted on specimens cut in various directions from both isotropically and anisotropically consolidated kaolinite samples.