Inelastic Flow Behavior of Argillaceous Salt

The effects of weak clay particles on the creep response of argillaceous salt have been analyzed by considering the particles as damage initiation sites where local tensile stresses and microcracks are induced under triaxial compression. The thermodynamic driving force for the damage process is formulated in terms of an appropriate power-conjucate equivalent stress measure, and the damage kinetics are described in terms of an evolution equation formulated on the basis of the conjugate equivalent stress and the scalar damage variable from Kachanov (1958). This treatment of clay particle effects is then incorporated into the Multimechanism Deformation Coupled Fracture (MDCF) constitutive model. A summary of the constitutive model is presented with an evaluation of the model calculations against experimental data of clean and argillaceous salt. The results suggest that the higher creep rate observed in argillaceous salt compared to clean salt is the consequence of increased damage growth in argillaceous salt due to the presence of weak clay particles.