TREATMENT OF ANISOTROPIC DAMAGE DEVELOPMENT WITHIN A SCALAR DAMAGE FORMULATION

This paper is concerned with describing a damage mechanics formulation which provides for nonisotropic effects using a scalar damage variabl e. An investigation has been in progress for establishing the constitu tive behavior of rock salt at long times and low to moderate confining pressures in relation to the possible use of excavated rooms in rock salt formations as repositories for nuclear waste. An important consid eration is the effect of damage manifested principally by the formatio n of shear induced wing cracks which have a stress dependent orientati on. The analytical formulation utilizes a scalar damage parameter, but is capable of indicating the non-isotropic dependence of inelastic st raining on the stress state and the confining pressure. Also, the equa tions indicate the possibility of volumetric expansions leading to the onset of tertiary creep and eventually rupture if the damage variable reaches a critical value.