An energy-based damage model of geomaterials—II. Deductionof damage evolution laws

This paper deals with the establishment of anisotropic conjugate force!based damage evolution laws in the framework of Rice|s "0860# {normality structure|[ Attention is particularly focused on the second!order damage tensors based on the fabric tensor\ which represents preexisting Gri.th microcracks in solids during small deformation\ isothermal and time!dependent processes[ The principal results include the deduced damage surfaces\ potentials and kinetic equations for the basic internal variables\ damage vectors and damage tensor[ For the damage tensor it is shown that the deduced damage surfaces in a.nity space have a parallel relation with the Tresca and Mises yield conditions in stress space and that the damage characteristic tensor J can be determined uniquely by the current damage tensor without resorting to microscopic parameters or unknown empirical coe.cients[