| Abstract: | A relatively simple yield model is developed for isotropic, porous rocks which yield in a ductile manner. The flow rule and yield function are derived using an adaptation of the work-balance approach of critical state soil mechanics. This adaptation allows for the dissipation of work by frictional and volume change mechanisms, including the dissipation of frictional work at sensibly constant plastic volumetric strain. The yield model uses two material parameters—a basic frictional parameter and a plastic volumetric strain adjustment parameter which is assumed to be constant for the yield locus corresponding to a particular specific volume. The model gives excellent fits to yield loci for two limestones, a chalk and gypsum plaster prepared at different initial void ratios. |
