DEM (PFC^3D) numerical simulation of the influence of grain orientation on the strength of the Kimachi sandstone

The set of the uniaxial compressive tests of differently oriented specimens of the Kimachi sandstone revealed the significant decrease of UCS values for some orientations of drilled cores. The laboratory obtained descriptions of behavior of Kimachi sandstone were bases for the DEM numerical modeling by means of PFC ^3D. The estimation of material constants of particles contacts models was based on the experimental results of uniaxial loading of rock specimens. The mimicked axial, circumferential and volumetric strains vs. axial stress relationships show good agreement with the experimentally obtained cures. The hypothesis of the possible influence of grain orientation on the strength of the Kimachi sandstone was then evaluated by creating models of specimens consisting of the so called "penny shaped" grains. The orientation of grains seems to prove its contribution in the changes of UCS values. The influence of angle of orientation of "penny shaped" grains can be, however, different for different inclination angle values, from very small decrease to significant drop of strength. Moreover the effect of inclination angle on strength variations is also affected by the confining pressure changes, as it is revealed from results of numerical analysis of conventional triaxial compression tests of models of specimens of Kimachi sandstone.