A new look at rock mechanical behavior from the meso-scale grain

The mechanical behavior of the rock at the macro-scale depends significantly on its granular meso-scale structure as well as properties of each mineral component. Current methods only calibrate the mechanical properties from different macro-scale samples, which certainly introduces limitations to recognize the realistic physics behind rock failure. To address this problem, theoretical analyses of meso-scale mechanics for mineral grains representing the inhomogeneity are studied based on the overall mechanical behavior of the aggregated rock material. Measured porosity and permeability as well as quantitative mineral content from X-Ray Diffraction yields peak patterns are used to build this meso-scale models which are then calibrated with typical laboratory mechanical tests. Through a number of numerical simulations for the uniaxial compression test, the influence of size effect and spatial arrangement of mineral grains on the overall mechanical behavior and failure at the macro-scale sample are analyzed. The macro failure could be attributed to the accumulation and interconnection of the damaged grains. Compared with the results of uniaxial compression tests, numerical results show good agreement, which demonstrates the rationality and accuracy of that novel approach. The proposed methodology may help the operator to estimate rock compressibility and its failure mode under different loadings by merely using micro CT-scan images rather than direct testing in the lab.