Study on the effect of micro-geometric heterogeneity on mechanical properties of brittle rock using a grain-based discrete element method coupling with the cohesive zone model

Abstract The micro-geometric heterogeneity has a significant effect on the mechanical behavior and failure mode of brittle rocks. To study the influence of the size distribution and preferred orientation of mineral grains, a statistical grain-based discrete element method coupling with the cohesive zone model is proposed on the basis of the universal distinct element code (UDEC) in this study. First, a mixed-mode cohesive model was developed and implemented in UDEC to simulate the nonlinear behavior of grain interfaces. Then, a micro-parameter calibration procedure based on the Plackett-Burman design, central composite design , and particle swarm optimization was established to reproduce the macro-properties of the Lac du Bonnet granite . Finally, the strength characteristics, deformation response , and failure mode of rocks were numerically examined using the proposed model by varying the size distribution and preferred orientation of mineral grains. The relationship between the micro-geometric heterogeneity and the uniaxial compressive strength , the crack initiation stress, the crack damage stress, the elastic modulus, the Poisson's ratio, and the failure mode of rocks are obtained respectively.