The role of transgranular capability in grain-based modelling of crystalline rocks

Considering that many numerical methods have been developed to study the mechanical properties of rocks based on micro heterogeneities such as mineral size, morphology, composition and boundary defects, an overview of grain-based modelling is presented in this study to compare the advantages and limitations of different grain-mimicking methods. Intergranular and transgranular fracturing models and difficulties in parameter calibrations are discussed. Four typical grain models, UDEC-GBM, GB-FDEM, cluster and clump, are used to represent the two main families: block-based grains and particle-based grains with and without considering grain crushing. Subsequently, how grain crushing affects crack stresses, Hoek-Brown strength parameters m(i), localized shearing and cracking transformation is simulated by these grain models. The simulated results indicate that the approaches capable of grain breakage lead to more consistent results in comparison with laboratory tests, for example, evident dilatancy in uniaxial compressive loading, high strength ratios, nonlinear failure strength envelopes and shear bands under high confinement. The role of transgranular capability is significantly important in the simulation of rock deformation using grain models.