AN IMPROVED GRAIN-BASED DISCRETIZED VIRTUAL INTERNAL BOND (GB-DVIB) MODEL FOR MODELING MICRO-CRACKING OF GRANULAR ROCKS

The micro-structure of rock essentially affects its macroscopic mechanical behaviors. Based on the grain-based discretized virtual internal bond (GB-DVIB) model, an improved version of the model is developed to investigate the gain-scale, micro-cracking process. Compared with the original GB-DVIB model, a more realistic micro-structure of granular rock is generated by the improved model. A micro-structure generation method is developed to generate different types of mineral grains, grain boundaries, and voids. Based on the relationship between macro- and micro-parameters in the DVIB model, the mechanical parameters of micro-structure obtained by experiments can be employed to calibrate the micro-bond parameters directly. The ability of the improved GB-DVIB model in modeling tensile and compression-shear failure is verified by the simulation of a three-point-bending test and an asymmetric compressive test, respectively. The detailed micro-cracking process of a granite sample is investigated by the simulation of uniaxial compression and tension tests, and the intra-granular and inter-granular cracks both can be reproduced. The simulated results show that the micro-cracks generated in the uniaxial compression test are much larger than the uniaxial tension test. The intra-granular and inter-granular cracks both play important roles in rock compression failure, while the inter-granular cracks play a dominant role in rock tensile failure. For the convenience of the application of the improved GB-DVIB model, the effect of mechanical parameters of micro-structure, grain size, geometric heterogeneity, and porosity on the rock macroscopic mechanical behavior is systematically investigated. Due to the different mechanisms of tension and shear failure, the influence of micro-structure on rock compression and tension failure also varies. The improved GB-DVIB model can effectively generate the micro-structure of granular rock and provides a convenient and effective tool for researching the gain-scale, micro-cracking process of granular rock.