A study on Bonded Block Model (BBM) complexity for simulation of laboratory-scale stress-strain behavior in granitic rocks

The emergent macroscopic behaviors of Bonded Block Models (BBM) are governed largely by the properties assigned to their three components blocks, contacts and zones (blocks are discretized using finite-difference zones). Over the years, different representations of these components, including elastic/inelastic zones and heterogeneous/homogenous blocks and contacts (corresponding to different mineral grains and associated mechanical properties), have been employed to simulate various aspects of rock behavior. However, there is a lack of understanding of the capabilities of these model representations with respect to their ability to replicate specific rock mechanical attributes. The goal of this study was to test a variety of model representations and evaluate their capabilities in terms of reproducing mechanical behaviors observed for a granitic rock type. It was found that inelastic zones were necessary to capture high confinement peak strengths while incorporation of heterogeneity was necessary to replicate the micro-cracking process. The heterogeneous, inelastic BBMs could match all the calibration targets and is identified as the best representation for modeling the full range of granitic rock behaviors. To help researchers select an appropriate BBM representation for modeling different aspects of rock behavior, a summary table outlining the capabilities of the different model representations is also provided.