Study on the influence of mineral composition on the mechanical properties of granite based on FDEM-GBM method

Abstract

The macroscopic mechanical properties and crack propagation of rocks are significantly affected by the micro-scale heterogeneity of rocks. In this study, a two-dimensional tensile/shear fracture model to simulate the nonlinear behavior of grain boundaries through a combined finite-discrete element method based on the grain model (FDEM-GBM). The purpose of this model was to investigate the effects of mineral composition on rock mechanical properties and fracture extension. To calibrate the micromechanical parameters of the cohesive elements within the numerical rock model, the Plackett–Burman design and response surface method were employed. Furthermore, the study analyzed the effects of different mineral compositions on the macro-mechanical characteristics of rocks and attempted to interpret the results from the perspective of fracture evolution. The results demonstrated that the PB design-response surface design-iterative optimization method successfully enabled the calibration of the required microscopic parameters in the FDEM-GBM model. Under uniaxial compression loading, damage primarily occurred inside the crystal, with a dominant mode of tensile failure at the stress peak. Additionally, an increase in feldspar mineral content generally led to a decreasing trend in the uniaxial compressive strength and elastic modulus of the rock model. This changing pattern may be associated with the greater presence of internal cracks within feldspar minerals and relatively fewer cracks in quartz minerals.