A novel grain growth algorithm for grain-based models for investigating the complex behavior of crystalline rock

The mineralogical composition and microstructure of crystalline rock affect its mechanical properties. However, it is challenging to analyze and quantify the associated mechanisms using experimental methods. A potential solution to this problem is to apply microscopic simulation methods, such as a combination of the discrete element method and grain-based model (GBM). A prerequisite for microscopic simulations is to accurately reproduce the microscopic features, especially the interactions between grains. Inspired by the crystallization of polycrystalline rocks, a novel grain growth algorithm that constructs a GBM by simulating the sequential crystallization process is proposed in this paper. The results of comprehensive analyses show that the proposed modeling method can accurately reproduce the mineralogical compositions, euhedral-to-anhedral morphology transitions, and grain size distributions during different crystallization processes. By accurately reproducing the interlocking structure between grains, the proposed method can simulate typical mechanical behaviors, such as the nonlinear strength envelope, uniaxial compressive strength-to-tensile strength ratio, and bimodularity, which are consistent with the experimental findings. The effectiveness of this method in modeling porphyritic structures and grain-scale anisotropic textures is demonstrated, and the microscopic mechanism of fracture mode transition associated with the difference in grain structures is discussed.