Evolution Law of Microcracks in Loaded Granite Based on Discrete Element Method and Two-Dimensional Digital Image Correlation

Granite is widely used in deep underground engineering,high-level radioactive waste disposal,and large-scale rock structures (e.g.,tunnels,slopes and underground storage).Its mechanical properties are closely related to the evolution of internal microcracks.This study proposed a multiscale research method combining two-dimensional digital image correlation (2D-DIC) technology and the discrete element method (DEM).A quantitative identification method for microcrack types in rock-like materials was developed.This method distinguished the micromechanical mechanisms of transgranular and intergranular cracks.The evolution of microcracks in loaded granite was revealed.The results show the proposed crack identification method can accurately distinguish transgranular and intergranular cracks,which provides a reliable analysis tool for studying rock failure mechanisms at the microscale.Compression and tension tests revealed that microcrack propagation depends significantly on the stress path.Under compression,intergranular fractures dominate (approximately 65%),while under tension,transgranular fractures prevail (approximately 63%).The failure mechanisms differ under different stress states.Compression promotes energy dissipation along grain boundaries through multi-directional stress fields,whereas tension leads to transgranular fracture due to a dominant tensile stress field.This study provides new insights for rock damage evolution analysis and offers a theoretical basis for stability assessment in deep rock engineering.