Characterization of Fracture Propagation in Granite Under Uniaxial Compression Test Through Digital Image Processing and Discrete Element Method

Abstract

ABSTRACT This study utilized digital image processing (DIP) and discrete element method (DEM) to explore the correlation between mineralogy and fracture propagation in granite. The study concludes that an increase in the content of quartz and feldspar leads to a gradual increase in the uniaxial compressive strength (UCS) value of granite. However, the UCS value of granite undergoes a significant decline with increasing mica content. Additionally, the presence of quartz intensifies the brittleness of granite, while feldspar enhances the ductility of granite. In the isotropic model, fractures tend to initiate from stress concentration points and propagate during the UCS test, causing further stress concentration due to the creation of high-stress zones by the crack tip. In the anisotropic model, fractures usually occur in areas where quartz and feldspar are more concentrated because of a higher likelihood of stress concentration in those regions. However, mica agglomerations are not susceptible to stress concentrations due to their low strength and high toughness, which serve as a buffer. INTRODUCTION Granite is commonly utilized as a host rock for various underground engineering projects such as radioactive waste disposal, deep mining, and enhanced geothermal systems (EGS)(Zhu et al., 2021; Kumari et al., 2017). Nonetheless, the presence of fractures in granite can have varying effects on these projects. In the case of radioactive waste disposal, fractures can compromise the integrity of the repository by providing pathways for radioactive material leakage into the surrounding environment (Jia et al., 2022; Zhao et al., 2022a). Moreover, in deep mining, fractures can pose a significant hazard to miners as they can destabilize the rock mass, leading to rockfalls and collapses that may endanger their lives (Zhao et al., 2022b). Conversely, fractures in granite play a crucial role in EGS, as they facilitate fluid flow and heat transfer. The distribution and connectivity of fractures can impact the efficiency of EGS by affecting the flow of fluid through the reservoir (Zhong et al., 2022).