Novel Damage Quantification Techniques for Thermal-Treated Granitic Rocks

Analyzing the response of thermally treated granitic rocks is crucial for enhanced geothermal systems (EGS), nuclear waste disposal in deep geological repositories (DGR), and fires in monuments. However, the nature of thermal interaction differs significantly among these processes due to considerable variation in the type of heating source, its energy output, and other geotechnical considerations. In this study, the response of several granitic rocks subjected to heat treatment with rapid cooling was analyzed to quantify the damage using established and novel models. Damage quantification is critical since it appraises the nature of alteration at high temperatures and aids decision-making under vital circumstances such as monument fire. Simultaneous mineralogical and morphological changes within the rock matrix alter the physicomechanical and failure response. Novel damage models based on these properties were developed, analyzed, and compared with the established modulus-based model. While models based on porosity, strengths, and wave velocity render similar results, density and strain-based models do not predict similar damage magnitudes. However, the trend of damage is similar to a modulus-based model. This can be attributed to the degree of susceptibility of a property to high temperature. Since rocks like granite undergo brittle–ductile transformation at high temperatures, various strength-based brittleness indices were calculated and correlated to damage. The damage models and brittleness-based correlations indicate a critical temperature at 400 °C beyond which substantial damage and change in nature of the failure are observed within granites.