Abstract: Quantitatively characterizing damage in granite under thermal conditions is a significant challenge. This study approaches the issue from an energetic perspective by measuring the temperature during the unsteady-state heat transfer process of granite specimens at elevated temperatures, specifically within the range of 600 °C. The evolution of thermophysical parameters during the regular state stage was systematically analyzed using a cooling method. This investigation explores the characteristics of granite undergoing unsteady state heat transfer, focusing on energy absorption, release, and dissipation. It reveals the intrinsic connection between performance damage and energy evolution laws of granite under thermal action. The findings reveal that granite specimens in different high-temperature states undergo natural cooling in two distinct phases of specific heat change during the regular state stage: steady change and significant change in specific heat. As the initial high-temperature state decreases, the energy dissipated during the whole unsteady state heat transfer process also decreases. In the same cooling mode, the larger the input energy, the larger the proportion of dissipated energy. The amount of dissipated energy in the unsteady state heat transfer process strongly correlates with the deterioration of the macro-mechanical parameters of granite after high-temperature thermal action. The amount of the dissipated energy and the maximum thermal shock factor have a significant linear relationship.

Key words: rock mechanics, unsteady state heat transfer, energy release, energy dissipation, specific heat