Pore fractal and damage characteristics of granite following high-temperature heating and water cooling

Abstract

Investigating the pore structure and damage mechanisms of granite under the synergistic effects of temperature and water is crucial for the development of geothermal resource exploitation strategies. This research conducted mercury intrusion porosimetry, uniaxial compression tests, and acoustic emission analyses on granite samples subjected to high-temperature heating and subsequent water cooling to assess the fractal and damage characteristics of their pore networks. The findings indicate that the pore volume and porosity of granite samples increase progressively after being subjected to high-temperature heating and water cooling, particularly in the development of macropores, whereas the integral dimension of the pore bodies continues to diminish. Furthermore, the failure mode of granite shifts from brittle to ductile, and its uniaxial compressive strength and elastic modulus generally exhibit a declining trend. It was also observed that there exists a strong correlation between the pore volume, porosity, and pore fractal dimension of granite and its mechanical parameters, with the pore fractal dimension showing a positive correlation with the mechanical parameters, and the correlation being most pronounced. Consequently, the pore fractal dimension was established as the characterization variable for microscopic thermal damage, and a granite fractal damage model incorporating pore characteristic parameters and acoustic emission parameters was developed, capable of predicting the extent of rock damage under compression following high-temperature treatment.