The mechanical properties and pore structure changes caused by the circulation of low-temperature cooling medium in high-temperature granite are of great significance to further understand the high-temperature rock engineering such as dry hot rock development. Taking Zhangzhou granite as the research object, uniaxial compression tests and micro pore structure tests were conducted to analyze the evolution of different characteristic parameters with the number of cycles, and to explore the degradation mechanism of granite after high-temperature and liquid nitrogen cycling. The experimental results showed that during high temperature and liquid nitrogen cycling treatment, the small pores inside the granite exhibited random and dynamic distribution, while the large pores exhibited widespread distribution. As the number of cycles increased, the nuclear magnetic porosity and peak strain of granite gradually increased, while the compressive strength and elastic modulus gradually decreased. The fracture mode of untreated granite was mainly shear or splitting failure with a single fracture surface, while the fracture mode of granite after high temperature and liquid nitrogen cycling was mainly shear and splitting failure with multiple fracture surfaces. The differences in mineral thermal expansion coefficients and changes in strength and pore structure were key factors inducing damage and deterioration of granite under high temperature and liquid nitrogen cycling.

dry hot rock  /  temperature effect  /  low field nuclear magnetic resonance  /  rock damage