An Experimental Study on the Physical and Mechanical Properties of Granite after High-Temperature Treatment Considering Anisotropy

Abstract

The deep burial disposal of nuclear waste and dry hot rock mining relates to the effects of high temperatures on the physical and mechanical properties of granite. Previous studies have shown that due to the anisotropy of mineral arrangements during granite formation, the physical and mechanical properties of granite vary greatly with different temperatures. We conducted wave velocity tests, optical mirror tests, and uniaxial and conventional triaxial compression tests on granite in three orthogonal directions before and after high-temperature treatment. The main innovative conclusions are as follows: (1) High temperatures can cause the density of thermal cracks in the cross-section of granite, which varies with different sampling directions. Temperatures below 400 °C increase the anisotropy of granite, and there are obvious advantages in the development direction. (2) Under the same temperature conditions, granite samples taken parallel to the dominant direction of cracks exhibit the best mechanical properties. (3) In uniaxial compression tests, granite samples after high-temperature treatment are mostly subjected to tensile splitting failure. When the heating temperature is higher than 400 °C, a large number of transgranular cracks are generated during the thermal damage of granite at this temperature stage. Rock samples taken perpendicular to the dominant direction of the crack can generate radial cracks near the main failure surface, while rock samples taken parallel to the dominant direction of the crack can generate more axial cracks.