Effects of heating on some physical properties of granite, Shandong, China

Due to the continuous development of underground engineering (underground surrounding rock stability, hot dry rock production, etc.), the thermal damage of granite has attracted much attention. In order to explore the effect of heating up to 800 degrees C on the physical properties, such as mass, color, roughness, wave velocity, thermal diffusivity, and thermal conductivity, of granite in China, the results indicate that the physical properties of granite change significantly with an increase in temperature. The surface roughness, cracks, heat capacity, lightness, and coordinates a* (green-red) and b* (blue-yellow) show a significant increase between 400 degrees C and 600 degrees C. However, the thermal diffusivity, thermal conductivity, and P-wave velocity decrease as the heat treatment temperature increases, especially after 400 degrees C. By using numerical simulation, it is found that the heat transfer in the Luhui granite is affected by the heat treatment temperature and thermal conductivity. When the heat treatment temperature is lower than 500 degrees C, the heat transfer rate increases with an increase in temperature; on the other hand, when the heat treatment temperature is higher than 500 degrees C, the heat transfer rate decreases with an increase in temperature, and 500 degrees C is considered as the critical temperature.