Characterization of Microschist Rocks under High Temperature at Najran Area of Saudi Arabia

Rocks’ physical, mechanical, and mineralogical properties are essential in the design process of underground applications. To understand changes in these rocks’ properties at high temperatures, numerous studies have been conducted on several rock types, with little being known about microschist rock. This paper presents experimental study on the physical (e.g., density and P-wave velocity), mechanical (uniaxial compressive strength (UCS)), and microstructural behavior of microschist rock at room temperature (22 °C) and at high temperatures, i.e., 400, 600, and 800 °C. The results indicated that as the temperature increases, the microschist’s color changed, and dry density decreased by 0.97% at 800 °C. Additionally, the average P-wave velocity of microschist decreased by 4.14, 7.07, and 34.23%, at 400, 600, and 800 °C, respectively. Similarly, at these temperatures, the UCS of the microschist decreased by 34.4, 56.9, and 80.1%, respectively. Further findings from microscopic studies reveal that the observed changes in physical and mechanical properties were due to the structural deformation of the microschist at high temperatures.