Investigation on physical and mechanical properties of bedded sandstone after high-temperature exposure: Fid-Bau Portal

Investigation on physical and mechanical properties of bedded sandstone after high-temperature exposure

Shi, Xinshuai / Jing, Hongwen / Yin, Qian / Zhao, Zhenlong / Han, Guansheng / Gao, Yuan

Abstract Uniaxial compression tests were carried out on bedded sandstone to explore the effect of exposure to high temperatures on the physical and mechanical properties of the specimens. The influences of testing temperature and bedding orientation on the physical and mechanical properties and failure behaviors of the bedded sandstone were analyzed. The results show that for sandstone with a constant bedding orientation, as the temperature increases, the P wave velocity first increases and then decreases, while the mass and density decrease. The mechanical properties of bedded sandstone, including its compressive strength and elastic modulus, first increase and then decrease with increasing temperature, and a thermal temperature of 400 °C was identified as the transition temperature, above which considerable changes in the mechanical properties were observed. In addition, the P wave velocity, strength, and elastic modulus also varied with increasing bedding orientation, which indicated that the bedded sandstone exhibits anisotropy in its P wave velocity, strength, and elastic modulus. The P wave velocity gradually increases with increasing inclination angle, and the fluctuation in the anisotropic degree of the P wave velocity remains small as the temperature increases. The strength and elastic modulus of the bedded sandstone exhibit U-shaped variations with increasing bedding orientation, and the anisotropy degree first increases and then decreases with increasing temperature. Furthermore, the failure modes are closely related to the designed heat treatment temperature and bedding orientation and can be generally classified into four categories: shearing across the rock matrix and bedding planes, shearing combined with tensile splitting, shearing along the bedding planes, and shearing combined with tensile splitting along the bedding planes. Finally, the effect of high temperatures on the mechanical properties of bedded sandstone was further revealed by means of SEM analysis from a microstructure point of view.