Physical-Mechanical Properties of Sandstones After Exposure to High Temperature

Studying the problems of rock engineering under high temperatures has become a new research direction for rock mechanics. The physical-mechanical properties of rocks under high temperatures circumstances have a great interest in many of engineering applications, such as deep geological repositories for heat-generating radioactive wastes, oil/gas recovery enhancement, underground gasification of coals, exploitation of geothermal resources and the protection of buildings against fire or restoration after exposure to fires. In this paper, the physical and mechanical properties of Jiaozuo sandstone after experiencing heat to high temperatures are studied. The temperature varies in a range from 20 °C to 1200 °C. The studied physical properties include the changes of samples' apparent shape, volume, mass, density, and velocity of longitudinal and shear waves through these samples. The studied mechanical properties include peak stress, peak strain, and Young's modulus under uniaxial compression state. The deterioration mechanism of sandstones exposed to high temperatures is briefly discussed by detecting mineral composition. The test results show that high temperature leads to the changes of apparent shape for sandstone, the temperature does not obviously affect the mechanical properties, and heating reinforces some mechanical properties of sandstone in the temperature ranging from room temperature to 400 °C. When the temperature is above 400 °C, the mechanical properties of sandstone present deterioration with the increase of temperature, the peak stress and Young’s modulus of sandstone decrease in different extents. The peak strain of sandstone increases by a big margin before 800 °C. The deformation of sandstone generally increases with the rising of temperature. From 600 °C to 1200 °C, clear brittle-plastic transition appears in sandstone. Sandstone presents plastic failure characteristics after 1200 °C. Thermal stress, changes in mineral formation, and microstructure due to temperature result in changes in mechanical properties and degradation of sandstone.