Effect of oxygen on damage mechanism and mechanical properties of sandstone at high temperature

The effect of oxygen on the microstructure and mechanical properties of thermally treated rocks is a matter of rock engineering. For comparative analysis, in this study, the sandstone specimens were heated in a vacuum and aerobic environment. It was subsequently subjected to a series of scanning electron microscopy (SEM), P-wave velocity, X-ray diffraction (XRD), and surface colour observation tests. The effect of oxygen on the thermal damage mechanism of sandstone was studied according to the diversities in sandstone microstructure and mineral composition under different heating environments. Then, static and dynamic compression tests were carried out on the heated specimens under different environments; the effect of oxygen on the mechanical properties of sandstone was studied. The results show that the initial temperature of the mineral oxidation reaction was the threshold temperature at which the microstructure, mineral composition, and mechanical parameters of the specimen were heated in different environments to diverge. As the temperature rose, the oxidation reaction of pyrite and chlorite, and related chemical reactions gradually deepened, the thermal damage and mechanical properties of specimens heated in an aerobic environment were more deteriorated than that of the vacuum environment. Therefore, it can be inferred that the oxidation reaction of minerals at high temperatures exacerbated the thermal damage to the sandstone and led to a further deterioration in its mechanical properties. This has important implications for stability analysis of high-temperature rock engineering in aerobic environments.