Study on the degradation mechanism of mechanical properties of red sandstone under static and dynamic loading after different high temperatures

To study the effect of high temperature on the mechanical properties of red sandstone, YNS600 electro-hydraulic servo universal testing machine and pneumatic separating Hopkinson press bar (SHPB) device were respectively used to conduct static and dynamic load loading tests on red sandstone after 500~1000 ℃ action, and X diffraction detection. The damage pattern and mechanical property index changes before and after high temperature action were compared, and the relationship between mineral composition, microstructure and mechanical parameters of the specimens and temperature was analyzed, and a theoretical model was constructed. With the increase of temperature, the peak strength and elastic modulus under static and dynamic loading decreased significantly, and compared with the static stress-strain curve, the dynamic stress-strain curve did not have an obvious compaction phase, and the mass loss rate, volume expansion rate, and longitudinal wave velocity attenuation rate increased above 600 ℃. Minerals such as zeolite and pyrite within the red sandstone specimen gradually reacted after high temperature. The theoretical model explains the degradation mechanism of the mechanical properties of red sandstone under the action of idealized high temperature. The research results can provide a reliable scientific basis for the assessment and prediction of rock engineering after high-temperature fire.