Uniaxial compression tests on red sandstone specimens after different high-temperature processing and cooling time

High-temperature processing and cooling time significantly affect the rock's physical and mechanical properties, affecting the safety and reliability of high-temperature rock mechanics. Accordingly, this study conducted uniaxial compression tests on the red sandstone specimens after the processing at different temperatures (25–800 °C) and for additional cooling times. It analyzed the effects of the processing temperature and the cooling time on the rock's physical parameters. Moreover, we investigated the relations of the specimen's strength, deformation, and elastic modulus in different samples under different high-temperature processing and cooling periods and examined the sample failure modes drawing the following conclusions based on the present compression test results. First was the effect of high-temperature processing and cooling on the specimen divided into three phases: high-temperature damage, initial cooling, and water absorption metamorphism subjecting the specimen's physical properties to the combined effects of the fracture development degree, water evaporation, adsorption, and the change of the mineral structural components. Secondly, the uniaxial compressive strength and the elastic modulus showed unimodal distribution patterns concerning the coupling action of the processing temperature and the cooling time, while the peak strain almost followed spatial curved surface distribution. Thirdly, the processing temperature imposed a much more significant effect than the cooling time. Finally, the failure mode showed brittle characteristics. After the cooling for three days, the specimen transited from splitting failure to single-level shear failure in terms of failure mode and finally underwent X-shaped conjugate shear collapse. After the processing at 600 °C, the specimen gradually changed from shear to splitting failure with the increased cooling time.