Experimental Study on the Influence of High-Temperature Treatment on the Pore Structure and Energy Evolution...

To investigate the effect of high temperatures on the mechanical properties and pore structure of sandstone, the compression tests were performed on sandstone specimens subjected to thermal treatments ranging from 25 to 800 °C, with emphasis on analyzing stress responses, acoustic emission characteristics, and energy parameters during failure. Additionally, the evolution of the pore structure in sandstone was analyzed using nuclear magnetic resonance (NMR). The results reveal that exposure to high temperatures compromises the pore structure of sandstone, resulting in an increased prevalence of mesopores and macropores. An upward trend in sandstone porosity is observed as the heat treatment temperature increases. Following high-temperature treatment, the peak stress of sandstone exhibits a declining trend with increasing temperature. Although the accumulative acoustic emission ring counts rise with temperature, the maximum ring count shows a decreasing tendency as the thermal treatment level increases. For sandstone samples subjected to 400 °C treatment, the accumulative acoustic emission ring counts increase with rising temperature, whereas the maximum ring count gradually declines. As the heat treatment temperature increases, both the total energy and elastic energy exhibit a decreasing trend, while the dissipated energy and its proportion relative to total energy progressively increase.