Experimental investigation of temperature effects on the physical and mechanical properties of red sandstone

With the rapid development of transportation in China, the number of tunnels is also increasing. However, tunnels may be affected by fire accidents during operation, and the surrounding rock will be irreparably damaged by high temperature. To investigate the influence of temperature on the physical and mechanical properties of red sandstone, physical properties were determined and the Brazilian splitting test was conducted on red sandstone after thermal treatment from 25 to 600°C. The results show that with increasing temperature, the apparent colour of the red sandstone gradually deepened. The P-wave velocity and Leeb hardness decreased with increasing temperature, and a typical temperature threshold (300°C) was identified. The tensile strength of red sandstone decreased quickly from 25 to 300°C and then decreased slowly from 300 to 600°C. The acoustic emission (AE) signal shows a high degree of consistency with the stress–time curve. As the temperature increased, the AE became more active, and when red sandstone was near failure, the AE signal increased sharply. The failure mode of sandstone mainly consists of a throughgoing main crack and a secondary crack, and the crack width also grows gradually. Moreover, we observe from polarized light microscopy images that the number of fractures in the sandstone also increases as the temperature rises. The variation of physical and mechanical properties of red sandstone is closely related to microstructure. These findings demonstrate that temperature has an obvious weakening effect on the physical and mechanical properties of sandstone, and provide theoretical guidance and significant engineering information for tunnel fire restoration. Thematic collection: This article is part of the Engineering Geology and Hydrogeology of the Anthropocene collection available at: https://www.lyellcollection.org/topic/collections/engineering-geology-and-hydrogeology-of-the-anthropocene