Comparative Study on Mechanical Properties and Crashing Characteristics of Granite After Real-Time High-Temperature and Natural-Cooling

As the mileage of long tunnels and the number of underground engineering projects continue to increase, the issue of rock mass stability after fire and explosion becomes increasingly prominent. Therefore, studying high strain rates mechanical properties of rocks under different heat treatment methods is of great significance to the design of geological engineering. In this study, Caledonian granite of Sejila Mountain is selected as the research object. Impact compression tests are conducted after high-temperature natural cooling and real-time high-temperature treatment to analyze the mechanical properties and crushing energy consumption characteristics after exposure to 400 ℃. The results show that the temperature threshold of Sejila Mountain granite is 800 ℃. On average, the peak stress after natural cooling at 400 ℃, 500 ℃, 600 ℃, and 700 ℃ decreases by 6.96%, 8.77%, 16.11%, and 31.51% compared to room temperature. Under real-time high-temperature, the peak stress decreases by 8.36%, 14.65%, 27.83%, and 46.55% on average compared to room temperature. The specimen fragments under real-time high-temperature are more rounded than those after natural cooling, and the fractal dimension is larger. The specific energy absorption (SEA) has a sudden change critical temperature, which is 500 ℃ for real-time high-temperature and 600 ℃ for natural cooling.