Real-time high-temperature SHPB experimental investigation on dynamic mechanical properties and fracture characteristics of surrounding rock in tunnel fire explosion

This work utilized the SHPB test system and an intelligent box-type resistance furnace to simulate the coupling of real-time high temperature and dynamic load on surrounding rock in tunnel fire explosions. The effects of high temperature and air pressure on the dynamic mechanical properties and fracture characteristics were analyzed. The intrinsic correlation mechanism between the mineral composition and the kinetic characteristics was analyzed via high-precision XRD. The experimental results reveal that the dynamic stress‒strain curves under the coupling of high temperature and impact load can be divided into four stages, namely, the initial, elastic, plastic, and damage stage, without a compaction stage. When the real-time temperature is high, the damage mode of rock transforms from brittle to ductile. The effect of real-time temperature on the internal structure of rock is the key factor influencing its dynamic mechanical properties, macroscopic fracture characteristics, and microscopic mineral composition, and the effect can be divided into a strengthening stage (100 ∼ 300 °C) and a deterioration stage (400 ∼ 800 °C), while high-temperature treatment always results in a deterioration effect. Under real-time high temperatures, the dynamic mechanical properties of rock have obvious temperature effects, and the threshold temperature is approximately 200 °C. Under higher strain rates, the strengthening effect on the dynamic mechanical properties in the early heating process is no longer obvious, but the deterioration effect in the later heating process becomes more significant. This research can provide a certain theoretical basis for evaluating the stability of the surrounding rock in tunnel fire explosions.