Study on dynamic mechanical properties and energy dissipation of cyclic impact high temperature bedding sandstone

Abstract

The study of the mechanical properties of bedding rocks at high temperatures is important for deep energy extraction and post-fire tunnel reconstruction. Firstly, the variation rules of apparent color, mineral components, quality, and longitudinal wave speed of bedding sandstone specimens before and after exposure to high temperatures (300°C–1100°C) were studied. Secondly, the cyclic impact test of high-temperature bedding sandstone was conducted using an electromagnetic-driven split Hopkinson pressure bar (SHPB) device. The effects of impact velocity, bedding angle, and temperature on the dynamic characteristics and energy dissipation of sandstone were studied. The results show that the higher the temperature, the darker the apparent color of the rock, the smaller the mass. The wave velocity exhibits a gradual decrease or initially decreases followed by an increase as the temperature rises. The polycrystalline transformation of minerals inside the bedding sandstone occurred after high temperature. The metamorphic temperature of the main mineral crystal quartz is in the range of 500°C∼700°C. As the temperature rises, the peak stress of the sandstone specimens initially exhibits a decrease followed by an increase, reaching a minimum at 900°C. The peak stress may display three distinct patterns in relation to increasing impact number: it may either increase progressively, initially increase and then decrease, or decrease progressively. Unlike sandstone specimens with other bedding angles, the energy absorption of 90° bedding sandstone gradually decreases with increasing temperature. Under cyclic impact loading, the absorption energy is greatest in 90° laminated sandstone, rendering it more susceptible to damage. These results offer theoretical foundation for managing dynamic disasters in deep rock engineering.