Study on the dynamic characteristics and damage constitutive model of high-temperature bedding sandstone under cyclic impact

To study the dynamic characteristics and dynamic damage constitutive model of high temperature bedding sandstone under cyclic impact, the physical properties of bedding sandstone after high-temperature (300 °C ~ 1100 °C) were studied firstly, and the influence of temperature on the color, mineral composition, quality and wave velocity of bedding sandstone specimens was recorded. Secondly, the dynamic characteristics of high-temperature layered sandstone under cyclic impact were studied by using the split Hopkinson pressure bar (SHPB) device, and the dynamic characteristics of bedding sandstone with different strain rates and impact times were analyzed. Finally, based on the viscoelastic damage element model of bedding rock, a dynamic constitutive model of bedding rock considering high-temperature impact load coupling damage was constructed, and the model were verified by experimental data. The results indicate that, crystallization temperature of the main mineral crystal quartz is between 500 °C and 700 °C. The higher the temperature, the darker the apparent color of the rock, the smaller the mass. As the temperature increases, the wave velocity and the peak stress first decreases and then increases. The temperature causes more damage to the 0° and 45° bedding sandstone, and the damage is most significant at 900 ℃. Under the impact voltage of 1300 V, the peak stress of bedding sandstone increases first and then decreases with the increase of impact times. Impact load makes 0° bedding sandstone more prone to failure after high temperature, while the 45° and 60° bedding sandstone show strong impact resistance. The difference between the model prediction curve and the test curve is small, indicating that the model has good applicability in describing the cyclic impact mechanical properties of high temperature bedding sandstone. The research results can provide a valuable theoretical reference for the prevention and control of rock dynamic disasters in complex deep geothermal engineering environments.