"Frostbite effect" of red sandstone under high strain rates

Under the action of negative temperature, the static strength of a rock increases; however, the rock will tend to be brittle, failure strain will decrease, and the rock will also bear the action of internal ice heave force, which leads to complex dynamic behavior of rocks under high strain rate loading. In addition, the geotechnical structures in cold regions are prone to sudden engineering disasters under dynamic disturbance. In this study, a dynamic impact experiment of low-temperature frozen red sandstone was carried out to investigate the temperature effect on the dynamic mechanical properties of red sandstone under high strain rate. Based on the damage theory and energy theory, the effects of different negative temperatures on the strength, damage variables, and energy dissipation of red sandstone were analyzed, and the reasons for the dynamic mechanical strength deterioration of red sandstone at lower negative temperatures were explored using fracture morphology analysis. Research shows that the low negative temperature (after -30℃) can cause a "frostbite" red sandstone, resulting in a sharp decrease in the dynamic mechanical strength of rocks under high strain rate, and transient engineering disasters can easily occur under dynamic disturbance. According to the fracture morphology analysis, the low negative temperature will cause a large number of cracks to be generated at the interface between the components in the red sandstone. The plastic deformation ability of the crack tip is poor, and the crack can easily lose stability and expand under high strain rates, resulting in the low-stress brittle failure. However, due to the complex mineral composition of the cementitious materials, they are more susceptible to negative temperature. Therefore, under the double action of dynamic load and negative temperature, the damage usually occurs first at the cementitious materials and then results in the fracture of the whole red sandstone.