Dynamic characteristics and damage constitutive model of saturated frozen granite under cyclic impact loads

Dynamic mechanical characteristics of water-saturated frozen granite under cyclic impact loading were investigated at 10 ℃, 0 ℃, −10 ℃, and −20 ℃ using a Split Hopkinson Pressure Bar (SHPB) apparatus. Key parameters including dynamic strength, strain evolution, fracture morphology, and energy dissipation were quantitatively analyzed under repeated loading conditions. The results indicate that progressive reduction in dynamic strength with increasing impact cycles was observed. Crack development exhibited a transition from initiation to axial penetration, with more severe fracture and wider cracks detected at lower temperatures. Penetration cracks and complete splitting occurred notably at −10 ℃ and −20 ℃, corresponding to enhanced brittleness and reduced dynamic load-bearing capacity. A cumulative damage constitutive model was formulated based on Lemaitre's equivalent strain principle and statistical damage theory. The model captured the temperature-dependent degradation of dynamic stress–strain response, providing accurate representation of damage evolution during cyclic impact at sub-zero conditions.