Experimental study on the dynamic mechanical properties and constitutive model of saline frozen soil

To investigate the mechanical response and energy consumption mechanism of frozen saline clay under dynamic impact loading, experiments were conducted on the dynamic mechanical behavior, failure morphology, and energy dissipation characteristics under different salt contents and impact pressures, and the Johnson‑Cook model was modified. The results show that higher salt content leads to a lower initial slope of the stress‑strain curve, a reduced elastic region, and weaker brittle behavior. The dynamic strength increases with impact pressure but decreases significantly with rising salt content, exhibiting a clear salt weakening effect. For a given salt content, the dynamic strength growth factor increases linearly with impact pressure; under a fixed impact pressure, this factor first increases and then decreases with salt content. Specimens with low salt content mainly exhibit brittle crushing failure; those with medium salt content transition to splitting or shear failure, while high salt content specimens show viscoplastic bulging failure. The incident energy, reflected energy, and absorbed energy stabilize over time, and the absorbed energy decreases with increasing salt content. The energy reflection coefficient increases with impact pressure but decreases with salt content; the energy absorption coefficient decreases with both increasing impact pressure and salt content. Salt content governs the dynamic behavior and failure patterns by controlling the unfrozen water content and ice bonding strength. The proposed modified Johnson‑Cook model effectively predicts the effects of impact pressure and salt content on the strength characteristics of frozen clay.