Dynamic Mechanical Properties and Constitutive Model of Saturated Frozen Soil with Different Pore Ratios

This study investigates the dynamic stability of frozen soil slopes subjected to strong disturbances such as blasting. Dynamic compression tests were conducted on saturated frozen clay specimens using a split Hopkinson pressure bar system. The effects of strain rate (100–700 s−1), temperature (−15°C, −23°C, and −30°C), and pore ratio (0.30, 0.24, and 0.18) on the mechanical behavior were systematically examined. The propagation of stress waves and the dynamic stress–strain responses were analyzed. Results show that as the strain rate increases, the arrival times of the incident, reflected, and transmitted wave peaks advance, and the time to reach peak energy, stress, and strain decreases. This trend is consistent across all tested temperatures and pore ratios. Both lower temperatures and higher pore ratios lead to increased specimen strength and a marked shortening of the plastic plateau stage in the stress–strain curves. Based on the experimental results and the effective stress principle for saturated soils, a damage-enhanced constitutive model was developed within the Zhu-Wang-Tang constitutive framework by incorporating a wave-impedance term. This term links microstructural changes (ice content and cementation) to macroscopic strength, effectively characterizing the coupled effects of strain rate, temperature, and pore ratio. The model predictions show good agreement with the experimental data, providing a theoretical basis for the dynamic analysis of frozen soil engineering.