Dynamic Mechanical Characteristics and Failure Behavior of Precracked Frozen Soil under Impact Loading

Frozen soil contains initial defects such as cracks. In this study, four types of frozen soil specimens are prepared: intact specimens without prefabricated cracks and three precracked specimens with crack angles of 0°, 45°, and 90°. Dynamic compression experiments are conducted using a split Hopkinson pressure bar device to investigate the influence of prefabricated cracks and strain rates on the dynamic mechanical characteristics of frozen soil. The results indicated that the peak stresses of the intact and precracked frozen soil specimens increased with increasing strain rate. Compared with the intact frozen soil specimens, the prefabricated cracks resulted in a significant reduction in the peak stress. The stress distribution at the prefabricated crack boundary was calculated using the Griffith crack model. The dissipated energy is strongly related to the degree of fragmentation of frozen soil. As the dissipated energy increased, the fragmentation became more severe. The fragmentation of frozen soil is strongly influenced by the strain rate but shows insignificant sensitivity to the crack angle. Furthermore, to further reveal the dynamic failure process of the precracked frozen soil specimens, a finite-element model was constructed using ANSYS/LS-DYNA, and the Holmquist–Johnson–Cook model was employed to characterize the dynamic mechanical response of the precracked frozen soil specimens. The corresponding experiments were numerically simulated under experimental conditions. The results revealed that higher strain rates led to more complex crack propagation patterns, and the change in the crack angle affected the final failure mode.