Dynamic failure behavior and characteristics of frozen soil under coupled compression–shear loading

Frozen soil is inevitably susceptible to complicated impact loads during construction in cold regions, where the coupled compression–shear load is particularly important. In this study, inclined cylindrical samples of frozen soil were employed to conduct coupled compression–shear impact experiments by using a split Hopkinson compression bar with a strain rate varying from 100 to 700 s⁻¹. During the experiments, different compression–shear loading states can be assessed by adjusting the tilting angle of the samples. Furthermore, the Holmquist–Johnson–Cook material model was used to characterize the impact failure behaviors of frozen soil under coupled compression–shear loading using the LS-DYNA software. The results of the experiments and numerical simulations indicated that the strength, failure process, and failure mode of the frozen soil samples exhibited significant strain-rate sensitivity and a certain loading-path dependence. In contrast to the uniaxial impact loading state, the compressive strength was reduced owing to the influence of the shear stress component under coupled compression–shear impact loading. Based on the improved Drucker–Prager criterion, the strength characteristics were reflected on the failure surface, which was featured as a sector and expanded with an increasing strain rate. The inclined samples exhibited coupled tensile–shear failure rather than tensile failure of the right samples (0°) under a high strain rate. In addition, the fragmentation characteristics of frozen soil were closely related to its energy dissipation; with the increase in dissipated energy density, the fragmentation degree of frozen soil deepened.