It is important to study the effects of the mechanical properties and failure characteristics of defective frozen soil under coupled compression-shear loading for engineering construction safety and disaster prevention. In this study, the particle flow code was used to establish the distinct element method (DEM) model of a split-Hopkinson pressure bar experiment on frozen soil. The failure processes of frozen soils with different tilting angles and holes were simulated using the DEM model to investigate the influence of the tilting angle and hole deviation (deviation from the geometric center of the frozen soil specimen) on the impact mechanical properties and failure characteristics of frozen soil specimens under coupled compression-shear loading. The results of numerical simulation indicated that when the tilting angle and impact strain rate were 0 degrees and 100 s(-1), the axial peak stress of frozen soil specimen with a hole was smaller than that without a hole, the hole deviation had a minor influence on the axial peak stress. When the strain rate was 100 s(-1,) the axial and shear peak stresses of the frozen soil specimen without a hole increased and decreased, respectively, with increasing tilting angle, and the number proportion of shear-cracks also increased. When the tilting angle and strain rate were 60 degrees and 100 s(-1), the fully deviated hole had a minor influence on the impact mechanical properties and failure characteristics of the frozen soil. The impact loading also had a minor influence on the deformation of the hole.

In cold region engineering, the impact of coupled compression-shear loading on frozen soil foundations is a critical issue that urgently needs to be addressed, as it often significantly reduces bearing capacity and can cause structural failures. Accurately characterizing the mechanical behavior of frozen soil under dynamic coupled compression-shear loading is essential for enhancing the safety and stability of cold region engineering projects. This study prepared four frozen-soil specimens with varying tilting angles to investigate failure mechanisms and energy evolution under coupled compression-shear impact loading. The impact-compression experiments were conducted on the specimens under different loading strain rates and temperature conditions using a split Hopkinson pressure bar. The results indicated that the strength of frozen soil was effectively enhanced by higher strain rates and lower temperatures, while it was reduced by increased tilting angle. The fracturing morphology of frozen soil was analyzed from both microscopic and macroscopic perspectives to reveal its failure mechanisms. To quantify the strength characteristics of the frozen soil under various loading conditions, damage variables were defined from an energy-based perspective and incorporated into the Zhu-Wang-Tang viscoelastic constitutive model. Hence, a dynamic constitutive model for frozen soil under coupled compression-shear loading was developed. The model's predictive capability was validated through comparisons with the experimental data, which revealed a high level of agreement. The results of this study provide practical insights into the failure mechanisms and construction design of frozen soil foundations under coupled compression-shear impact loading in cold region engineering.