Dynamic mode I fracture behavior of frozen soil under impact loading and FDEM numerical simulation: Based on a rate-dependent elastoplastic and cohesive model

The dynamic fracture behavior of frozen soil under impact loading is critical for ensuring the structural stability and service safety of infrastructure in cold regions exposed to extreme loading conditions. In this study, impact experiments were conducted on cracked straight-through flat Brazilian disk specimens under varying temperatures (−5, −15, and − 25 °C) and strain rates (100–250 s⁻¹). The crack propagation behavior, mode I dynamic fracture toughness, energy dissipation mechanisms, and responses to temperature and strain rate were systematically investigated. The results indicated that the mode I dynamic fracture toughness of frozen soil increased approximately linearly with strain rate. Low temperatures increased strain rate sensitivity. At high strain rates, the extent of specimen failure and fracture energy increased significantly. Furthermore, a finite–discrete element model incorporating rate-dependent elastoplastic behavior and a cohesive failure criterion was developed to investigate the dynamic fracture behavior of frozen soil. The spatial distribution of the cracks and evolution of the fracture modes at different strain rates were quantitatively analyzed. Simulation results demonstrated that as the strain rate increased from 100 to 250 s⁻¹, the total number of cracks increased exponentially. Shear cracks increased from 7 % to 23 %, whereas tensile cracks decreased from 93 % to 77 %. The initial inclination angle of the central crack significantly affected the fracture modes and propagation paths of the cracks. The numerical simulation results closely matched the experimental observations of crack propagation paths, failure modes, and fracture toughness evolution, indicating that the proposed numerical model effectively captures the dynamic fracture behavior of frozen soil.