Dynamic Damage Constitutive Model of Frozen Silty Soil with Prefabricated Crack under Uniaxial Load

Defects, such as holes and flaws, greatly affect the mechanical behavior, failure mechanism, and stress wave propagation of frozen soil. To completely characterize the relationship between the dynamic strength and deformation of frozen silty soil containing prefabricated cracks, frozen silty soil specimens with different numbers of prefabricated cracks (zero, one, two, and three cracks) were developed, and dynamic uniaxial compression experiments were performed using the split Hopkinson pressure bar (SHPB) system. The effects of the strain rate and prefabricated crack number on dynamic stress–strain curve characteristics were analyzed. The compound damage variable, which can consider comprehensively the coupling effects of macro- and mesodefects, was calculated based on Lemaitre equivalent strain theory. Two dynamic damage constitutive models were developed and verified based on the conventional Taylor–Chen–Kuszmaul (TCK) and Zhu–Wang–Tang (ZWT) models, and their applicability, advantages, and disadvantages were compared. Strain rate enhancement and prefabricated crack weakening effects were detected for the dynamic compressive strengths of frozen silty soil. It was observed that the two constitutive models essentially could predict the dynamic curves trend under different strain rates and prefabricated crack numbers through a comparison of the theoretical and experimental results. The ZWT model could well reflect the increasing stage compared with the TCK model.