Numerical simulation research on impact mechanical properties of frozen soil based on discrete element method

Abstract

Many engineering activities have been conducted on permafrost. Frozen soil is subjected to impact loading, particularly during blasting and excavation projects. Thus, it is essential to study the impact mechanical properties of frozen soil. A split Hopkinson pressure bar (SHPB) experiment was conducted to investigate the mechanical responses of frozen soil specimens subjected to impact loading under different strain rates at different temperatures. Evident strain rate and temperature effects were also observed. As crack development in the specimens could not be observed experimentally, a two-dimensional particle flow code was utilized to numerically simulate SHPB impact experiments on frozen soil. A contact bonding model was used for the simulation. We assumed that only temperature could change the particle parameters. The parameters and establishment of the geometric model in the simulation were calibrated and validated by comparing them with the experimentally obtained impact stress–strain curves and wave signals. More influences of strain rate and temperature on crack development were presented intuitively in this study, in combination with the propagation of stress waves. The results of the numerical simulation demonstrated that when the frozen soil specimen was subjected to impact loading, shear failure was the primary failure in the specimen. For a given temperature, a lower strain rate decreased the number of cracks generated, increased the duration of crack generation, and delayed the formation of cracks. For a given strain rate, a lower temperature decreased the number of cracks generated and the duration of crack generation; however, the number of tensile cracks was negligibly affected by changes in temperature.