Dynamic Mechanical Properties and Damage Evolution Behaviors of Ice-Rich Frozen Soil with Various Initial Moisture Contents

To investigate the dynamic mechanical response and damage evolution behavior of ice-rich frozen clay, split Hopkinson pressure bar (SHPB) tests were performed on frozen clay specimens with initial moisture contents of 20%–1,000% under different temperatures, strain rates, and stress states. The stress–strain curves, dynamic strength, peak strain, absorbed energy density, failure mode, and failure progress were studied. The experimental results revealed the following: (1) in the radial-free state, the stress–strain curve of frozen clay with initial moisture contents ranging from 20% to 85% and 1,000% could be divided into three stages: elasticity, plasticity, and failure. In addition, a double peak phenomenon occurs in the stress–strain curves within the initial moisture content range of 120%–480%. (2) In the radial-free state, as the initial moisture content increased, the dynamic strength first increased to a maximum value, then decreased to a minimum value less than the dynamic strength of ice, and eventually increased marginally to the dynamic strength of ice. However, the variation in dynamic peak strain with initial moisture content followed a decrease–increase–decrease three-stage pattern. (3) In the passive confining pressure state, the initial moisture content of frozen soil determined its sensitivity to the confining pressure. (4) The high-speed camera test results indicated that the failure of the ice-rich frozen clay was mainly caused by tensile cracks. The degree of failure of the frozen clay specimens became more evident as the moisture content and strain rate increased. In the passive confining pressure state, the ice-rich frozen clay specimens remained intact except for a small amount of edge peeling.