Strength and deformation behavior of snow-sintered ice under coupled cyclic-monotonic loading

The complex failure behavior of ice under cyclic loading holds significant relevance for understanding the behavior of nearshore sea ice cover, ice shelves, and ice pavements or runways. Experimental evidence demonstrates that the strength of freshwater ice, whether in compression or flexure, can either increase or decrease after cyclic loading. To explore this further, new cyclic-monotonic loading experiments were conducted on snow-sintered ice using four-point bending and unconfined compression tests subjected to various temperatures, monotonic strain rates, and cycling conditions. The results show that the average non-cycled flexural and compressive strength of snow-sintered ice at −10 °C is higher than that of water-frozen freshwater ice. The cycled flexural and compressive strength of snow-sintered ice under cyclic loading is highly sensitive to strain rate and accumulated strain. Notably, brittle failure was delayed under cyclic compressive loading at strain rates as high as 10^-1 s⁻¹. However, as the number of cycles increases, accumulated strain leads to a decrease in strength. Cyclic loading altered the ductile-to-brittle transition rate and secant modulus, shedding light on the mechanisms behind high-strain-rate, low-cycle strengthening effects in ice.