Abstract: Taking the tailings of Miaogou Iron Mine as the research object，the strength variation law and damage mechanism of tailings cemented body under different cement-sand ratios（1:6，1:8）and slurry concentrations（75%，78%）were systematically investigated by freeze-thaw cycle test. The results show that with the increase of freeze-thaw cycles，the porosity of tailings cement increases significantly，the loss rate of longitudinal wave velocity increases gradually，and the compressive strength and tensile strength show a significant deterioration trend. Among them，the porosity of the sample with a cement-sand ratio of 1∶6 and a slurry concentration of 75% increased to 19.30% after 30 freeze-thaw cycles，and the wave veloci⁃ ty loss rate reached 65%. The sample with low cement-sand ratio（1∶8）showed better damage resistance， and the sample with high slurry concentration（78%）showed lower strength reduction during freeze-thaw cycles. The research results reveal the damage mechanism of freeze-thaw cycle on the macroscopic mechani⁃ cal properties and microstructure of tailings cemented body，which provides a theoretical basis for the engi⁃ neering application of tailings cemented body in cold environment.

Key words: freezing and thawing cycle, porosity, longitudinal wave velocity, compressive strength, ten? sile strength