Experimental and Numerical Simulation Studies on the Effects of Freeze–Thaw Cycles on the Mechanical and Permeability Properties of Tailings

Directing its attention on the issue of stability changes in tailings dams under freeze–thaw cycles (FTCs) in permafrost and seasonally frozen ground areas, and considering that tailings are typically used as construction materials for subdams of tailings dams, this study focuses on iron ore tailings. Through triaxial shear tests, computed tomography scanning tests, and permeability tests, the effects of FTCs on the mechanical properties, permeability, and pore structure characteristics of tailings were investigated. Combined with the particle flow code numerical simulation method, the FTC was simulated using a water–particle expansion method incorporating thermodynamic parameters. The mesostructural evolution of the FTC tailings during triaxial shear tests and permeability tests was explored, and the mechanisms of performance degradation were analyzed. The research findings are as follows: (1) The FTC can lead to interpenetration between pores and the formation of new pores, resulting in increased porosity and weakened mechanical properties. (2) There are two main reasons for the deterioration of tailings performance after the FTC: when the number of FTCs is relatively small, the primary cause is particle contact damage; by increasing the number of FTCs, the expansion of pore volume (caused by the volume increase of liquid water upon freezing) becomes the dominant factor. (3) The permeability coefficients of the tailings first increased and then remained stable when the FTC was increased. (4) Compared with conventional methods, the water–particle expansion method–based numerical simulation for FTC tailing seepage better approximated real-world conditions. These findings provide methodological insights for subsequent numerical simulation studies and offer practical recommendations for the design and operational maintenance of tailings dams.