Mechanical behaviour and constitutive model of tailing soils subjected to freeze-thaw cycles

Tailings impoundment located in seasonally frozen soil areas suffers from freeze-thaw cycles (FTC), which has a great effect on the mechanical properties of tailing soils. To study the evolution of mechanical and deformational behaviours of tailing soils experienced FTC, a series of consolidated drained triaxial tests (CD) were performed on the samples experienced various numbers of FTC (N = 0, 1, 5 and 15), and the samples experienced CD tests under N = 0 were reconstituted and then subjected to CD tests again. Besides, the influence of FTC on microstructure and chemical components were also investigated by using of energy dispersive X-ray spectroscopy, powder X-ray diffraction and scanning electron microscopy analysis. The experimental results indicate that the cement failure and the expansion of mean pore size inside tailings are the dominant factors those exert an adverse impact on the mechanical and deformation properties. With the increasing N, the modulus and strength of tailing soils decrease, meanwhile, the trend of volume expansion decreases. In addition, based on the tested results and fractional calculus theory, a fractional order constitutive model was proposed, which provides satisfactory qualitative and quantitative modelling of many important features of tailing soils subjected to FTC.