Mechanical properties of salinized aeolian sand under freeze-thaw cycles

In order to study the mechanical properties of salinized aeolian sand at the edge of the desert in the monsoon freezing zone, triaxial unconsolidated and undrained shear tests were carried out on the aeolian sands with different salt contents under freeze-thaw cycle conditions. To study the stress-strain relationship curves and deterioration laws of shear strengths of aeolian sands with different salt contents after freeze-thaw cycles, a modified Duncan-Zhang model considering the conditions of perimeter pressure and the number of freeze-thaw cycles was proposed. The shear strength deterioration degree was introduced to describe the rate of strength decay of aeolian sand, and the formula for calculating the coupling effect of the number of freeze-thaw cycles and salt content on the shear strength of aeolian sand was proposed. Research results show that the stress-strain curves of aeolian sands with different numbers of freeze-thaw cycles, salt contents, and perimeter pressures are all the strain-softening type. The salinized aeolian sand under freeze-thaw cycles is subjected to the coupling of temperature and salinity, and the strain softening rate of aeolian sand decreases significantly with the increases in the number of freeze-thaw cycles and salt content. The modified Duncan-Zhang model can better characterize the strain softening of aeolian sand. The initial resilience moduli of aeolian sand under different numbers of freeze-thaw cycles increase with the increase in the perimeter pressure, and decrease first and then increase slowly with the number of freeze-thaw cycles. Under the freeze-thaw conditions, the deterioration rate of shear strength of unsalted aeolian sand is slow. In the case of the salinized aeolian sand, the phase changes in the salt and moisture in the soil accelerate the deterioration rate of aeolian sand shear strength, leading to a rapid decrease in the shear strength of aeolian sand. For the aeolian sand under different perimeter pressures, the patterns of strength change are similar, and the shear strengths decrease significantly after the initial freeze-thaw cycle. As the number of freeze-thaw cycles increases, the deterioration rates of strength are gradually stable. The shear strength deterioration degree of aeolian sand increases hyperbolically with the number of freeze-thaw cycles and linearly with salt content.