Effect of freeze–thaw cycles on the dynamic parameters of modified Na⁺-bentonite by different cations

Bentonites have good application in solid walls, waterproof materials, and landfill cushions, but the cushions of landfills in seasonal frozen regions are susceptible to the effects of freeze–thaw cycles, overhead dynamic loads, and landfill leachate, which can lead to strength change and structural instability. In this paper, the cations in bentonite were exchanged by electrochemical method, and then a series of low-temperature triaxial tests were carried out on the original and modified bentonite. The study evaluated the dynamic characteristics of the different exchange ions under the factors of confining pressures, freeze–thaw cycles, and loading frequencies. The results showed that (1) the electrochemical cation exchange method can effectively replace Na⁺ in the Na⁺-bentonite; (2) under cyclic loading, with increasing shear strain, the shear modulus ratio decreased, and the damping ratio was gradually increased; (3) the dynamic shear modulus ratio increases with the increase of confining pressures and frequencies, and the number of freeze–thaw cycles had little effect on the dynamic shear modulus ratio; and (4) the dynamic parameters of modified bentonite were less affected by external factors and soil’s structure were more stable.