Abstract: The aim of this study is to mitigate the adverse impacts of saline-carbonated soils in the Songhua River and Nenjiang River Plain on engineering and to weaken the damage caused by freeze-thaw cycles on saline-alkali soils in regions of seasonally frozen ground by using lime and fly ash to solidify saline-carbonated soils.The study investigates the effect of different improvement schemes on the shear strength of saline-carbonated soils and their ability to withstand freeze-thaw cycles.The solidification schemes are evaluated using the entropy-weighted TOPSIS model.Results indicate that both lime and fly ash have enhanced the shear strength of saline-carbonated soils.However, the solidification effect of lime is significantly superior to that of fly ash and has transformed the stress-strain curve of saline-carbonated soils into one with strain-softening behavior.Fly ash has distinguished performance in enhancing the resistance of saline-carbonated soils to freeze-thaw damage.The admixture of both lime and fly ash comprehensively accounts for shear strength and resistance to freeze-thaw damage.From the perspective of mechanical properties, freeze-thaw resistance, and economic factors, the optimal solution is the use of 12% lime and 12% fly ash.

Key words: seasonally frozen ground region, solidified saline-carbonated soil, inorganic material, entropy weight - TOPSIS model