Study on improving the washing efficiency of heavy metal contaminated clayey soils based on the strong frost heave characteristics of Akadama

The freeze-thaw synergistic chemical washing can remove heavy metal contaminants from clayey soils. However, the intake of eluent is low during the freezing process, resulting in low washing efficiency. In order to improve the washing efficiency, a soil column freeze-thaw washing test was carried out by selecting strong frost heave Akadama soil as the admixture, improving the frost heave of cohesive soil and increasing water migration.. The results indicate that under the same freezing conditions, the frost heave rate of Akadama is 124.48%, with a corresponding increase in frost heave amount and water intake of 5.85 times and 4.82 times that of clayey soils, respectively. This indicates an extremely strong frost heave characteristics. After incorporating Akadama, the frost heave amount and water intake of clayey soils significantly increased, with maximum increments of 130.91% and 113.39%, respectively. After three freeze-thaw cycles, the removal rates of Pb and Cd reached 57.51% and 66.77%, respectively, representing an increase of 173.73% and 113.94% compared to the control group without Akadama incorporation. The method of using Akadama as admixture soil to improve the freeze-thaw and chemical washing efficiency has ease of operability and universality in practical engineering applications, providing a new approach for the remediation of heavy metal contaminated clayey soils in seasonally frozen soil regions.