(1. School of Civil Engineering，Shenyang Jianzhu University，Shenyang，Liaoning 110168，China；
2. Test and Analysis Center，Shenyang Jianzhu University，Shenyang，Liaoning 110168，China)
Abstract：In order to study the strength characteristics and long-term stability of heavy metal contaminated soil，a series of strength and scanning electron microscope experiments were carried out based on solidified Cu-contaminated soil with magnesium phosphate cement. The freeze-thaw cycle times，magnesium phosphate cement content and copper ion concentration were considered as experiment effect factors，and the strength and microstructure of Cu-contaminated soil solidified were studied under freeze-thaw conditions. The results show that the unconfined compressive strength of solidified soil decreases gradually with the increase of freeze-thaw cycle times and copper ion concentration or the decrease of magnesium phosphate cement content. Under 3 and 12 freeze-thaw cycles，the reduction rate of unconfined compressive strength of solidified contaminated soil is the smallest，and the reduction rate of unconfined compressive strength reaches the peak value when the number of freeze-thaw cycles is 6 to 9 times. The freeze-thaw stability of Cu-contaminated soil of low concentration heavy metal that cured by magnesium phosphate cement is remarkable，and the freeze-thaw stability of solidified soil decreases with the increase of metal ion concentration. The micropore structure of solidified contaminated soil was obtained based on the scanning electron microscope experiment. The content of magnesium phosphate cement increased from 5% to 20%，and the percentage of microscopic statistical pores decreased by 17.43% when the concentration of copper ion was 0.5% and freeze-thawed for 6 times，so the mechanism of strength change is verified. The research provided theoretical and engineering application reference for frozen-thawed areas of northern China to evaluate the long-term stability of solidification treatment of heavy metal contaminated sites.
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2020, Vol. 39 
