Freeze-thaw Deformation of Compacted Sandy Soil in Yinchuan Plain under Closed System

Combined with local engineering geology and climate characteristics,L₉(3⁴) orthogonal test was designed.The freeze-thaw deformation characteristics of compacted sandy soil in Yinchuan Plain under the combined action of compaction,saturation and freeze-thaw cycle were studied by using closed system freeze-thaw test method.The results show that compacted sandy soil with saturation not less than 30%is characterized by frost heave,and the volume increases after freezing and thawing,which is dominated by expansion effect of water freezing.Thaw settlement deformation accounts for a large proportion of the frost heave deformation,being about 80%.The freeze-thaw deformation decreases with the increase of compactness,and increases with the increase of saturation,showing a hyperbolic relationship with the number of freeze-thaw cycles.The joint effect of saturation and compaction is obviously greater than that of any one of the factors,but it is not equal to the simple superposition of the results of the two factors acting alone.Saturation and compaction have significant effects on freezethaw deformation of compacted sandy soil,which are the main controlling factors.In order to alleviate the hazards of freezing and thawing,the compaction should be strictly controlled in the construction of compacted sand engineering,and theincrease of saturation should be strictly prevented in operation.The research results have practical significance for the evaluation and prevention of the frost damage of compacted sand engineering in Yinchuan plain winter irrigation area.