Two-dimensional Freeze-thaw Effects Of Compacted Loess Under Makeup Water Condition

Ningxia is located in the northwest of China,in the middle reaches of the Yellow River,loess is widely distributed,and there are many projects to compact the loess bank slope.The weather in Ningxia is cold in winter,and road and railway embankments,channels and other compacted loess bank slope projects will suffer severe frost damage.At present,there are many studies on the deformation characteristics of loess after one-dimensional unidirectional freeze-thaw and the mechanical properties of soil after freeze-thaw,but there are few studies on the two-dimensional freeze-thaw of loess.Based on this,this paper uses the two-dimensional freeze-thaw test method to maintain the saturation of the sample before and after freezing and thawing with the factors of saturation,compaction and the number of freeze-thaw cycles as the factors to study the two-dimensional freeze-thaw thaw settlement of compacted loess Deformation characteristics,and its shear strength,compressibility,collapsibility,freeze-thaw cycle effects,etc.,analyze the action mechanism and influence law of each factor.The research results provide theoretical and experimental data for the evaluation and prevention of frost damage of the compacted loess bank slope project in Ningxia.Research indicates:(1)As the number of freeze-thaw cycles increases,the height of the sample after freezing increases first and then decreases.The height of the sample after several freeze-thaw cycles is less than the initial height,and the width of the sample increases with the number of freeze-thaw cycles And increase.When the freeze-thaw effect tends to be stable,the frost heave rate,thaw settling coefficient and body deformation rate of the sample increase with the increase of the compaction degree,and increase with the increase of the saturation degree.The body variability showed a homogeneity as the number of cycles of freezing and thawing increased.(2)Under water supplementation conditions,the cohesion and internal friction angle of compacted loess decrease with the increase of freeze-thaw cycles.Before the 2 freeze-thaw cycles,the absolute values of the cohesive force increase and internal friction angle increase caused by the freeze-thaw effect decrease with the increase of the compaction degree and increase with the increase of the saturation;2 times After the freeze-thaw cycle,the absolute values of the cohesive force increase and internal friction angle increase caused by the freeze-thaw effect gradually increase with the increase in the degree of compaction and saturation.After two-dimensional freeze-thaw,the cohesive force and internal friction angle of the sample increase with the increase of compaction degree,and decrease with the increase of saturation degree.(3)The compression coefficient increases as the number of freeze-thaw cycles increases.Before the 2 freeze-thaw cycles,the compression factor increment decreases with the increase in compaction and increases with the saturation;after 2 freeze-thaw cycles,the compression factor increment increases with the compaction And the saturation increases.Compression coefficient decreases as the degree of compaction increases,increases as the degree of saturation increases(4)Compaction of the loess through water replenishment conditions undergoing several two-dimensional freeze-thaw cycles will increase the collapsibility coefficient of the loess.The collapsible coefficient of compacted loess decreases with the increase of compaction degree and saturation.Before 2 freeze-thaw cycles,the increment of the collapsible coefficient caused by the two-dimensional freeze-thaw cycle decreases with the increase of the compaction of the sample;after 2 freeze-thaw cycles,the collapsible coefficient caused by the two-dimensional freeze-thaw cycle The increment increases as the degree of compaction of the sample increases.As the saturation of the sample increases,the increment of the collapse coefficient caused by the two-dimensional freeze-thaw cycle gradually decreases.