Collapsible Deformation and Microscopic Mechanism of Loess in Seasonally Frozen Soil Region
Seasonal changes and the alternation of day and night produces freeze-thaw cycle effects,which lead to changes in the structure and physical properties of soil in loess areas,and also affected the collapse and deformation characteristics of loess.Indoor collapse tests and microstructure tests were used to analyzed whether the influence of freezing temperature on microstructure was consistent with the response rules of macroscopic collapse deformation.The research results show that:the moisture field and the number of freeze-thaw cycles remain unchange,the collapsing deformation of loess gradually decrease as the freezing temperature decreases.This phenomenon showes that the freezing temperature determines the freezing rate,and the speed of the freezing rate affects the collapsing deformation of loess.As a result,the cementation force between soil aggregates weaken,the skeleton particles deflecte,the particle shape,connection method and distribution arrangement within the soil body changes,and a new stable structure is formed.Quantitative analysis finds that the probability entropy,average shape coefficient,distribution fractal dimension,pore area ratio and pore diameter change range all showed regular changes,which is consistent with the qualitative analysis results.This shows that is a good correlation between the change pattern of pore structure inside the soil and the collapsibility pattern of loess causes by the reduction of freezing temperature.
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