Influence of freeze-thaw cycle and anisotropy on the dynamic characteristics of undisturbed loess
[Objective]In order to study the effects of freeze-thaw cycle and anisotropy on the mechanical properties and deforma-tion of undisturbed loess in Xining area,[Methods]Freeze-thaw cycle test and semi-sine wave cyclic load dynamic characteristic test were carried out with the help of freeze-thaw cycle test chamber and GDS bidirectional dynamic triaxial apparatus.The modi-fied H-D model was used to analyze the effects of the number of freeze-thaw cycles and the different angles of deposition direction on the dynamic characteristics of loess in Xining area.[Results]The result showed that:(1)With the increase of the number of freeze-thaw cycles,the dynamic shear strength first decreased and then increased.The growth threshold of Gd-1 in loess increased first and then decreased.The loess damping ratio λ firstly increases and then decreases.(2)The dynamic shear strength of soil samples with different angles from the deposition direction is different,that is,from large to small,it is 0°＞60°＞90°＞45°;The Gd-1 growth threshold was 45°＞90°＞60°＞0° from large to small.The loess damping ratio λ is 45°＞90°＞60°＞0° from large to small.[Conclusion]The result show that:(1)With the increase of the number of freeze-thaw cycles,the structural strength and stiffness of the soil showed a trend of weakening first and then increasing,while the kinetic energy consumed by the soil resistance to deformation showed an opposite trend.(2)Anisotropy affects the dynamic shear strength,stiffness and damping ratio of loess.When the soil is 45° from the deposition direction,the soil dynamic shear strength is the lowest,the stiffness is the weakest,and the soil deformation consumes the most kinetic energy.(3)The freeze-thaw cycle affects the mechanical properties of soil in different directions.With the increase of the number of freeze-thaw cycles,the anisotropy of soil is obvious when the deposition direction is 45°,and the structural damage degree is the greatest.
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