Study on the Mechanical Strength Variation and Microscopic Mechanism of Loess in the Ili River Valley Under Freeze-Thaw Cycling Conditions
Addressing the recurring issue of loess landslides in the Ili region of Xinjiang,this study focuses on loess from a natural slope in Xinyuan County,Ili,and leverages the typical seasonal frozen soil characteristics of the region.The research employs indoor triaxial compression tests,scanning electron microscopy,modern image processing,and nu-clear magnetic resonance to investigate changes in macroscopic and microscopic properties of Ili loess under varying freeze-thaw cycles and their correlations.The findings are as follows:①With an increase in the number of freeze-thaw cycles,cohesion in the loess initially decreases,then increases,and eventually stabilizes.The angle of internal friction,on the other hand,generally increases at the outset,decreases subsequently,and gradually stabilizes.②Over the course of freeze-thaw cycles,loess particles continually undergo fragmentation and reaggregation,resulting in complex morpho-logical changes.The number of micropores decreases,while small,medium,and large pores experience slight increases.The arrangement of pores becomes initially complex and eventually simplifies.In summary,the microstructure of Ili loess undergoes a sequence of stabilization,destabilization,and re-stabilization.③ The correlation between particle roundness and cohesion is most pronounced across different freeze-thaw cycle numbers.At the microscale,particle frac-tures and cohesions occur during freezing and thawing,leading to decreased and increased particle roundness,respective-ly.At the macroscale,this translates into structural loosening during freezing,reduced cohesion,and structural densifica-tion during thawing,resulting in increased cohesion.④Particle roundness,particle orientation fractal dimension,and in-ternal friction angle exhibit consistent and robust correlations under varying freeze-thaw cycle numbers.On a microscop-ic level,increasing freeze-thaw cycles lead to a decrease in particle roundness,greater disorder in particle arrangement,and higher particle orientation fractal dimensions.On a macroscopic level,this translates to a disordered particle arrange-ment,an expanded contact area,and consequently,an increased internal friction angle.The results of the study can pro-vide a reference for the investigation of the destabilization mechanism of loess landslides in Yili region and a basis for the calculation of mechanical parameters for the evaluation of the stability of geologic hazards of soil landslides in the seasonal permafrost distribution area of Yili region and the prevention and control of engineering.
Freeze-thaw cyclesLoessmechanical strengthMicrostructureCorrelation analysisIli valley
NETL
NSTL
万方数据
