The grain-size formation in water/soil science is solely based on the soil characteristics (moisture and minerals) which ultimately determine the sizes of soil grains considering their interactions and surrounding environment. In this study

a methodology was utilized using different approaches (detailed observation

microscopic and macroscopic measurements) to determine loess evolution through time that affected its grain formation and structure. To explore the effect of freeze-thaw damage scale structure of loess environment

the loess Huangling county of Yanan city was taken as the research object with the initial moisture content and the number of freeze-thaw cycles as variables. Through the apparent structure test of scanning electron microscope and CT scanning

with variations of the loess body rate and freeze-thaw cycles

fine structure view and macro features in different initial water contents were explored. Based on Leica Qwin

Canny operator edge detection

fractal dimension

rainbow code pseudo color enhancement technology and saliency theory

the experimental results were analyzed. Testing results showed that with the increase of the number of freeze-thaw cycles

micro structure significantly changed. Specific changes include: particle size becomes uniform

skeleton connection mode changes

surface to surface contact mode changes to point to surface and point to point contact modes

and connection between grains weakens. Microscopic view showed a decrease of high density region and an increase of low density region

and an increase of the frost heaving force. Migration force continues to appear

enabling reduction of the loess body integrity and development of migration channel

which causes increase of ice volume from macro analysis . With the increase of the number of freeze-thaw cycles

surface porosity and fractal dimension increase in the beginning and become stable after 10 cycles. Under freeze-thaw environment

internal micro pores continue to transform into large pores. Enhanced dye technology significantly improves the recognition of CT image. The factors causing alteration of loess grain structure are not only the initial water content and the number of freeze-thaw cycles

but also the interaction (coupling) between water content and freeze-thaw cycles

which has a significant effect on grain structural alteration.