Study on the geometry characteristics of soil primary mineral particles under cryogenic action

Repeated freeze–thaw causes the fragmentation and aggregation of soil particles, which affect particle shape (aspect ratio, roundness, etc.), and this process is a cryogenic weathering process. Changes in soil particle morphology record information about freeze–thaw processes and have the unique characteristics of freeze–thaw traces. To prove this conjecture, four soil specimens were selected in the experiment, and each specimen was studied after 0, 5, 10, 50 and 100 freeze–thaw cycles. The test results show that: Freeze–thaw will change the aspect ratio of particles, and the aspect ratio of particles is mainly distributed between 1 and 4. The particles with aspect ratio of 1.26 are stable and not easy to fragment, and the particles with aspect ratio more than 4 are easy to fragment. The freeze–thaw effect leads to changes in particle roundness, with different manners of change for the four specimens, but all undergo repeated freeze–thaw fragmenting and rounding process. Repeated freezing and thawing can not only lead to fragmentation particle edges and increased particle roundness, but also to fragmentation large-size particles and reduced particle roundness. Compared with the roundness before freeze–thaw and after 100 cycles of freeze–thaw, the coarse sand grains increased the most in roundness, indicating that the large grain size grains showed the most rounding. This study helps to understand the geometric characteristics of soil primary mineral particles under the action of cryogenic environments, and also helps to discern whether the particles have experienced the action of cryogenic environments, which is important for the study of cryogenic soil in cold environments.