Characteristics of Micro-structure of Warm and Ice-Rich Frozen Soil Improved by Cement and Additives

In permafrost regions, the warm and ice-rich frozen soil (WIRFS) underlying the embankment has a low strength and large compressibility, which threatens the engineering stability. The addition of cement and its additives can improve the mechanical properties of the WIRFS. During the curing and the thawing compression, the micro-structure of the improved WIRFS was changed by hydration reaction and deformation. In this paper, the porosity and directionality of soil were selected as indicators to reflect the variation of micro-structure in the improved WIRFS. Two image processing methods, fuzzy C-means clustering and image segmentation, were introduced to quantitatively calculate the porosity and the directionality of soil particles. The arrangement variation of soil aggregates can reflect the characteristics of micro-structure during the soil improvement. The results indicate that, the addition of cement and additives reduced the directionality of sample before the thawing compression. After the compression, except for the super absorbent polymer, ironic agent, EN-1, Toogood and geopolymer, the addition of antifreeze agent, early strength agent and metakaolin increased the directionality. The average porosity is negatively relevant to the compressibility coefficient. This paper has connected the micro-structure with deformation parameter of the improved frozen soil, which can reflect the improvement mechanism with cement and additives.