Abstract: Fractal three-dimensional model has long been used to study soil microstructure. However, the acquisition of parameters necessary for calculating the fractal dimension through conventional geotechnical tests poses challenges, thereby limiting the utilization of fractal theory in soil research. To address this issue, a combined approach integrating three-dimensional processing and triangular grid principle is proposed in this study based on the scanning electron microscope (SEM) testing of undisturbed soil samples collected from Dingbian, Shaanxi Province, and Lanzhou, Gansu Province. This approach enables the calculation of surface area and volume values corresponding to various measurement scales of soil particles (or pores), facilitating the determination of fractal dimensions. The effectiveness and reliability of the proposed method are validated by applying fractal theory to analyzing soil-water characteristics. Moreover, the three-dimensional processing technique allows for the determination of other soil microstructure parameters, such as apparent porosity and specific surface area. Consequently, it can be regarded as a novel method for quantitatively investigating soil microstructure.

Key words: scanning electron microscope(SEM), microstructure, three-dimensional analysis, fractal dimension