Abstract: Based on the binary SEM image, a method to express the magnitude of particle congeries area accumulation versus the corresponding area was constructed. Afterward, the definitions of the curvature coefficient and the nonuniformity coefficient of the aforementioned curve were established in order to study the features of the curve for different types of soils. For different area ratios, the proposed method were utilized to discuss the distribution characteristic of particle congeries figured in the SEM photos respectively for Guazhou arenaceous silt and Tianjin clay successfully. The study shows that the area accumulation curves, the curvature coefficients and the nonuniformity coefficients of the silt are significantly different from that of the clay. The curves for the arenaceous silt are smoother than that for the clay and have the trait of the grading curves for the poorly graded soils. Whereas, the curves for the clay exhibit obvious multistep, namely have the feature of grading curves for the soils with certain particle lost. Furthermore, the curvature coefficient and the nonuniformity coefficient of the arenaceous silt are larger than that of the clay. The suggested technique is a new means to evaluate microstructure in soil mechanics and can be employed to quantitatively analyze the difference between SEM images for diverse soils.

Key words: microstructure, arenaceous silt, clay, area accumulation curve, curvature coefficient, nonuniformity coefficient