Abstract: The compactness of waste residue soil significantly affects its mechanical properties, and it is particularly important to quantitatively analyze the influence of particle gradation on its dry density. The effect of particle size distribution on the dry density of waste slag soil was quantitatively studied by collecting waste slag soil formed by different slag forming methods and conducting particle size distribution and indoor relative density tests. The results show that slag material presents obvious fractal characteristics, with the main gradation curve types being concave and slow S-shaped. Based on the generalized Logistics function and the particle mass fractal model, a two-parameter particle size fractal grading equation is developed. This equation effectively describes the grading characteristics of the waste slag, with parameters a and b adjusting the slope and curvature of the curve. Using the particle size fractal grading equation, the area of the grading curve is integrated, and a prediction model for the extreme dry density of waste slag soil is established. The characteristics of the optimal gradation curve of the waste slag soil and the corresponding parameter range are determined. The research results offer a scientific basis for the stacking design, rolling construction and slope stability analysis of waste slag yards.

Key words: waste slag soil, extreme dry density, particle gradation, fractal theory, compactness