Abstract: Particle gradation and initial dry density are two crucial factors that influence the strength characteristics of coarse-grained soils. In this paper we aim to quantify the relationship between gradation and initial dry density index of coarse-grained soil and its strength index. Based on the formula process of multiple fractal stages, we derived a quantitative expression, termed as the “skeleton particle density index”, which relates the relationship between the number of particles larger than a certain size per unit volume and the multiple fractal dimensions and dry density. Subsequently, we carried out four triaxial consolidation drainage shear tests on coarse-grained soils with various combinations of gradation and density. The destructive shear stress of continuously graded coarse-grained soil exhibited a linear increase with the skeleton particle density index of the skeleton particle density index. Finally, we conducted extensive literature data verification studies to validate our findings. The obtained results not only provide reference for comparing and selecting optimal schemes for coarse-grained material filling but also offer significant insights into the study of the scale effect on the strength of coarse-grained soils.

Key words: continuous gradation of coarse-grained soil, multiple fractal dimensions, density index of skeleton particle number, large triaxial shear test, shear stress at failure