Study on correlation between fractal characteristics and shear strength of bimsoils

Bimsoils are special geological materials between homogeneous soil and fractured rocks. The mixture’s particle geometry and fractal characteristics largely determine their macro-mechanical behavior under external force. The bimsoils can form a series of geological disasters under internal and external geological stress and human engineering activities, triggering some major engineering geological problems and seriously threatening human survival, engineering construction, and safety during operation. This study uses a large-scale indoor direct-shear compression dual-purpose instrument for coarse-grained soil to conduct direct-shear tests on bimsoils with different rock contents (mass percentage). The fractal theory is used to explore the fractal characteristics of bimsoils and establish the correlation between fractal dimension and shear strength and its indexes. Results show that well-graded bimsoils have one-dimensional fractal characteristics, and poorly graded bimsoils have two-dimensional fractal characteristics. In the rock content range of 20% to 60%, as the rock content increases, the smaller the fractal dimension of the rock block is, the greater the shear strength becomes; 60% is the optimal rock content of bimsoils. When the rock content (mass percentage) increases again, the shear strength decreases instead. Under the optimal rock content, the shear strength increases linearly with the fractal dimension of the rock block. The shear strength index value changes synchronously with the shear strength, while the φ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varphi$$\end{document} value remains basically unchanged.