Study on fractal anisotropy characteristics of fracture surface topography of coal and rock under different loading and unloading conditions

Abstract

In order to study the fractal anisotropy characteristics and size effect of coal rock fracture surface under typical failure modes, taking the fracture plane of coal and rock under complex failure load as the research object, laser scanning, CATIA3D model reconstruction and other research methods are adopted to study the fractal anisotropy characteristics and size effect of the fracture plane of coal and rock under complex failure path in combination with fractal theory. The results show that, in terms of the fractal dimension of fracture cross-section trace line, the fractal dimension of the trace line under the complex failure path ranges from 1.001 3 to 1.009 6, and the maximum value is within the range of 30°-90° along the fracture expansion direction. In terms of fractal dimension of fracture section, the maximum fractal dimension of fracture surface destroyed by complex path is concentrated in the range of 120° to 300°. The fractal dimension calculation results of the truncated square fracture section show that, when the side length of the cross-section size is less than 20 mm, the fractal dimension fluctuation range of each typical fracture surface is larger, but when the side length of the selected area is greater than 20 mm, the fractal dimension gradually tends to be stable, and the sectional dimension greater than 20 mm is preliminarily recommended to be adopted when the fractal dimension of the fracture surface is analyzed.

Keywords

• fractal dimension of fracture track line
• fractal dimension of fracture section
• dimensional effect
• fractal theory
• anisotropy
• fracture of coal and rock
• failure modes