Multiple-scale fractal features of coal and rock porosity based on image segmentation

According to the importance of the fluid transportation mechanism detail stated by the coal and rock pore system,six coal and rock samples from different mining areas were observed with scanning electron microscope(SEM).The paper proposed a new approach for investigation of multiple scale fractals based on image segmentation.The following segmentation algorithms were employed: the gray level thresholding,the Laplacian edge detector in combination with thresholding,and the Prewitt edge detector to extract,at meso-scale level,the attributes of the fracture configuration,the fracture boundary line,and the attributes of micro-scale pores from SEM image of the coal samples.The fractal dimensions were calculated on the processed SEM images by Box-counting method.The obtained results demonstrate that the lower bound scale at which the self-similarity statistically exists for meso-scale fractures corresponds with 7 500 SEM magnification;the upper bound scale for micro-scale fractures with 2 000 SEM magnification;the fractal dimension of meso-scale fracture configuration represents coals permeability,the fracture boundary fractal dimension expresses irregular level of flow path which is related to seepage resistance,the fractal dimension of micro-fracture is correlated with adsorption and desorption performance.