Study on the characterization of coal fracture structure and fractal characteristics based on sem and fractal theory

China Coal Technology and Engineering Group Chongqing Research Institute, Chongqing, China

^* Corresponding author: my-cafe@163.com

Abstract

Based on the background of the 2 # coal seam mainly mined in Yulin Mining Area in northern Shaanxi, this paper adopts Scanning electron microscope testing and fractal theory analysis methods, and obtains the fracture size and fractal characteristics of coal samples through the process of sample preparation drying testing analysis.After testing, the cracks in the main coal seam samples in the Yulin mining area in northern Shaanxi show irregular distribution, with small branch cracks mainly derived from larger main cracks, and the width and size range of the main cracks are within 90 μm~617 μm, the width range of branch fine cracks is 0-21 μm.The box counting method was used to analyze the fractal characteristics of surface cracks, and the number of cracks at different fractal scales was obtained. The least squares method was used to calculate the number of cracks N(δ)And grid edge length δ Through regression analysis, it was found that the analysis dimensions of coal seam fractures in the main mining seam of Yulin mining area in northern Shaanxi are between 1.0115 and 1.5082. Based on relevant standards, it is preliminarily determined that the water conductivity of the coal seams in this area belongs to Class IV or Class V,the water conductivity of coal seams is poor,and the difficulty of water permeability is high. This can provide basic support for the application of water injection dust reduction programs in the future.