Numerical Simulation Of Particle Flow Of Coal Sample Based On Digital Image Processing

At present,in many studies on coal samples,the microstructure of coal has become an important part.The micro-cavity fracture structure of coal is an important factor affecting the gas-liquid seepage performance and storage capacity of coal seam,and plays a decisive role in the analytical adsorption characteristics of coal.The meso-mechanical mechanism of coal sample damage depends not only on the stiffness of coal and mineral itself.Physical properties such as strength are also closely related to the pore fracture structure.In this paper,scanning electron microscopy(SEM)is the main experimental method.Taking four different types of coal samples from four different coal mines as examples,a high-magnification image of the microstructure of coal samples is obtained,and the images are described and analyzed.The surface structure characteristics of coal samples were introduced,and the distribution of coal matrix,mineral impurities and micro-porosity cracks of coal samples under SEM was demonstrated.With the continuous innovation and improvement of digital image processing technology,it has been widely used in geotechnical engineering applications,providing technical support for the understanding and application of the microscopic structure characteristics of coal.In this paper,digital image processing technology is used to image enhancement of the obtained SEM image by Matlab digital image processing software,including gray leveling,contrast enhancement,histogram homogenization and other processes,followed by threshold segmentation and morphology processing.The image is converted into a binary image.Finally,when the processing result is not ideal,the original SEM image is manually simplified,the small area in the image is eliminated,and the small coal sample scatter is filtered out.The final processed image is converted into a vector structure model in CAD format for import into a subsequent particle flow software to generate a PFC numerical model.The establishment of the meso-structural model of coal has a very important role in understanding its mechanical properties.In this paper,the digital image processed SEM image is imported into the PFC particle flow numerical simulation software,and a mesoscopic numerical model is established to meet the structural characteristics and size of the coal sample microscopic image.A numerical model for the coal sample mesostructure PFC is proposed.The method uses a binary image reflecting the structural characteristics of the internal pores of the coal sample,and converts it into a corresponding PFC mesoscopic numerical model corresponding to the surface structure characteristics of the coal sample.Finally,the model is used to carry out the biaxial compression numerical simulation test,and the difference is analyzed.Micro-destructive mechanical properties of coal samples such as coal sample failure morphology,crack propagation and contact force evolution under coal sample,different confining pressures,different monitoring points and different loading rates.It is found that the number of cracks generated by the 4#coal sample is the highest,which can reach 7068;when the axial deviator is at the peak point,the average contact force between the particles reaches the maximum,which is concentrated near 2.2×108 N.The formation of the contact force chail causes macroscopic damage of the coal sample;the confining pressure and loading rate have a certain degree of influence on the simulation results.On the whole,the method proposed in this paper abandons the traditional coal sample mesostructure modeling method and the lack of compiling complex Fish language for modeling,and improves the modeling efficiency and the true accuracy of numerical simulation.The research content is conducive to understanding the internal structural mechanical properties of the material from a nuance,further understanding the disasters such as coal and gas outburst,and ensuring the safe production of coal mines.This method abandons the traditional coal sample mesostructure modeling method and the lack of compiling complex Fish language for modeling,and improves the modeling efficiency and the true accuracy of numerical simulation.The research content is conducive to understanding the internal structural mechanical properties of the material from a nuance,further understanding the disasters such as coal and gas outburst,and ensuring the safe production of coal mines.