Abstract
Electromagnetic wave penetration coal-rock communication is a significant part for the smart mine communication technology, there are great challenges for electromagnetic wave is rapidly attenuated by factors such as geology and coal seam structure. In order to provide a theory basis for wireless communication technology development in coal rock, based on the Maxwell's equations, this paper establishes a physical model of wireless communication under the conditions of coal seam. To characterize the performance of the electromagnetic wave propagation, we use the Maxwell's equations to derive the exact expression of attenuation coefficient. Also, the parameters of coal and other factors affecting the electromagnetic wave propagation are analyzed and discussed. To further obtain more insights, the attenuation coefficient and skin depth of the very low-frequency (VLF) electromagnetic wave in coal medium with different degrees of metamorphism are studied, as well as the influence of resistivity. This provides scientific theoretical support for the application of VLF communication in coal mines. Finally, our theoretical analyses are verified by computer simulation, and the simulated numerical results show that: 1) The range of frequency of electromagnetic wave suitable for coal medium propagation is 3~3KHz (VLF); 2) The order of the electromagnetic waves attenuation coefficient in coal with different degrees of metamorphism is: anthracite> lignite > fat coal > coking coal > lean coal, and the order of skin depth is: lean coal > coking coal > fat coal> lignite > anthracite; 3) The resistivity of coal has little effect on the attenuation of electromagnetic wave when VLF is used for communication.
Highlights
The wireless communication technology of coal mines is always a hot spots, which has been attracted great interests from coal academia and industry [1]–[3]
The results show that 1) The frequency of electromagnetic wave suitable for coal medium propagation is 3∼3KHz (VLF); 2) The order of the electromagnetic waves attenuation coefficient in coal with different degrees of metamorphism is: anthracite> lignite> fat coal> coking coal> lean coal, and the order of skin depth is: lean coal > coking coal > fat coal > lignite > anthracite; 3) The resistivity of coal has little effect on the attenuation of electromagnetic wave when very low frequency (VLF) is used for communication
Based on the derived formula, the various parameters of coal and other factors affecting the electromagnetic wave propagation are analyzed and discussed, and a physical model of wireless communication under the conditions of coal seam is established. we carry out propagation characteristics analysis for the coal with different degrees of metamorphism through computer simulation
Summary
The wireless communication technology of coal mines is always a hot spots, which has been attracted great interests from coal academia and industry [1]–[3]. When the earth was regarded as the ideal uniform medium and the earth three-layer consumable model, authors in [13] deduced the transmission coefficient and reflection coefficient of electromagnetic waves propagating in the earth It reveals that the low-frequency signal transmission is an important condition for ensuring the reliability of the ground-penetrating communication systems. We establish the physical model of wireless communication in coal medium and analyze the frequency suitable for electromagnetic wave propagation. We simulate the attenuation coefficient and skin depth of the very low-frequency (VLF) electromagnetic wave in coal mediums with different degrees of metamorphism by computer simulation.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
