| The coal is our country's primary energy. The coal production holds the pivotal status in our country national economy. The geological condition of our country's coal mine is complex, the working conditions are bad, the mine roadway up dozens of kilometer long, work scattering of the points, the electromechanical device of the mines and the personnel fluidity is big, the tunnel and the excavation work space of planes is narrow, the environment exists massive air mixtures and so on explosion hazard carbon monoxide, gas and coal dust, the accident potential is enormous. Therefore, establishes the perfect coal mine shaft mobile communication system regarding to enhance the mine pit modern management degree, raises the labor productivity, strengthens the safe guard, safeguards the miner life and the state property security has the very vital significance. In the base of the exiting mine communication, this article author proposed the UHF mailing address is a coal mine shaft communication prioritize direction. Mine roadway in theory will be seen as an ideal waveguide, using finite element analysis methods, analysis the electromagnetic wave propagation characteristics of roadway, and the establishment of mine roadway electromagnetic wave propagation model.The finite element method is one of the numerical calculus method to solve the numeral equation, one kind of powerful numerical calculus tools to solve the project actual problem.It is a numerical analysis technology that union the theory of elasticity, the computational mathematics and the computer software organic synthesis. The finite element method is obtains the approximate solution according to the variational principle and the discretization the method. Its merit lies in the applicable scope to be widespread, may apply in the region boundary line and the internal medium boundary shape complex, as well as the field territory infield distribution change big situation. The finite element method analysis's computation's mentality and the procedure are: Region separate - unit characteristic analysis - establishment equation set - equation set solution.Using the finite element method, regards as the mine pit tunnel the different section shape the perfect waveguide, when analyzes its dissemination characteristic, wave guide's cut-off frequency and the attenuation constant are wave guide's key parameters, their electromagnetic waveguide can effectively play a decisive role in the dissemination. This article needs to solve the subject matter is to analysis the UHF electric wave disseminates when in the coal mine tunnel, and computation the mine pit tunnel's electromagnetic wave dissemination cut-off frequency and attenuation constant in different section shape. This article has analyzed the UHF electric wave's dissemination in rectangular tunnel, circular tunnel and arch tunnel in the same material situation, as well as, when the lateral section size changes, its cut-off frequency and attenuation constant corresponding change rule.The finite element method has many analysis software, the ANSYS software is one kind. This article using the ANSYS software, solves the UHF electric wave's cut-off frequency and the attenuation constant under the different section shape in the mine pit tunnel, and the actual value which and the theoretical value obtained has carried on the comparative analysis, has given the conclusion which intended, corresponded the frequency choice for the mine pit tunnel to lay the foundation. Figure [43] table [14] reference[55]... |
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