Research on Numerical Simulation and Inversion Technology of Radio Wave Perspective Phase in Tunnels
To increase the accuracy of wireless wave perspective in detecting hidden geological structures in coal seam working faces,upon the phase response characteristics of electromag-netic waves propagation in coal seams,this paper adopts the time-domain finite difference method of electromagnetic waves based on uniform mesh generation method to numerically simulate the propagation of electromagnetic waves.Two types of abnormal models for joints and collapse columns in coal seam working faces are established.Under these two abnormal models,the phase differences of each receiving point in the tunnel are studied,and tomo-graphic imaging is performed on the two abnormal models.The simulation results show that without abnormal bodies,the phase difference of electromagnetic waves in the coal seam changes uniformly,and the slope of the phase difference remains unchanged.When there is an abnormal body,the phase difference between the receiving point and the transmitting point in the tunnel undergoes uneven changes,and the slope of the phase difference changes significantly.When emitting electromagnetic waves at point 10 of the return airway,the phase difference at point 10 of the joint model inlet airway is 11.00 rad,and the phase differ-ence at point 10 of the collapse column model inlet airway is 19.40 rad,indicating that the transmission path of electromagnetic waves and the shape of abnormal bodies affect the phase difference at the receiving point.After inverting the phase constant simulation results of two abnormal models,the inversion position is basically consistent with the initial model posi-tion.The results indicate that the phase constant can be used to detect hidden geological structures in coal seams.
phase constantfinite difference time domainresponse characteristicsjointcollapse columninverting
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