Study On The Application Effect Of Mine Transient Electromagnetic Technology Under The Metal Interference

Recent years, mine transient electromagnetic technology has been greatlypromoted and applied in each mine of our Country gradually.This largely ensured thesafety of coal production. But in complex geological conditions,metal bodyinterference often becomes the key factor of affecting mine transient electromagneticdetection effect, and there is a lack of systematic study about the effect of detectionunder metal interfenrence. In this paper, the application effect of mine transientelectromagnetic technology under the metal interference were studied throughnumerical simulation, physical model experiments and underground mine test.In this paper, as a thin layer, metal support mathematical model was establishedand the finite difference equations of thin metal layer were deduced.We can concludethe whole space transient electromagnetic response affected by different thickness ofmetal layer through establishing the mathematical model and concluding that theexistence of metal layer slowed the spread velocity and hindered the diffusion rate ofelectromagnetic fields. The result also shows that the metal layer makes the responseof low resistivity anomalies weakened, and it also reduces the sensitivity of TEM.when low resistivity anomalies exists.The categorized simulation of different metal inthe tunnel has been done partly by physical model experiments and underground minetests. When it comes to large metal such as roadheader, it demonstrated thatroadheader and coil cooperates the best when the surface and the front of the coil areparallel. Meanwhile, it interference was the strongest while the response became theweakest when it is Vertical. As the distance between the roadheader and the wireframe get further, the of practical transient electromagnetic field effected byroadheader also get smaller. The optimal backing distance which avoids interferencefrom roadheader was given through many times of applications.For the other metalbody（I-steel,Anchor Net, Track）, metal interference made the sensor signal valuereceived larger and there is a certain relationship between signal strength and thedistance between wireframe and mental body.By contrast with the examples of projects, the paper corrected window resistivityvalue effected by metal of different time series through quoting correction factors.After that, the corrected result was analyzed and it turns out to be good. Finally, somefeasible measures about mental interference and data processing has been proposed.