Simulation Research On Transient Electromagnetic Devices In Coal Mining Area

There is a wide range of distribution,high damage,and difficult exploration in coal mining area.TEM has become the first choice for coal mine water prevention and control work because of its extremely sensitive to low resistance.At present,there are many researches on transient electromagnetic single devices(In-Loop,coincident loop,fixed-loop,etc.),but there are relatively few comprehensive comparative studies on various devices.Therefore,this study has reference value for the practical application of transient electromagnetic exploration,and it is of great significance for coal mine safety production and water prevention and control work.Starting from the basic theory of TEM,this paper establishes a geological model by using EMIT Maxwell electrical software.By discussing different emission parameters and different parameters of low-resistance anomaly in various devices of TEM,the forward modeling and Inversion analysis,the response characteristics and laws are obtained.1)The transient electromagnetic response value increases withthe increase of the frame(10-100m),but the resolving power of the abnormality(abnormal point response/normal point response)tends to decrease.At 10 m,the resolving power of two devices is basically the same,but with the increase of the frame,In-Loop device has a better resolution ability than coincident loop device;2)The overall response value of transient electromagnetic decreases with the increase of surrounding rock resistivity(200-1000Ω.m),but the ability to resolve abnormalities increases.Moreover,In-Loop device is better than coincident loop device than fixed-loop device;3)The overall response value of transient electromagnetic increases with the increase of the scales of the anomalous body(20-100m),and the resolving power of the three devices to the anomalous body also increases.The effect of In-Loop device and coincident loop device is basically the same,and both are superior to fixed-loop device;4)The overall response value of transient electromagnetic electromagnetic increases with the increase of the thickness of the low-resistance body(5-20m).The resolving power of the three devices to the anomalous body also increases,and In-Loop device is better than coincident loop device than fixed-loop device;5)The overall response value of transient electromagnetic is reduced with the increase of the buried depth of the geometric center of the low-resistance body(80-200m),and the resolving power of three devices to the anomalous body is also reduced,and when the buried depth is small,In-Loop deviceis better than coincident loop device than fixed-loop device,and the detection effect of three devices is close when the buried depth is large.In the Qingxu mining area of Shanxi,a known gob-water was detected by fixed-loop and coincident loop.After inversion and analysis,it is found that the detection effect of coincident loop is better than that of fixed-loop.It shows that the actual situation is basically consistent with the results of the simulation analysis,which proves that the simulation is correct.