| Based on the traditional tem,mine tem has been widely used in the prediction and prediction of coal mine disasters.Based on the different geological and electrical characteristics of strata in the coal mine survey area,the transient electromagnetic technique is used to detect and study the low-resistance water-bearing structure distribution in front of the working face roof and floor or roadway head.Mtem usually adopts the single-component detection mode,which can judge whether there is any abnormality but not the specific location of the abnormal body.The multi-component detection model can solve the orientation problem of abnormal body.The study of mine multi-channel transient electromagnetic detection method plays an important role in effectively reducing disasters in coal mines.Therefore,the feasibility of this method is confirmed by numerical simulation,physical simulation and field measurement of multi-channel transient electromagnetic method.(1)The principle of six-channel transient electromagnetic detection is verified by COMSOL electromagnetic module,and numerical simulation experiments of different abnormal body positions are designed.The results of numerical simulation show that the multi-channel transient electromagnetic has the ability to distinguish the orientation of abnormal bodies and improve the detection accuracy.(2)A dual emission-six-channel receiver is designed under the principle of transient electromagnetic response under single-magnetic dipole emission.The transmitting coils of the dual multi-channel transient electromagnetic detection coils are coupled dually with equal and opposite currents.The receiving coils are composed of receiving loops in six different radial receiving directions and receive data in six directions at the same time.The detection depth is affected by coil turns and other factors.(3)According to the multi-channel transient electromagnetic response mechanism simulating transient electromagnetic exploration of roadway,design the cube six channels dual emission model,this model have the ability to judge the abnormal body position,according to determine the induction electric potential in low resistivity anomaly orientation and its depth,and summarizes the model center coil affected by current cut-off effect is smaller.Then,two cylindrical multi-channel dual transmission models are designed.The transmitting coils are in dual transmission mode,and the receiving coils adopt dual receiving and non-dual receiving modes.The influence of different connection modes of the receiving coils on the detection of low-resistance abnormal bodies in different directions and distances is analyzed.Through physical simulation,it can be concluded that multi-channel transient electromagnetic has the ability to judge multiple directions,and it can simultaneously detect coal seam and roof and floor in the roadway.Dual emission has the advantage of judging anomalies before and after the same direction.On the premise of dual transmitting coil,the physical model of dual receiving mode has more sensitive secondary field response and longer detection distance.(4)The dual launch-dual receive mode of three-component model with central loop launch-dual receive mode of three-component model,this paper compares and analyzes dual launch-dual receive mode is verified by the shutoff effect is small,can increase the effective depth and more sensitive in detecting abnormal body characteristics,provide technical guidance for downhole sensor. |
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