Evaluation And Research Of Mine Transient Electromagnetic Advanced Detection Capability

Mine transient electromagnetic(TEM)is now widely used in the prediction and prediction of mine water hazards.Accurate advanced detection can prevent the occurrence of water hazards.The evaluation and research of mine TEM has guiding significance for safe mining of coal mines.This method has the advantages of nondestructive,efficient,portable and flexible,and is sensitive to low resistance body.It has been applied to advanced detection in mines and achieved good results.In this paper,through forward simulation and physical model experiments,the detection capabilities of mine advanced detection,including resolution,limit detection depth,directional detection and penetration depth of transient electromagnetic field,are evaluated and studied.Maxwell software is used to carry out forward simulation and control variable method is used to study the detection ability of TEM to thin layer.By controlling the thickness of thin layer,buried depth ratio and the ratio of resistivity difference to surrounding rock,the detection effect is better when buried depth ratio is 1/10,the detection effect is better when resistivity ratio is less than 1/500,and the detection target body is low resistivity.For the lateral resolution of two anomalous bodies,the main influencing factors are burial depth,resistivity difference and size of anomalous bodies;the transient electromagnetic signal of a single anomalous body is greatly affected by the distance between the measured points and the relative position of the measured points;the longitudinal stratification ability of transient electromagnetic is poor.The detection depth includes the minimum detection depth and the maximum detection depth.The minimum detection depth is affected by the turn-off delay,but does not affect the late signal.The formula of maximum detection depth is deduced theoretically,and the detection distance can reach 96 m ~ 150 m according to the observation parameters of the mine,which can meet the needs of mine detection.Finally,the directional detection of mine transient electromagnetic and the penetration ability of transient electromagnetic field are studied by physical model experiment.When the coil is placed to detect the roof and floor,the anomaly caused by the corresponding position plays a major role.This method is feasible.By presetting the receiving wire frame,it is verified that the secondary induction magnetic field propagates symmetrically upward and downward in a limited distance.The induced eddy current can always be generated by the abnormal body.The propagation distance of the secondary field generated by the eddy current on the abnormal body is limited and independent of the magnetic moment of the transmitting coil.