Study On Response Characteristic Of Advanced Detection Of Magnetic Source Ground-tunnel Transient Electromagnetic Method

In order to prevent the occurrence of water inrush accidents,roadway(tunnel)excavation process to identify the heading face in front of the hidden geological structure,in advance to take control measures.In view of the advantages of ground transient electromagnetic method and mine transient electromagnetic method,the magnetic source ground-tunnel transient electromagnetic advanced detection technology is proposed to realize real-time dynamic monitoring of tunneling and tunneling.In this paper,the distribution characteristics of the transient magnetic field of the large rectangular source and the basis of the reasonable arrangement of the source are analyzed by theoretical calculation.The response characteristics of the transient electromagnetic field of typical mediated and water structure under ground-tunnel observation method are studied by numerical simulation.The feasibility of the advanced detection of magnetic source ground-tunnel transient electromagnetic method is analyzed.The main results are as follows:(1)The response curve of the induced electromotive force of the ground-tunnel transient electromagnetic method is generally increased first and then descends.With the increase of the observation point depth,the initial value and the extremum are reduced and the time taken to reach the extreme value is prolonged.(2)For the low-resistant anomaly,the initial response value of the induced electromotive force is lower than that of the non-anomalous body,and the response curve reaches the extreme value and then decays,which is greater than the homogeneous half-space response value without the abnormal body.The trend of response to high-resistant anomalies is opposite to that of low-resistant anomalies.(3)In the trapping column model,the amplitude and characteristics of the inductive electromotive force response of the horizontal component y are determined by their horizontal distribution position,the horizontal component x and the vertical component z induced electromotive force are determined by the height of their longitudinal development.Therefore,the general plane position of the collapse column can be determined by the variation of the y component response amplitude,the vertical development of the trapped column is judged by the relative change in the magnitude of the response amplitude of the x and z components.(4)In the model of the goaf area,the horizontal component x and vertical component z magnitude of the response amplitude of the induced electromotive forceis determined by the size of its hydrostatic range,the change of characteristic and amplitude of the horizontal component y induced electromotive force is determined by its spatial horizontal position.So,it is possible to determine the range of the goaf area by the relative change in the magnitude of the response amplitude by the x component and the z component induced electromotive force,the general plane position of the water mined-out area is judged by the variation of the y-component induced electromotive force response curve and the amplitude.(5)In the fault model,the change of the characteristic and magnitude of the response curve of the y component induced electromotive force is mainly determined by its alignment,the horizontal component x and vertical component z of the induced electromotive force response curve characteristics and magnitude of the magnitude are determined by its tendency.Therefore,it is possible to judge the development of the fault by the relative change of the y component response feature and the amplitude,the development of the fault tendency can be judged by the change of the amplitude of the x component and the z component.(6)The field feasibility test of magnetic source ground-tunnel transient electromagnetic advance detection method is carried out in the mine working face of a mine,the results show that this method can be used to detect the guided aquifer structure in the front tunneling face,and the position of the abnormal body can be located by the three-component response of the transient electromagnetic induction.