Research On The Application Of Ground-Air Transient Electromagnetic Method

Ground-air transient electromagnetic method,using ground emission excitation source,air receiving signal working method,combined with the advantages of aviation system and ground system,not only the observed response signal-to-noise ratio is high,but also high work efficiency,and can explore the deep part of the mining area,is an emerging geophysical exploration method.Nowadays,the ground-air transient electromagnetic method has developed rapidly,but there is still not much research on the practical application of the ground-air transient electromagnetic method,which is not conducive to the development of the ground-air transient electromagnetic method.Therefore,on the basis of previous research,this paper studies the application of ground-air transient electromagnetic method in practice,and takes the Huangling area of Shaanxi Province as an example to verify the reliability and superiority of ground-air transient electromagnetic method in complex terrain conditions.First,this paper studies the forward simulation of ground-air transient electromagnetic methods.The forward evolution theory of ground-air transient electromagnetic method of electrical source is briefly described,and the influence of resistivity,flight altitude and offset distance on the electromagnetic response of ground-air transient is discussed.The results show that flight altitude has less influence on transient electromagnetic response.The smaller the resistivity,the later the transient electromagnetic response reaches the late stage;And with the decrease of the offset distance,the corresponding early transient electromagnetic response strength is relatively stronger.The three-dimensional finite element forward theory is briefly introduced,and the three-layer layered model,single anomaly model,double anomaly model,complex anomaly model and single anomaly model under undulating terrain are designed,and the transient electromagnetic response is calculated,and the results show that the transient electromagnetic response multi-track diagram can well distinguish the underground target body.Then,this paper studies and discusses the definition of apparent resistivity of groundair transient electromagnetic methods.The global apparent resistivity definition method of ground-air transient electromagnetic method is briefly described,the apparent resistivity definition of the two-layer model and the third-layer model is described,the apparent resistivity curve is plotted,and the influence of formation resistivity,layer thickness,flight altitude and offset distance on the definition of apparent resistivity is discussed.The apparent resistivity is defined by the three-layer laminar model,single anomaly model,double anomaly model,complex anomaly model and transient electromagnetic response of single anomaly model under undulating terrain,and the apparent resistivity contour cross-section diagram is drawn according to the equivalent conductive plane method to obtain the apparent depth of view by time depth conversion according to the equivalent conductive plane method,and the results show that whether it is a lamellar model or an anomaly model,the resistivity cross-section can well reflect the changes in underground electrical information,and the undulating terrain has little effect on the resolution of underground targets.This provides a basis for the interpretation of ground-air transient electromagnetic data in practice.Finally,this paper conducts field work on the use of ground-air transient electromagnetic devices in Huangling area of Shaanxi Province,and processes the measured data,and draws the apparent resistivity contour cross-sectional view,target coal seam resistivity anomaly plan and three-dimensional resistivity distribution map of some measurement lines according to the global apparent resistivity definition and equivalent conductive plane method,and the results show that the ground-air transient electromagnetic method can clearly reflect the distribution of underground coal seams and the anomaly of high-resistance goaf.This paper verifies the reliability and superiority of ground-to-air transient electromagnetic devices under complex terrain conditions,and provides intuitive data results for the subsequent construction and drilling of coal mines.