The Research On Application Of Ground-airborne Transient Electromagnetic System Based On Loop Source

The ground-air transient electromagnetic method takes into account the advantages of the surface transient electromagnetic method and the airborne transient electromagnetic method,with the characteristics of fast detection rate,high efficiency and strong adaptability to complex environment.It can be predicted that the ground-air transient electromagnetic method will be widely used in the future in the complex terrain exploration.In the past several decades,the ground-air transient electromagnetic system has made great progress in the aspects of device type,forward and inversion theory and so on.However,at present,the ground-air transient electromagnetic is still in the indoor simulation,experimental stage,and is not widely used in the actual exploration.In view of this,the following application studies are carried out:(1)The derivation of forward expression of the ground-air transient electromagnetic method.Based on Maxwell's equations and combining with the electromagnetic response of Kaufman in horizontal layered media,the expression of the vertical induction magnetic field above the layered Earth is deduced by introducing the correlation vector bit.(2)Analysis of response curve of the ground-air transient electromagnetic method.In this paper,the spatial electromagnetic response characteristics of the ground-air transient electromagnetic field under uniform semi-infinite space are studied.The variation characteristics of electromagnetic response curve under different flight altitude,offset distance,launching line frame,transmitting current and resistivity are analyzed,and the optimum sampling area and optimum acquisition parameters of ground-air transient electromagnetic are determined.(3)The construction of the ground-air transient electromagnetic system.According to the actual work needs,the ground-air transient electromagnetic launch system,receiving system,UAV-ground station system and data processing system are assembled.Through field test,it is proved that the launching system can realize high power and high current,low turn-off time,high-precision synchronous,Multi-Band launch.Receiving system can achieve fast,high-resolution acquisition.Ground station-unmanned aerial vehicle system can carry out route planning and design,autonomous flight,flight attitude autonomous adjustment.Data processing system can achieve the flight trajectory,flight attitude reading,and flight acquisition parameters editing and processing.(4)Electromagnetic interference elimination of UAV.The brushless motor and high capacity lithium battery carried by UAV can cause some interference and influence to the data acquisition of the ground-air transient electromagnetic.By collecting and analyzing the electromagnetic interference signals of UAV,the best way to reduce the electromagnetic interference of UAV is to increase the distance between UAV and data system.(5)The design of automatic lifting and leveling device of electromagnetic sensor pod.Aiming at the small angle flight problem of the electromagnetic sensor pod in the air transient electromagnetic receiving system,the automatic lifting and leveling device of the electromagnetic sensor pod is developed.The automatic lifting and leveling device of the electromagnetic sensor pod can realize the automatic lifting and levelling of the electromagnetic sensor pod,thus ensuring the maximum vertical electromagnetic signal collection of the ground-air transient electromagnetic.(6)Ground air transient electromagnetic outdoor flight test.The ground-air transient electromagnetic test and data acquisition test are carried out at different heights.The data collected are analyzed and compared with the forward modeling of layered strata.The results show that the measured ground-air transient electromagnetic response is consistent with the forward model conclusion,which proves the feasibility and accuracy of the ground-air transient electromagnetic system.(7)Ground-air transient electromagnetic fault survey.The fault survey of the ground-air transient electromagnetic system is carried out,and the Flight Survey section and the Seismic exploration section are compared.The results show that the exploration position of the ground-air transient electromagnetic fault coincides with the location of seismic exploration,and the effectiveness of the ground-air transient electromagnetic prospecting system is proved.