Research On Response Characteristics Of Surface-to-Underground Transient Electromagnetic Method To Low Resistivity Abnormal Body

Coal is an important basic energy and industrial raw material in China,and water inrush is one of the major disasters encountered in the process of coal mining.Surfaceto-underground transient electromagnetic method(SUTEM)combines the advantages of ground transient electromagnetic and mine transient electromagnetic.It is expected to play an important role in the prevention and control of water damage in coal mine.In this paper,numerical simulation is applied to study the feasibility of surface-tounderground transient electromagnetic detection method in coal mine disaster water source detection.First,the working methods and theoretical formulae of SUTEM are briefly introduced.Then,On the basic of water filled collapse column,crack and fault,the corresponding 3D geoelectric model of low resistivity abnormal bodies are established,and the influences of the low resistivity abnormal bodies on the receiving signal is compared and analyzed,when the low resistivity abnormal bodies are over,under or in the working face.And the influences of the low resistivity abnormal bodies on the received signal under the different positions of the transmission line frame are also analyzed.Through a comparative analysis.The results of the research show that:(1)When the low resistivity abnormal bodies are completely located under the working face,the effect of the low resistivity abnormal bodies on the received signal is very small.When the low resistivity abnormal bodies are completely located over the top of the working face,the influences of the low resistivity abnormal bodies on the received signal in the roadway are mainly concentrated in the ascending segment,and the influences on the descending segment are little.When crossing the working face,the influence of the low resistance abnormal body on the receiving signal not only exists in the ascending segment but also in the descending segment,and the influence in the ascending segment is larger than the above two models.(2)When the low resistivity abnormal bodies is located above the top of the working face,the detection ability of SUTEM to the abnormal body depends on the ratio of the distance between the abnormal body and the transmission line frame and the distance from the receiving point to the transmission line frame,that is,the size of the h/Z,the greater the value of the general h/Z becomes,the stronger the detection ability would be.(3)SUTEM has a great advantage in detecting the low resistivity abnormal body inside the working face,and can accurately locate the low resistance abnormal body inside the working face through two vertical measuring lines.