Transient electromagnetic response characteristics of square small coil and its application in geological exploration
Coal mining gradually tends to the deep,while the underground space environment is complicated.In order to optimize the de-tection accuracy and portability of transient electromagnetic method,the finite element calculation method in numerical simulation was analyzed according to the theory of transient electromagnetic method.Forward simulation was used to explore the induced electromotive force response characteristics of the center point of a square transmitting coil with side lengths of 0.5,1.0,and 2.0 m,as well as the transient electromagnetic response characteristics of a receiving coil with a side length of 0.5 m,a diameter of 0.1 m without a magnetic core,and a diameter of 0.1 m with a magnetic core under the excitation of a square transmitting coil with a side length of 0.5 m.By es-tablishing the numerical model of geological structure in advanced detection of roadway driving face,the detection effects of a small square coil with a side length of 0.5 m and a small square coil with a side length of 2.0 m were compared.Taking Daxi Coal Mine as an example,the transient electromagnetic technology of a small square coil with a side length of 0.5 m was applied in engineering prac-tice.The results show that the induced electromotive force variation law of the small square coil device with a side length of 0.5 m is the same as that of the small square coils with side lengths of 1.0 and 2.0 m,but the amplitude is slightly lower;compared to a small square coil with a side length of 2.0 m,it has higher detection accuracy.In engineering practice,the small square coil device with a side length of 0.5 m can effectively explore the rich water area and the geological structure area of the collapse column,proving the reliability of the transient electromagnetic method with a side length of 0.5 m in geological exploration.
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