Study On Calculation Methods Of Apparent Resistivity Of Mine TEM With Multi-Turn Coils

Compared with other geophysical methods, mine transient electromagneticmethod has the advantages of flexible and convenient operations as well as sensitivityfor anomalous bodies with low resistivity. Especially, coincident loop withmulti-minor loops are usually employed to explore different forms anomalous bodieswith containing in the coal mine roadway due to easy to be carried. However, so forthe processing of the data still is using the apparent resistivity formula of central loop.As a result, the values of the processed results are much smaller than is should be, andit differentiate several orders of magnitude compare of the intrinsic resistivity of rock.Hence, it seriously affects the accuracy of interpretation.This thesis theoretically analyzes the conditions of source and physical which canbe used the apparent resistivity formula which is fixed in the instrument. We find themain reason is that original late period field apparent resistivity formula of coincidentloop cannot meet coincident loop with multi-minor loops.On the background homogeneous conductive whole-space, based on the basictheory of Maxwell’s equations of electromagnetic theory, the transmitter loop isdivided into an infinite number of line sources, the whole-space time domainelectromagnetic response of current step off is derived. Then time domainelectromagnetic response of a single line source integral along transmitter loop, getthe transmitter loop at any point P in the receive loop vertical component of themagnetic. Using surface integral considered the magnetic flux change with time in thereceive loop then derivative for time get the value of the induced emf. The off-currentis not the ideal step-off, but rather more complex curve shape. This article is seen asits myopic oblique step off. Using the binary search method for the apparentresistivity values in the new calculation method, avoid doing approximationbrought error in dominance process. And preparation procedures, achieved thecalculate of apparent resistivity with multi-mine turns loops.Similarly, this paper starting from transient electromagnetic response of electricdipole, exporting the electrical source of a long straight wire full space transientelectromagnetic apparent resistivity formula.Finally, with the purpose of verifying the effectiveness of the new calculationmethod, the data of the tank experiments, ground and underground measured areprocessed using the new calculation method. The results show that the sink experiments approach the true value, at the same time, the results of ground andunderground measured data significantly improved.