| In recent years, with the development of our national economy, the growing demand of iron ore, iron ore resources as industrial raw materials and underground resources in the growth of national economy role become more and more important, but has been the endless mining, also make the underground left a lot of goaf, give people daily life and work brought serious harm.Therefore researching of goaf detection technology is very urgent.The transient electromagnetic method in recent years as the fastest growing and extensive application of time domain induction electric prospecting, its advantage is that high working efficiency, and equipment light, suitable for observation on the ground,is widespread applied in coal detection of mine of mined-out area, but the iron ore in application of the relatively small.This article through to the characteristics of the haze Yuan Jia county, because its terrain ups and downs is larger, the exposed rock more, considering the traditional geophysical exploration methods in this area measurement is difficult to carry out, we choose the transient electromagnetic method for iron ore on the experimental research. First this paper expounds the present situation of the study of mined-out area at home and abroad, summarizes the domestic research on the distribution of the mine, and briefly introduces the development status of the transient electromagnetic method, device types and characteristics.About the positive calculation, in Faraday electromagnetic induction, and on the basis of using maxwell’s equations, first from frequency domain start, the derived, then in Hank transform and cosine transform, draw back line overlap underground transient electromagnetic response formula. In the process of deducing the modeling formula, this paper introduces the displacement current. At present a lot of literatures ignore displacement current, but according to maxwell’s theory that displacement current can also produce magnetic fields, and are made by spin field, displacement current said only the electric displacement flux the rate of change over time, is by changing the electric field produces, no charge for macro directional movement, do not produce the joule heat. Conducted current conductor only flow, and displacement current can exist in a changing electric field existed medium, the conductor and a vacuum. In the medium conducted current is small, displacement current can be very big. So we formulas ignore conducted current.According to the above formulas we conducted a d overlap back line transient electromagnetic modeling simulation, this paper mainly homogenous half the space and shape of the earth three layers of the model, can see, medium dielectric constant, the bigger the transient electromagnetic response, the bigger the inspired the secondary voltage. So much for Yuanjiacun iron ore belongs to infect, iron ore, the dielectric constant is very large (ore> water> air), so the secondary voltage is also stimulate the largest iron ore, water is the second smallest, and minimum air. This is the transient electromagnetic method of detection and data interpretation to provide the basis.The end of the paper, Yuanjiacun iron ore in the practical application area, according to the results of the numerical modeling analysis be explained. Then through the drilling verification and three dimensional space scanning found that explain the scope of mined-out area size, the practical goaf with the basic agreement that transient electromagnetic looking for iron ore goaf good effect.This by transient electromagnetic method in the haze of mined-out area county iron ore experiment on the similar area after mined-out area detection has certain theory and significance. |
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