Study Of Three-dimension Forward Of TEM In Mine

Mine transient electromagnetic method （TEM） is an important minegeophysical methods, compared to ground transient electromagnetic exploration, thismethod has many advantage: small volume effect, high resolution, flexible andefficient equipment, etc. This method is mainly used to predict water and ore bodyinrush structures nearby the roof,bottom and driving face in roadway. And it isincreasingly showing an important role in mine exploration work. But thedevelopment of Mine transient electromagnetic method is severely restricted becauseof relatively backward of explain technology. Therefore, the research ofthree-dimensional(3D) forward modeling for mine transient electromagnetic methodhas important theoretical and practical significance.In this paper, we have not use the method that integrated the response ofmagnetic dipole source in the whole space at first. Actual operating conditions, thewhole area of space for research has been decomposed to three parts: area over theroof of roadway, area under the floor of roadway and air space in roadway.Combined with the appropriate boundary conditions are derived rectangular loopsource once the field equations in three space and frequency domain one-dimensionalforward equations, numerical solution fast Hankel transform background field resultsobtained in the frequency domain and one-dimensional forward modeling results, andverify the correctness. Maxwell integral equations derived secondary field frequencydomain finite difference equations, Yee staggered grid of discrete three-dimensionalstudy of the mine area, combined with the boundary conditions on the secondaryfield is transformed into a large system of linear equations to solve the problem; oflarge-scale numerical linear equations select intends to solve the quasi-minimalresidual(QMR) method, the frequency domain to obtain the full secondary field inthree-dimensional space in the electromagnetic response; finally through the inverseFourier transform and cosine transform the result is converted to the time field results from frequency domain field resultsThe algorithm program which has been programmed by Fortrain languagewas used to various theoretical models in this paper,and use the software: Matlaband surfer was used to plot data of theoretical models. Finally this paper tests theaccuracy of this method by calculating and analyzing the result data of various kindsof models: models of layered space, containing high, low resistivity anomaly.