| Mine transient electromagnetic method (MTEM) is a powerful tool for detecting underground water. It is widely used in production and practice, achieving satisfactory results for its convenient and flexible field works. In the dissertation, the whole space field theory inherent in of MTEM was studied in detail. According to the characteristics of coal bearing strata, 1D and 3D geo-electric models were designed to study the numerical simulation of transient electromagnetic field in whole space, focusing on the boundary element method (BEM) simulating the influence of 3D roadway on transient electromagnetic fields in whole space.Based on Maxwell's equations of electromagnetic fields and boundary conditions, two pairs of potential functions were introduced in terms of Coulomb and Lorentz gauges, whose control equations and boundary conditions were deduced as the theory basis of numerical simulation. The transient electromagnetic field in 1D layered medium model was calculated. The solving method of vector potential of vertical and horizontal magnetic dipole source were deduced by method of separation of variables. Circular or quadrate multi-coils are common used as transmitter-receiver in MTEM. Their electromagnetic fields can be got by calculation of line integral of the electromagnetic fields of magnetic dipole. No matter separated loops or coincident loops, the magnetic field in whole space is greater than the field in half space, besides several points in early times. And they have the same attenuation. The theory of half space cannot be well suited to whole space.When the transmitter coils are arbitrarily oriented; the transient electromagnetic field can be seen as the interaction of a VMD and a HMD. Z component of changing rate of magnetic flux is mainly decided by the decomposed VMD, as well as x component of changing rate of magnetic flux by the decomposed HMD. Equivalent circuit method is introduced to visually describe layered medium model system.BEM is used to study 3D roadway model in layered medium. The fundamental solution not only needs to satisfy the control equation, but also needs to satisfy certain boundary conditions at the same time. For 3D roadway model in layered medium, fundamental solutions are the potential functions in terms of Coulomb of layered medium model. The purpose is to use the boundary conditions of the potential functions to eliminate surface integral of infinite interface. It is easy to fit the roadway surface by rule triangular mesh generation algorithm. The algorithm is practical. And the structure of data is simple. Boundary integral equation is discrete by hybrid element method to resolve sketches of corner and edge. A new roadway influence factor was defined to study the influence of roadway on apparent resistivity the same as the definition of roadway influence factor in mine DC prospecting. The roadway influence factor decreases first then increases, and decreases and then increases again in homogeneous medium. When the transmitter-receiver located on floor and roof, the influence is the same. The greater the transmitter-receiver distance is, the greater the roadway influence factor is in earlier times. The roadway influence factor decreases rapidly with time, then keeps steady. The worse the conductivity of surrounding rock is, the smaller the roadway influence factor is. The bigger the physical dimension of the roadway is, the greater the roadway influence factor is. The length of roadway influences more in later times, while the width and height of roadway influences more in earlier times.The influences of roadway in two, three and four layered models were simulated. It is resulted that the apparent resistivity changes greatly because of the roadway. The influence of roadway in layered medium is different from the one in homogeneous medium. The influence of roadway was studied for different geo-electric parameters. Through the integrative analysis of the results, it is known that the apparent resistivity is influenced most by changing geo-electric parameters of the layer contained roadway in all times. Secondly, the apparent resistivity is influenced more by changing the resistivity of direct floor and indirect floor. And the smaller the resistivity of direct floor and indirect floor is, the greater the apparent resistivity changes. At last, the apparent resistivity is influenced smallest by changing the resistivity of roof. Roadway influence factor just changes at the end of the curve. And if the resistivity increases to some degree, the influence changes little.Forward software was explored to modeling 1D and 3D transient electromagnetic fields. COM module was designed to connect Matlab and VB used COM builder contained in Matlab. So the powerful calculated function and graphical display function of Matlab and visual exploited interface were combined fully. The program can work without Matlab environment. The portability was improved greatly. Because the COM module was called by VB, the codes was simplified, the exploited time was reduced and the arithmetic was kept secret. It is man-machine interactive and more convenient to change the parameters of models by visual operated interface.
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