Study On The Ground-tunnel Transient Electromagnetic Method Technology

Nowadays,the mine water inrush accident happens more and more frequently in our country,the demand for detection technologies on hidden water hazard becomes increasingly urgent. Ground hydro-geophysical exploration technology can only be reference of making water-control planning in mining area which has not yet reached the requirements of fine exploration on mine water control. Compared with ground geophysical prospecting,the accuracy of mine geophysical exploration has greatly improved, although several problems still exist. In order to meet the technical demands of fine exploration on mine water control, ground-tunnel transient electromagnetic detecting technology is proposed combined with merits of ground and mine transient technology. It has many characteristics such as strong signal, receiving close abnormal body, strong capacity of coupling, and high resolution.The thesis studies on the methods and theories of ground-tunnel transient electromagnetic technology through methods like theoretical analysis, numerical simulation and physical modeling test. The main idea of this paper including:1. Briefly describes the Ground-Tunnel Transient Electromagnetic detective system.Point out Ground-Tunnel Transient Electromagnetic2. On the basis of Maxwell Equations, has deduced the electromagnetic field component expression of Ground-Tunnel Transient Electromagnetic; basing on Hankel and Cosine transformation system, has studied the computing method of electromagnetic field in roadway space, and using first-order approximation of Bessel function to turn double Bessel function into single Bessel function, has realized the calculation of any arbitrary point of the electromagnetic field component.3. It verifies the correctness of definition and the feasibility of calculation method by using one dimensional model trial. Establish a simple one dimensional model, which simulates and calculates the response characteristics of the magnetic field component in the time domain and with the offset distance. The result shows that, in the early stage, the transient electromagnetic field was gradually spread from shallow to deep, from the edge of the loop to the center; while in the late stage, the transient electromagnetic filed in the whole diffusion area tends to be uniform in vertical direction.4. Based on the diffusion equation of Transient Electromagnetic of rectangle transmitter loops, has written a staggered grid finite difference time domain program of Ground-Tunnel Transient Electromagnetic, has conducted three-dimensional numerical simulations of regular and Ground-Tunnel Transient Electromagnetic and has analyzed the response that Ground-Tunnel Transient Electromagnetic makes to low-resistance abnormal bodies. The results indicate that the resolution of Ground-Tunnel Transient Electromagnetic is much higher than traditional one’s because it is closer to abnormal objects.5. In accordance with damped least-squares inversion method, has realized onedimensional optimization inversion of Transient Electromagnetic. Furthermore, combining the living inversions of the actual data, has verified the correctness and practicability and has laid the foundation for the processing and interpretation of the actual data.