Study On One Dimensional Inversion Of Transient Electromagnetic Effect In Tunnel Whole Space

Transient electromagnetic method is a new method for advanced geological forecast of water-rich adverse geological structure, which is especially sensitive to low resistance type of geological structure. This method gives the advantage to detecting adverse geological structures such as water-rich faults, cave filled with mud and water, broken belt filled with mud and water. At present, One dimensional inversion in half space of the transient electromagnetic has reached the practical stage. If it is applied in tunnel whole-space, the inversion results will have comparatively larger difference from the actual situation. It is urgently needed to start research on transient electromagnetic inversion theory and methods of tunnel whole space. With considering the effect of tunnel whole-space, the formula of one-dimensional half space inversion is modified. The main contents of the thesis are listed as follows:1. This thesis simulate the "smoke ring effect" of electromagnetics by using numerical simulation method and verify the "smoke ring effect" of electromagnetics by qualitative and quantitative means;2. Apply software to build three-dimensional whole-space model and half-space model, analysis and compare the difference and the connection between the whole-space and half-space transient electromagnetic effect;3. Simulate the transient electromagnetic effect of whole-space and half-space by using the symmetry, and modify the one dimension inversion formula by analyzing a large amount of data.Through the analysis and summary to the numerical simulation results, we can know: In half-space, the induced eddy currents spread downward and outward like "smoke ring", while in the whole-space it spread outward based on the transmitting coil as the center; The transient electromagnetic effect is obvious at back of tunnel face in whole-space of tunnel, while there is no induction eddy current in the half-space; The transient electromagnetic effect in whole-space is more stronger than that in half-space, and there is a multiple relationship in a certain range.