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| 3D Numerical Simulation to Transient Electromagnetic Method under Effect of Whole-space |
| SUN Yu-guo1, TAN Dai-ming2 |
| 1. China Railway Group Limited, Beijing 100039, China 2. Guangdong Provincial Railway Construction Investment Group Co. Ltd., Guangzhou, Guangdong 510635, China |
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Abstract Research purposes：When the transient electromagnetic method is used for the geological survey in advance for tunnel, the induced electromagnetic field will be generated in front and back of the working faces at the transient moment of disconnecting exciting current. What the receiving coil receives is the fold of the eddy current field of whole space of surrounding rock, different than that of the ground where there is the fold of eddy current of underground half-space. In this paper, the propagation properties of induced eddy current are simulated in whole-space of tunnel without abnormal body and with abnormal body by using ANSYS, and the distribution laws of magnetic flux density along a measuring line with abnormal bodies deflecting from centre and with abnormal bodies at centre are compared. It is significant to the research and wide application of transient electromagnetic method.
Research conclusions：The transient electromagnetic fields in tunnel appears propagation property of "water wave effect" other than "smoking ring effect" on ground. The low conductive body in tunnel obviously changes the time -domain property of eddy current to indicate the induction characteristic of abnormal body. The maximum of magnetic flux density occurs on the other side of centre due to the deflection of abnormal body from the centre line.
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Received: 26 January 2010
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2010, Vol. 27 
