Abstract The full-space transient electromagnetic response of water-filled goaves in coal mines were numerically modeled. Traditional numerical modeling methods cannot be used to simulate the underground full-space transient electromagnetic field. We used multiple transmitting loops instead of the traditional single transmitting loop to load the transmitting loop into Cartesian grids. We improved the method for calculating the z-component of the magnetic field based on the characteristics of full space. Then, we established the full-space 3D geoelectrical model using geological data for coalmines. In addition, the transient electromagnetic responses of water-filled goaves of variable shape at different locations were simulated by using the finite-difference time-domain (FDTD) method. Moreover, we evaluated the apparent resistivity results. The numerical modeling results suggested that the resistivity differences between the coal seam and its roof and floor greatly affect the distribution of apparent resistivity, resulting in nearly circular contours with the roadway head at the center. The actual distribution of apparent resistivity for different geoelectrical models of water in goaves was consistent with the models. However, when the goaf water was located in one side, a false low-resistivity anomaly would appear on the other side owing to the full-space effect but the response was much weaker. Finally, the modeling results were subsequently confirmed by drilling, suggesting that the proposed method was effective.
This work was supported by the National Key Scientific Instrument and Equipment Development Project (No. 2011YQ03013307), the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions, and Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Land and Resources.
Cite this article:
. Three-dimensional numerical modeling of full-space transient electromagnetic responses of water in goaf[J]. APPLIED GEOPHYSICS, 2016, 13(3): 539-552.
[1]
Alford, R. M., Kelly, K. R., and Boore, D. M., 1974, Accuracy of finite-difference modeling of the acoustic wave equation: Geophysics, 39(6), 834−842.
[2]
Fitterman, D. V., and Anderson, W. L., 1987, Effect of transmitter turn-off time on transient soundings: Geoexploration, 24, 131-146.
[3]
Goldman, Y., Hubans, C., Nicoletis, S., et al., 1986, A finite-element solution for the transient electromagnetic response of an arbitrary two-dimensional resistivity distribution: Geophysics, 51(7), 1450−1461.
[4]
Jiang, Z. H., 2008, Study on the mechanism and technology of advanced detection with transient electromagnetic method for roadway drivage face: PhD Thesis, China University of Mining and Technology, Xuzhou.
[5]
Kaufman, A. A., and Keller, G. V., 1983, Frequency and transient soundings: Elsevier, New York.
[6]
Liu, Y., Wang, X. B., and Wang, B., 2013, Numerical modeling of the 2D time-domain transient electromagnetic secondary field of the line source of the current excitation: Applied Geophysics, 10(2), 134−144.
[7]
Oristaglio, M. L., and Hohmann, G. W., 1984, Diffusion of electromagnetic fields into a two-dimensional earth: A finite-difference approach: Geophysics, 49(7), 870−894.
[8]
Raiche, A. P., 1984, The effect of ramp function turn -off on the TEM response of layered earth: Exploration Geophysics, 15, 37− 41.
[9]
SanFilipo, W. A., and Hohmann, G. W., 1985, Integral equation solution for the transient electromagnetic response of a three-dimensional body in a conductive half-space: Geophysics, 50(5), 798−809.
[10]
Sun, H. F., Li, X., Li, S. C., et al., 2013, Three-dimensional FDTD modeling of TEM excited by a loop source considering ramp time: Chinese Journal of Geophysics (in Chinese), 56(3), 1049−1064.
[11]
Wang, T., and Hohmann, G. W., 1993, A finite-difference time-domain solution for three-dimensional electromagnetic modeling: Geophysics, 58(6), 797−809.
[12]
Yan, S., Chen, M. S., and Fu, J. M., 2002, Direct Time-domain numerical analysis of TEM fields: Chinese Journal of Geophysics (in Chinese), 45(2), 275−282.
[13]
Yang, H. Y., Deng, J. Z., Zhang, H., and Yue, J. H., 2010, Research on full-space apparent resistivity interpretation technique in mine transient electromagnetic method: Chinese Journal of Geophysics (in Chinese), 53(3), 651−656.
[14]
Yang, H. Y., and Yue, J. H., 2008, Response characteristics of the 3D Whole-Space TEM disturbed by roadway: Journal of Jilin University(Earth Science Edition)(in Chinese), 38(1), 129−134.
[15]
Yee, K. S., 1966, Numerical solution of initial boundary problems involving Maxwell’s equations in isotropic media: IEEE Transactions on Antennas and Propagation,, 14(3), 302−307.
[16]
Yu, J. C., 2007, Mine transient electromagnetic prospecting: Press of China University of Mining and Technology, Xuzhou.
[17]
Yu, J. C., Wang, Y. Z., Liu, J., and Zeng, X. B., 2008, Time-depth conversion of transient electromagnetic method used in coal mines: Journal of China University of Mining and Technology, 18(4), 546−550.
[18]
Zhdanov, M. S., Lee, S. K., and Yoshioka, K., 2006, Integral equation method for 3D modeling of electromagnetic fields in complex structures with inhomogeneous background conductivity: Geophysics, 71(6), G333−G345.
2016, Vol. 13 
